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Use of Four Predictive Screening Variables for Determination of Sacroiliac Joint Dysfunction in Adolescent Soccer Athletes Use of Four Predictive Screening Variables for Determination of Sacroiliac Joint Dysfunction in Adolescent Soccer Athletes Brian Hanson Follow this and additional works at: https://researchrepository.wvu.edu/etd Recommended Citation Hanson, Brian, "Use of Four Predictive Screening Variables for Determination of Sacroiliac Joint Dysfunction in Adolescent Soccer Athletes" (2018). Graduate Theses, Dissertations, and Problem Reports. 5759. https://researchrepository.wvu.edu/etd/5759 This Thesis is protected by copyright and/or related rights. It has been brought to you by the The Research Repository @ WVU with permission from the rights-holder(s). You are free to use this Thesis in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you must obtain permission from the rights-holder(s) directly, unless additional rights are indicated by a Creative Commons license in the record and/ or on the work itself. This Thesis has been accepted for inclusion in WVU Graduate Theses, Dissertations, and Problem Reports collection by an authorized administrator of The Research Repository @ WVU. For more information, please contact researchrepository@mail.wvu.edu. Use of Four Predictive Screening Variables for Determination of Sacroiliac Joint Dysfunction in Adolescent Soccer Athletes Brian Hanson, ATC, CES Thesis submitted to the College of Physical Activity and Sports Sciences At West Virginia University In partial fulfillment of the requirements for the degree of Master of Science in Athletic Training Michelle A. Sandrey, PhD, ATC, Chair Jean L. McCrory, PhD Benjamin Moorehead, MD Department of Sport Sciences Morgantown, West Virginia 2018 Keywords: sacroiliac joint dysfunction, adolescent soccer athlete, functional movement screen, injury risk Copyright 2018 Brian Hanson i ABSTRACT Use of Four Predictive Screening Variables for Determination of Sacroiliac Joint Dysfunction in Adolescent Soccer Athletes Brian Hanson, ATC, CES Context: Chronic onset of sacroiliac joint dysfunction (SIJD) is increasing in adolescent athletic populations including soccer. However, there is currently no pre-season screening tool for SIJD in this population. There are variables that are currently associated with SIJD, however, it is unknown if these variables developed into a screening tool can accurately predict the risk of sustaining SIJD. Objective: The purpose of this study was to create an effective screening tool for SIJD in adolescent soccer athletes and establish predictive values for SIJD injury risk. Design: A retrospective exploratory study to screen for risk factors contributing to SIJD in the adolescent soccer athletes. Setting: The testing took place in an athletic training facility at a mid Atlantic high school. Only one clinician administered the testing procedures. Patients or other participants: This study included members of the varsity and junior varsity boys’ (n = 6, 16.33±1.37 yrs, 176.50±6.98 cm, 72.12±9.92 kg) and girls’ (n = 14, 16.00±1.11 yrs, 165.93±6.39 cm, 61.11±6.92 kg) soccer teams from one high school in north central West Virginia. All participants were members of these teams with a sports physical on file. Inclusion criteria included those subjects who are healthy, have no disorders affecting ability to perform any of the tests included in this study, no history of acute injury to the lower extremity or back in the past six months, and no history of surgeries to the core or back within the past year. Exclusion criteria included subjects who have a history of surgery to the core or back within the past year, and those who have a disorder affecting ability to perform any of the tests included in this study. Interventions: Each participant performed during one testing session the Functional Movement Screen (FMS), including all 7 functional movements and the 3 clearing tests, active knee extension test, Palpation Meter (PALM) measurement for pelvic angle, and goniometry assessment of active hip range of motion (flexion/extension/abduction/adduction /internal rotation/external rotation). Main outcome measures: The dependent variables that were measured are the final composite score of the FMS, angle measurement in degrees from the active knee extension test, pelvic tilt angle in degrees from the PALM, and angle measurement in degrees for active hip flexion, extension, abduction, adduction, internal rotation, and external rotation. Results: A significant correlation with large strength (PCC = 0.545, p = .013) was found between SIJ injury and active hip abduction. A significant correlation with large strength (PCC = 0.732, p <.01) was found between the PALM and active hip extension. A significant correlation with medium strength (PCC = 0.473, p = .035) was found between the AKET and active hip flexion. One model in the binary logistic regression created a best fit with an odds ratio of 1.115 (CI95 = 1.003, 1.239, p = .044) with the variables of SIJ injury and active hip abduction. Two nonsignificant models with moderate odds ratios were produced for the PALM (OR = 1.141, CI95 = .841, 1.547, p = .397) and years playing soccer (OR = 1.319, CI95 = .854, 2.036, p = .212). A stepwise binary logistic regression created a best fit model with an odds ratio of 1.168 (CI95 = 1.004, 1.359, p = .045) that included both active hip abduction and the FMS to detect and SIJ injury. Conclusion: The results from this study indicate that active hip abduction will significantly predict an SIJ injury. Years of playing soccer, the FMS, and pelvic positioning may also be clinically useful assessments to predict an SIJ injury. ii ACKNOWLEDGEMENTS I would like to start by thanking my parents, Steve and Marilu. They have provided me with endless support and discipline throughout my entire academic career. If it weren’t for them and the countless opportunities they provided me I would not be where I am today. I would like to thank my two older sisters, Jackie and Stephanie. They have always been the perfect role models, not only as students, but by showing me what it takes to be a good person. The high level of success they have achieved in life continues to fuel my ambition to make myself a better person and for that I am forever grateful. I would like to thank the rest of my family. It has been tough living away from all of you for the first time and in a new state for the past two years, but your support has been unwavering. I would like to thank my friends, both the new ones made here, and the ones still back home. You all have kept me feeling sane while balancing the rigors of graduate school and work. Thanks to those who blew away any expectations and came to visit me in the mountains. Thank you to my committee members, Dr. Benjamin Moorehead and Dr. Jean McCrory. I am very appreciative of the time and effort you have put into this process. A giant thanks to my committee chair and graduate advisor, Dr. Michelle Sandrey. You certainly pushed me beyond my previous limits in the realm of research and writing. The amount of time spent reading my drafts, making suggestions, and meeting with me did not go unnoticed. Thank you for all the challenges provided both inside and outside the classroom. To my clinical supervisor at HealthWorks, Mike Casselman, it has been the utmost pleasure to serve under you for the past two years. Your guidance and expertise has assisted me to improve as a clinician. Best of luck with your new job and all future endeavors. To my athletic director, Jeff Bailey. Thanks for being the world’s best AD, you have certainly made my job easy. To my soccer coaches, Graham Peace, Kat Devlin, and Dustin Talton at University High School. You all have been a pleasure to work with and helped with my transition as a newly certified athletic trainer. I appreciate the trust you had in me from day one to always give the best care to our student athletes. To my subjects/athletes. You all have kept me on my toes and kept me feeling young these past two seasons. Thank you for all the laughs and success on the field. Lastly, I want to thank everyone else I did not mention that has helped me get to this point. I am incredibly appreciative of the impact everyone has made on my life. iii TABLE OF CONTENTS ACKNOWLEDGMENTS………………………………………………………………………..iii LIST OF TABLES………………………………………………………………………………..v INTRODUCTION………………………………………………………………………………...1 METHODS………………………………………………………………………………………..4 RESULTS………………………………………………………………………………………..15 DISCUSSION……………………………………………………………………………………18 CONCLUSION…………………………………………………………………………………..28 REFERENCES…………………………………………………………………………………..30 APPENDICES…………………………………………………………………………………...37 APPENDIX A THE PROBLEM………………………………………………………..38 APPENDIX B LITERATURE REVIEW……………………………………………….47 APPENDIX C ADDITIONAL METHODS…………………………………………….72 APPENDIX D ADDITIONAL RESULTS…………………………………………….106 APPENDIX E RECOMMENDATIONS FOR FUTURE RESEARCH………………110 ADDITIONAL REFERENCES………………………………………………………………...111 iv LIST OF TABLES TABLE B1. Ligamentous/Fascia Support Structures of the Sacrum……………………………49 TABLE B2. Muscle Origin/Insertion/Action/Innervation Surrounding the SIJ…………………51 TABLE B3. Measurement Techniques for Hamstring Length/Extensibility……………………64 TABLE B4. Hip Range of Motion……………………………………………………………….69 TABLE C1. Informed Parental or Guardian Consent……………………………………………72 TABLE C2. Informed Assent……………………………………………………………………78 TABLE C3. Informed Consent 18 Years or Older………………………………………………82 TABLE C4. Subject Demographics……………………………………………………………...88 TABLE C5. Verbal Instructions for Functional Movement Screen……………………………..89 TABLE C6. Functional Movement Screen Scoring Procedures………………………………...93 TABLE C7. Active Knee Extension Test………………………………………………………..97 TABLE C8. Pelvic Positioning…………………………………………………………………..98 TABLE C9. Hip Range of Motion – Goniometer………………………………………………100 TABLE C10. Functional Movement Screen Scoring Sheet……………………………………104 TABLE C11. Data Collection Sheet……………………………………………………………105 TABLE D1. Descriptive Statistics (Means ± SD) for Subject Demographics………………….106 TABLE D2. Descriptive Statistics (Means ± SD) for All Screening Variables………………...106 TABLE D3. Descriptive Statistics (Means ± SD) for Subject Demographics and SIJ Injury….107 TABLE D4. Descriptive Statistics on Means and SD for Screening Variables and SIJ Injury...107 TABLE D5. Pearson Product Correlations of Demographic Data to SIJ Injury……………….107 TABLE D6. Pearson Product Correlations of Predictive Variables to SIJ Injury……………...108 TABLE D7. Crosstab of Lower Extremity (DS, IL, HS) Movements from the FMS………….108 v LIST OF TABLES TABLE D8. Binary Logistic Regression Model for Screening Variables Associated with the Occurrence of a SIJ Injury……………………………………………………………………...109 TABLE D9. Stepwise Binary Logistic Regression Model for Screening Variables Associated with SIJ Injury…………………………………………………………………………………..109 vi INTRODUCTION Low back pain (LBP) has been shown to affect up to 80% of the general population at some point in their lifetime.1,2 Although LBP is a main symptom, sacroiliac joint dysfunction (SIJD) often clinically presents with LBP, thus leading to the conclusion that LBP can be caused by various injuries. Specifically, amongst the adolescent population, prevalence of LBP has reported to range from 30% to 74%.3,4 Low back pain, which can be caused by SIJD, was found to increase with age amongst the adolescent population. Increases in LBP are evident starting with 1% at seven years of age, to 17% at twelve years of age, and climbs to 53% at 15 years of age.5 Further, prevalence amongst adolescents with SIJD pain has been reported to range from 13% to 30% of all injuries with LBP as a symptom.6,7 Historically SIJD has been seen in young athletes who have sustained some form of mild trauma, however, more athletes now are experiencing a chronic onset.8 SIJD is commonly seen in sports with unilateral and repetitive biomechanical forces, such as kicking in soccer. Although there is little research on specifically SIJD, there is an apparent link between LBP and SIJD resulting in play time loss for athletes, specifically soccer. In one study,9 LBP was found to be the most prevalent previous overuse injury with an incidence of 28% among soccer players. At least 60.6% of soccer players (n=190) were found to have experienced LBP in their lifetime, and 56.9% felt it in the previous 12 months, resulting in 27.7% missing training from injury.10 Another study11 reported 54.4% of futsal players experiencing LBP in their lifetime, and 25.7% had absence from training sessions due to LBP. The nature of soccer places high intensity forces on the lower extremities that are often unilaterally dominant. These forces are transferred superiorly to the trunk through the sacrum and SIJ acting as the gateway. The biomechanical demands of playing soccer, including bending 1 and twisting of the trunk and variable lateral movement are a reason for SIJD to occur at such a high rate.11,12 With consideration of the biomechanics and prevalence of SIJ in soccer athletes, a screening tool should be created to evaluate potential risk factors. Four different components that have the potential to biomechanically evaluate SIJD prevalence are the Functional Movement Screen (FMS), pelvic positioning, hamstring length, and hip range of motion (ROM). The FMS is a preexisting screening tool that investigates seven fundamental movement patterns (deep squat, hurdle step, active straight leg raise (ASLR), rotary stability, inline lunge, shoulder mobility, and trunk stability push up). Currently there is little research available on whether the FMS subtests correlate with predicting SIJD. Only one study13 was conducted comparing FMS with chronic LBP patients to healthy controls. The authors13 reported that the chronic LBP patients scored significantly lower on the deep squat, hurdle step, ASLR, and rotary stability compared to the healthy controls. The results of this study indicate that those four tests of the FMS could contribute to accurately predicting SIJD. The movement of the innominates in both static and dynamic positions directly affects the movement of the sacrum, and potentially the motion that occurs at the SIJ. Malalignment of the innominates has the potential to negatively impact the SIJ. Pelvic asymmetry has been shown to contribute to altered lower extremity mechanics and contribute to SIJD in the frontal and sagittal planes.14 Athletes who participated in a sport with lateral movements, much like a goalkeeper or defender in soccer, would over time develop pelvic asymmetry problems leading to an increased incidence in back pain.15 Hamstring tightness in individuals with LBP could be a compensatory mechanism to weak gluteal muscles, which in turn decrease the compression stability mechanism of the SIJ.16 19 Subjects with SIJD had significantly shorter hamstring muscle length in individuals with 2 gluteal weakness compared to those who did not have gluteal weakness.20 In soccer players a natural hip adaptation may occur resulting in unilateral hip ROM deficits from a repetitive kicking motion. Hip ROM is well cited in the literature in contributing to SIJ motion.15,21,22 Hip rotation was a strong predictor for innominate angle, which in turn affects the motion occurring at the SIJ.23 The link between hip internal and external rotation and SIJD was also evaluated. Individuals with LBP including some with designated SIJ pain demonstrated a hip asymmetry of decreased internal rotation on the affected side compared bilaterally to the unaffected side with patients who had specific SIJ pain.21 Using a control group design, subjects with non-specific low back pain were compared to healthy controls to analyze hip rotation and extension. There was a difference in hip extension where the controls had greater hip extension then those with LBP.22 There is a plethora of knowledge on the SIJ in terms of anatomy, biomechanics, treatment, and rehabilitation. There is also a great deal of research on SIJD and LBP in athletes in the adult population across a wide span of sports. Conversely, there is a lack of knowledge on SIJD in adolescent athletes. Pain caused by SIJD historically has been more prominent in the adult population, however it has become increasingly prevalent in the adolescent population for reasons that are not well understood.2 With the increase of SIJD incidence in the adolescent population, some type of screening tool must be developed to assess predictive factors of SIJD, especially in soccer athletes. Currently there is no constructed clinical screening tool to assess predictive factors for SIJD in the adolescent soccer athlete population. With no known screening tool available, four different biomechanical and functional components that should be considered are the Functional Movement Screen (FMS), pelvic positioning, hamstring length, and hip ROM. 3 Thus, the purpose of this study was to create an effective screening tool for SIJD in adolescent soccer athletes and establish predictive values for SIJD injury risk. METHODS Design This study was a retrospective exploratory screening study to determine SIJD risk in adolescent soccer athletes. The independent variable was whether the athlete sustained a SIJ injury over the course of the past season. The dependent variables were the composite score of the FMS, the angle taken from the active knee extension test, pelvic angle measurement of both innominates, and goniometric angle hip range of motion measurements (flexion, extension, abduction, adduction, internal rotation, external rotation). These dependent variables were evaluated to predict potential SIJD injury risk. Subjects This study included members of the varsity and junior varsity boys’ and girls’ soccer teams from a high school in north central West Virginia. Twenty subjects (14 females, 6 males, 16.10±1.17 yrs, 169.1± 8.09 cm, 64.41± 9.25 kg) were recruited and completed all procedures of this study. Inclusion criteria included those subjects who are healthy, have no disorders affecting ability to perform any of the tests included in this study, no history of acute injury, other than a SIJD, to the lower extremity or back in the past six months, and no history of surgeries to the core or back within the past year. The subject had a sport physical on file and were currently a member of either the boys’ or girls’ soccer team at one high school during this past sports season. Exclusion criteria included subjects who have a history of surgery to the core or back within the past year, and those who have a disorder affecting ability to perform any of the tests 4 included in this study. This study was approved by the Institution’s Office of Research Compliance. Instruments Functional Movement Screen (FMS): The FMS was developed by Cook in an effort to connect pre-participation medical screening and performance testing.24-28 This screening was created in attempt to detect deficiencies by incorporating the mobility of the kinetic chain and stability necessary for performance. Although inconclusive results on the validity of the FMS to screen or detect movement deficiencies was evident, the procedures reproduced with consistency was apparent.28-33 Intra-rater reliability has been reported to range from ICC = 0.74 to 0.99.33 Thus, clinicians frequently use the FMS as a screening tool and despite not being the original intent of the FMS, professionals in the field of exercise, sport performance, and sport medicine use the FMS to analyze the movement capabilities of athletes and those who are at risk for injury. This interpretation of the FMS has been heavily investigated and the results show that athletes who score 14 or less points on the FMS are at an increased risk for injury.34-39 While a lot of research exists on collegiate aged athletes, there is little research that exists investigating the use of the FMS as an injury prediction tool on adolescent soccer athletes. Active knee extension test: Hamstring length measures the dynamic lengthening ability of the hamstring muscle group as the origin rests in a fixed position while the distal portion is in movement. It has been determined that the active knee extension test provides the best objective measurement of hamstring length due to the ease of measurement and excellent reliability of the test.40-43 An average range of motion for this test in normal healthy adults was shown to have a deficit of full extension of 35.6 +/- 10.4˚ for men, and 27.1 +/- 13.5˚ for women.44 In 5 comparison, elite track and field athletes (n = 127) established a normal value ranging between 72.3˚ and 73.9˚ with the active knee extension test.45 Palpation meter (PALM): The PALM is a device with a built in inclinometer that has been used to objectively measure pelvic angle. Despite little use in the adolescent population the PALM has shown to be both valid and reliable in measuring pelvic angles in the sagittal plane.46 48 A neutral pelvis has been established at 0 degrees with positive degrees describing an anterior innominate tilt, and negative degrees describing a posterior innominate tilt.47 Normative values in an asymptomatic adult population have been reported to be 6.49˚ in males and 6.78˚ in females.47 Hip range of motion: The hip has six degrees of freedom allowing for flexion, extension, abduction, adduction, internal rotation, and external rotation. Measurement of these movements can be assessed using a goniometer providing an angle in degrees. Goniometer use for angle measurement has been shown to be both reliable and valid in healthy populations and those with chronic LBP.49-51 Average hip range of motion values in males and females aged 11 to 17 years of age have been established. Results for males and females, respectively are flexion (113˚, 120˚), extension (15˚, 22˚), abduction (34˚, 44˚), adduction (14˚, 17˚), internal rotation (35˚, 35˚), and external rotation (40˚, 46˚).52 Procedures Before the screening tool procedures started, an informational meeting took place with the subjects and their parents. In this meeting, the informed parental consent form with HIPAA included (Table C1), informed assent form (Table C2), the informed consent form with HIPAA for subjects 18 and older (Table C3), and the demographic questionnaire (Table C4) were discussed. The informed consent forms with HIPAA and the demographic questionnaire were 6 completed during this informational meeting. After subjects and parents completed the necessary paperwork, screening tool procedures were explained. Instructions for the testing procedures were explained to all subjects during the informational meeting and before performing the tests. Those subjects who met all inclusion criteria were invited to participate in the study. Times were established for subjects to meet with the researcher once within a three-week period to complete all components of the screening tool; approximately one 30-minute session. The participants were permitted to engage in normal daily routines without limitations. Participants were allowed to wear self-selected athletic shoes and athletic clothes (shorts and a t-shirt) for the FMS, while shoes and socks were removed for the active knee extension test, pelvic positioning measurements, and hip range of motion measurements. All screening tool procedures were performed in the athletic training room and auxiliary space at one Mid-Atlantic high school to serve as an environmental control. Administration and supervision of all testing was completed by the primary researcher. Functional Movement Screen (FMS): Standard FMS procedures (Table C5, Table C6) were used as previously defined by Cook.25 A script was read (Table C5) to ensure understanding of the tested movements. Participants were not “cued” of their movements. Each participant was instructed to perform the 7 fundamental movements and 3 clearing tests (Table C6). Individuals were limited to a maximum of three trials for each movement, and an extensive warm up was not included. A movement was given a score between 0 and 3. A score of 1 indicates the inability to complete the movement, 2 represents compensation while completing a movement, and 3 signifies a correct completion of the movement without compensation. The raw score was used to denote right and left side scoring. The final score denoted the overall score for 7 the test. The lowest score for the raw score (each side) carried over to give a final score for the test. The first movement in the FMS (Table C6) was a deep squat designed to assess bilateral, symmetrical, functional mobility of the hips, knees, and ankles. A dowel was held overhead to assess bilateral symmetrical mobility of the shoulders and thoracic spine. The participant assumed a shoulder width apart stance and grasped the dowel so that the arms formed a 90 degree angle at the head. The participant then pressed the dowel overhead with the elbows in full extension. The participant was instructed to descend as far as possible into a squat while keeping heels on the ground and maintaining an upright torso. A one second pause at the bottom of the squat was completed before returning to the start position. The participant had a maximum of three trials to complete the movement to the best of his/her ability. The second movement in the FMS (Table C6) was the hurdle step. This movement is designed to assess mobility and stability of the hips, knees, and ankles. The height of the hurdle was set to the height of the participant’s tibial tuberosity. The participant (while holding a dowel behind the head and across the shoulders) was instructed to step over the hurdle with one leg, touch the ground on the other side of the hurdle (without accepting weight), and then return the leg back over the hurdle. This test was completed bilaterally. The participant had a maximum of three trials to complete the movement to the best of his/her ability. The third movement of the FMS (Table C6) was the in-line lunge. This movement is designed to assess quadriceps flexibility, hip mobility, and stability, and bilateral ankle and knee stability. The participant stood on a 2 x 6 board and held a dowel behind the back. The dowel maintained three points of contact (base of skull, thoracic spine, and sacrum) throughout the lunge. The opposite hand of the front foot was used to grasp the dowel at the head while the 8 other hand was placed on the dowel in the lumbar spine. The height of the tibial tuberosity was used as the distance between the two feet. The back knee touched the board behind the front foot and the feet were kept in the sagittal plane during the lunge. This test was assessed bilaterally. The participant had a maximum of three trials to complete the movement to the best of his/her ability. The fourth movement of the FMS (Table C6) was the shoulder mobility test. This movement is designed to assess shoulder range of motion. The tester measured (in inches) the length of the participant’s hand from the crease of the wrist to the end of the third finger. The participant was then instructed to close the fist, and maximally adduct, extend, and internally rotate with one shoulder and maximally abduct, flex, and externally rotate the other. The flexed shoulder was the side that was scored. The tester then measured the distance between the two fists. The test was assessed bilaterally. The participant had a maximum of three trials to complete the movement to the best of his/her ability. The shoulder clearing test (Tale C6) was performed at the end of the shoulder mobility test. This movement was not scored but was used to observe a pain response. This clearing test is necessary to detect impingement symptoms that can go undetected with the shoulder mobility test. The individual was instructed to place the hand on the opposite shoulder and attempt to point the elbow upward. If pain was produced, a score of zero was given for the test. The clearing test was performed bilaterally. The fifth movement in the FMS (Table C6) was the active straight leg raise. This movement is designed to assess active flexibility of the hamstrings and gastroc-soleus complex while maintaining a stable pelvis and core. The participants were instructed to lie on the back with the 2 x 6 board under the knees with the leg straight. The leg that was not tested remained in 9 contact with the floor with the foot in a dorsiflexed position. The tester then identified the midpoint between the ASIS and midpoint of the patella. A dowel was then placed perpendicular to the floor at the measured midpoint. While maintaining contact with the floor through the head and lower back, the participant was instructed to raise the test leg with a dorsiflexed ankle and extended knee as far as possible. If the malleolus did not pass the dowel, the dowel was moved in line with the malleolus of the test leg and scored per the criteria. This test was performed bilaterally. The participant had a maximum of three trials to complete the movement to the best of his/her ability. The sixth movement in the FMS (Table C6) was the trunk stability push-up. This movement is designed to assess trunk stability while a closed-chain upper body motion is completed. The participant assumed a prone position with the hand spaced shoulder-width apart and the feet together. Females were instructed to place thumbs in line with the chin. Males were instructed to place thumbs in line with the forehead. The participant was then instructed to lift the body as a unit with the knees extended and ankles dorsiflexed to complete one push-up. If the participant was not able to complete the push-up the hand position was moved level with the chin for males, and moved level to the clavicle for females. The participant had a maximum of three trials to complete the movement to the best of his/her ability. The spinal extension clearing test (Table C6) was performed after the trunk stability push-up. This movement was not scored but was used to observe a pain response. The clearing test is necessary to detect back pain that can go undetected with movement screening. The participant was instructed to perform a press-up in the push-up position. If pain was produced, a score of zero was given for the test. 10 The seventh movement in the FMS (Table C6) was the rotary stability test. The participant was instructed to assume a quadruped position with both hands and both feet on the ground at relatively 90 degree angles (shoulders relative to the upper torso; hips/knees relative to the lower torso). The 2 x 6 board was placed between the knees and hands so that both the hands and knees are touching the board. The participant was then instructed to lift the arm and leg (flexes shoulder, extends hip) on the same side and attempt to touch the knee and elbow together. If the participant was unable to complete such a repetition, the pattern changed to a diagonal pattern (opposite arm and leg). This test was performed bilaterally. The participant had a maximum of three trials to complete the movement to the best of his/her ability. The spinal flexion clearing test (Table C6) was performed at the end of the rotary stability test. This movement was not scored, but was used to observe a pain response. The purpose of this clearing test is necessary due to back pain going undetected by movement screening. Spinal flexion was cleared when a quadruped position was assumed, and then rocked back to touch the buttocks to the heels and chest to the thighs. Hands remained in front of the body, reaching out as far as possible. If pain was produced, a score of zero was given for the test. Active knee extension test: The next measurement in the screening tool was hamstring length. Procedures that have been previously described were used for the active knee extension test and are outlined in Table. C7.42,53 The subject was supine on the table and was instructed to flex the testing extremity to 90 degrees and maintain that position. The investigator then secured the non-tested extremity to the table using a strap across the lower third of the thigh. The subject was then instructed to extend the knee as far as possible while keeping the foot in a relaxed position and held that position for approximately five seconds. The investigator then aligned the fulcrum of the goniometer to the midpoint of the lateral joint line, aligned the stationary arm to 11 the greater trochanter of the femur, and aligned the movable arm to the lateral malleolus of the fibula. An angle measurement in degrees was taken from the goniometer. This test was performed bilaterally. The participant had two trials bilaterally, one after the other, and the average of both was taken. Palpation meter (PALM): Procedures that have been previously described were used for assessment of pelvic angle and are outlined in Table C847,48 The investigator created markings on the floor that are 30 cm apart that the participant stood on. Participants adopted an erect posture and kept arms crossed over the chest. Participants were instructed to look at a fixed point ahead of them as to help control for postural sway. Palpation by the investigator was performed over the clothes. Palpation began by locating the ASIS bringing the thumbs inferior to superior and marked the most prominent protrusion with an adhesive felt pad. The investigator then located the PSIS by following the iliac crest with the thumbs first posteriorly, then superior and laterally from the sacrum and marked the most prominent protrusion with an adhesive felt pad. The subject held the pads in place as to limit movement of the pads over the athletic shorts. The calipers were placed over the marked ASIS and PSIS on the ipsilateral side and compressed to a firm resistance. The angle of inclination was read from the inclinometer built into the PALM device. Positive degrees were used to describe anterior innominate tilts, and negative degrees were used to describe posterior innominate tilts. The test was performed bilaterally. The participant performed two trials bilaterally, one after the other, and the average of both was taken. Hip range of motion: Active hip range of motion was assessed by a goniometer for hip flexion, extension, abduction, adduction, internal rotation, and external rotation. These motions and the goniometer measurements for each are outlined in Table C9. The tests were performed 12 bilaterally for all six motions. The participant performed two trials bilaterally, one after the other, and the average of both was taken. Hip flexion measurements52 were taken with the participant lying in supine. The participant was then instructed to actively flex the hip as far as possible with the knee in a flexed position. The fulcrum of the goniometer was placed at the greater trochanter of the femur, the stationary arm was aligned parallel to the trunk of the participant, and the movement arm was aligned with the midpoint of the lateral joint line. Angle measurements were taken from the goniometer in degrees. Hip extension measurements22,52 were taken with the participant lying prone with the extremity extended beyond the table. The participant was then instructed to actively extend the hip as far as possible. The fulcrum of the goniometer was placed at the greater trochanter of the femur, the stationary arm was aligned parallel to the trunk of the participant, and the movement arm was aligned with the midpoint of the lateral joint line. Angle measurements were taken from the goniometer in degrees. Hip abduction measurements23,52 were taken with the participant in a side lying position. The participant was then instructed to actively abduct the hip as far as possible. The fulcrum of the goniometer was placed at the ASIS of the tested leg. The stationary arm was aligned with the contralateral ASIS, and the movement arm was aligned with the midpoint of the patella. Angle measurements were taken from the goniometer in degrees. Hip adduction measurements52 were taken with the participant in a standing position. The participant was then instructed to actively adduct the hip as far as possible. The fulcrum of the goniometer was placed at the ASIS of the tested leg. The stationary arm was aligned with the 13 contralateral ASIS, and the movement arm was aligned with the midpoint of the patella. Angle measurements were taken from the goniometer in degrees. Hip internal rotation52 was taken with the participant in a short-seated position. The participant was then instructed to actively internally rotate the hip as far as possible. The fulcrum of the goniometer was placed at the center of the patella. The stationary arm was aligned horizontally with the table, and the movement arm was aligned with the shaft of the tibia. Angle measurements were taken from the goniometer in degrees. Hip external rotation23,52 was taken with the participant in a short-seated position. The participant was then instructed to actively externally rotate the hip as far as possible. The fulcrum of the goniometer was placed at the center of the patella. The stationary arm was aligned horizontally with the table, and the movement arm was aligned with the shaft of the tibia. Angle measurements were taken from the goniometer in degrees. All data from these measurements were recorded on the FMS scoring sheet (Table C10) and the data collection sheet (Table C11). Statistical Analysis Descriptive analysis consisted of means and standard deviations of all subjects for demographic information, FMS composite scores, active knee extension test, PALM, and hip range of motion measurements. To determine the strength of the relationship between all variables, Pearson’s Correlation Coefficient was used. Relationship strengths are defined as small (.1-.29), medium (.3-.49), and large (.5-1.0).54 To determine predictors of injury other statistics including binary logistic regression, Cox & Snell R2, Nagelkerke R2, and odds ratio were used with 95% Confidence Intervals. A binary logistic regression was used producing a Cox & Snell pseudo R2, Nagelkerke pseudo R2, and odds ratio statistics. The higher the Cox & 14 Snell pseudo R2, and Nagelkerke pseudo R2 the better the model fits the data. The ability to predict outcomes or characteristics that may predispose an athlete to sustain a SIJD can be useful both clinically and in applied settings. Eleven models were selected to indicate best fit. The first model compared FMS composite scores and SIJ injury history. The second model compared the average of both extremities’ active knee extension test and SIJ injury history. The third model SIJ compared the average of both innominates’ pelvic angle tilt measurement from the PALM and SIJ injury history. The fourth through ninth model compared the average angle for both extremities for active hip flexion, extension, abduction, adduction, internal rotation, and external rotation and SIJ injury history. The tenth model compared years of playing soccer and SIJ injury history. The eleventh model compared current athletic participation and SIJ injury history. A stepwise binary logistic regression was analyzed to investigate any interaction between the previous eleven variables. The P value was set at P = 0.05 for all analyses. IBM/SPSS software (IBM/SPSS, Inc., Chicago, IL) version 24.0 was used for all analyses. RESULTS Demographic Data Fourteen females (age = 16.00±1.11 yrs, height = 165.93±6.39 cm, mass = 61.11±6.92 kg) and six males (age = 16.33±1.37 yrs, height = 176.50±6.98 cm, mass = 72.12±9.92 kg) adolescent soccer athletes who participated on the varsity and/or junior varsity teams at one north central West Virginia High School volunteered for this study. Three (15%) of the subjects were in the freshman class, three (15%) of the subjects were in the sophomore class, ten (50%) of the subjects were in the junior class, and four (20%) of the subjects in the senior class. None of these subjects had an injury status that prevented them from any of the study measurements at the time 15 of data collection. Five (25%) of these athletes sustained a SIJ injury over the course of the previous soccer season. Other injuries that occurred over the course of the season were ankle injuries (n=3, 15%), knee injury (n=1, 5%), and hamstring injury (n=1, 5%). None of these players missed significant time from these injuries, and therefore were not excluded from the study. Position was divided into four categories, keeper (n=1, 5%), defense (n=8, 40%), midfield (n=8, 40%), and forwards (n=3, 15%). Descriptive subject data including age, height, weight, years playing soccer, playing soccer year-round, and current athletic activity is presented in Table D1. Descriptive subject data on the means and standard deviations of the screening variables for male and female participants are presented in Table D2. Descriptive subject data on demographics and the means and standard deviations of the screening variables between those who have an SIJ injury and those who do not are presented in Tables D3-D4. Correlation Coefficients Pearson correlation coefficients were run for the relationships between demographic data and SIJ injury (Table D5) and the relationships between the predictive variables and SIJ injury (Table D6). No significant correlations were found between SIJ injury, years playing soccer, and current athletics participation. Small to large correlations were present among the predictive screening variables and SIJ injury. A significant correlation with large strength (PCC = 0.545, p = .013) was found between SIJ injury and active hip abduction. As hip abduction increased so did the occurrence of a SIJ injury. A significant correlation with medium strength (PCC = 0.473, p = .035) was found between the AKET and active hip flexion. As hip flexion increased so did the AKET results. A significant correlation with large strength (PCC = 0.732, p < .01) was found between the PALM measurement and active hip extension. As the pelvis was tilted anteriorly active hip extension increased. 16 Cross Tabs of Lower Extremity FMS Movements A cross tabs of the three lower extremity based movements, deep squat, inline lunge, and hurdle step, from the FMS was run with SIJ injury occurrence set as the dependent variable. This information is presented in Table D7. The cross tabs revealed that those who did and did not have an SIJ injury scored similarly on the deep squat and hurdle step. The inline lunge, however, demonstrated that those without a SIJ injury performed well, whereas, the majority with a SIJ injury had decreased performance. Logistic Regression and Odds Ratios A binary logistic regression was run producing a Cox & Snell pseudo R2 and Nagelkerke pseudo R2 statistics. The higher the Cox & Snell pseudo R2 and Nagelkerke pseudo R2 statistics, the better the model fits the data. One model provided the best fit. The 2 x 2 contingency table using the variables SIJ injury and active hip abduction produced a Cox & Snell R2 (.282), Nagelkerke R2 (.418), and an odds ratio of 1.115 (CI95 = 1.003, 1.239, p = .044). This logistic model “moderately” fits the data and accounts for 28.2% - 41.8% of the variance of hip abduction being able to predict SIJ injury or not. The odds ratio for hip abduction increased the risk of SIJ injury by 11.5%. All other models did not produce statistically significant results and are presented in Table D8. Two nonsignificant models with moderate odds ratios were produced for the PALM (OR = 1.141, CI95 = .841, 1.547, p = .397) and years playing soccer (OR = 1.319, CI95 = .854, 2.036, p = .212) The models using the variables 1) SIJ injury and FMS composite scores; and 2) SIJ injury and years playing accurately predicted one subject with SIJ, however, did not produce statistically significant results for the entire model. A step wise binary logistic regression was run producing a Cox & Snell pseudo R2 and Nagelkerke pseudo R2 statistics to investigate interaction affects within and between the 17 variables. Two models provided the best fit. The 2 x 2 contingency table using the variables SIJ injury and active hip abduction produced the same outcome listed above. The second model included three variables, SIJ injury history along with hip abduction and FMS composite scores. All other variables were not found to be included into the model equation. This model produced a Cox & Snell R2 (.426), Nagelkerke R2 (.631), and an odds ratio of 1.168 (CI95 = 1.004, 1.359, p = .045). This logistic model “moderately” fits the data and accounts for 42.6% - 63.1% of the variance of hip abduction being able to predict SIJ injury or not. The odds ratio for hip abduction and FMS increased the risk of SIJ injury by 16.8%. The interaction term was not significant (OR = 1.003, CI95 = .999, 1.007, p = .095) between active hip abduction and FMS composite scores. All stepwise binary logistic regression statistics are presented in Table D9. DISCUSSION The main purpose of this study was to determine screening variables that can effectively predict SIJD for adolescent soccer athletes. The results of this analysis showed that there were large statistically significant correlations between active hip abduction and SIJ injury occurrence, and PALM measurement and active hip extension. There was also a medium statistically significant correlation between the AKET and active hip flexion. One model, active hip abduction, of the binary logistic regression produced a statically significant finding. The model reflected the concept that those with the highest angle of active hip abduction had an increased risk of an SIJ injury by 11.5%. All other models did not produce statistically significant results. A stepwise binary logistic regression produced another statistically significant model that included the FMS with active hip abduction. In this model, those with the highest angle of active hip abduction, and the lowest FMS composite scores had an increased risk of SIJ injury by 16.8%. These findings suggest that ROM, especially hip abduction, and FMS scores may be an 18 important consideration in deciding which variables to evaluate, as well as to consider for prevention and intervention strategies. As this is the first study to evaluate potential predictor variables for SIJD in adolescent soccer players, the findings from the current study cannot be directly compared with the prior studies that evaluated risk factors and the effect on low back pain in adolescents55 or the FMS in relation to low back pain.13 However, the results from those studies provide a basis as to why certain variables should be considered. Injury Demographics and SIJ Injury Among the 20 subjects that volunteered for this study, five had an SIJ injury, all females, over the course of the past soccer season. The higher incidence of SIJ injury in females compared to male counterparts may partially be explained by anatomical differences between the two sexes. In males, the articular surface between the sacrum and ilium are shaped like an “inverted L”, while in females they are generally smaller and more oblique shaping a “C” appearance.17,56 Females are also generally not able to produce as much force with muscle activation compared to males. This decreased muscle output could negatively impact the “force closure” mechanism. In this mechanism the latissimus dorsi works with the contralateral gluteus maximus to generate the force closure on the SIJ as co-activation occurs and force is transferred through the posterior layer of the thoracolumbar fascia.18,19,57 The decreased amount of stability at the SIJ could explain this observed difference in injury occurrence between sexes. Position on the team also had an influence on SIJ injury. The five with an SIJ injury, two were backfield players, and three were midfielders. This is in agreement with current literature as midfielders have been reported to be at the highest rate of LBP potentially caused by an SIJ injury.10 This could be due in part that midfielders cover the most distance throughout the 19 game.58 Upon movement, roles are switched between attacking and defending. This involves increased use of the hip adductors and abductors which may lead to an inflare or outflare of the innominates59 This may result in a compression of the SIJ and a decrease of mobility in the joint. An inflare or an outflare could be potential mechanisms for the creation of pain and dysfunction at the SIJ. It has been postulated that the number of years playing soccer may have an influence on developing an SIJ injury.60 Of the five with an SIJ injury, four currently play soccer year-round and all five remain physically active. These five subjects have also been playing soccer for 8, 11, 11, 14, and 15 years, respectively. The average number of years playing soccer amongst all subjects was 9.70 years. Although no statistically significant correlations were found between years playing, current physical activity, and SIJ injury, the potential for an SIJ injury exists via a chronic/overuse mechanism. Although current research is limited on the relationship between early sports specialization and overuse injury, especially with the low back, initial findings indicate that playing a sport for 8 months or greater over the year leads to an increased risk of overuse lower extremity injuries.61-63 When injuries were reported by type, low back overuse injuries in sport specialized athletes were 13.7% in relation to all the overuse injuries reported.60 Although the research is limited, currently there is a modest relationship showing that playing a sport year-round may increase risk of an overuse injury such as SIJ. Correlation of Hip Abduction to SIJ Injury Occurrence Hip abduction is a component of multiple functional movements of soccer and this may be contributing to SIJ injury as the results from this study found a positive large correlation between the two. The fundamental skills of soccer are the kick and running involving lateral 20 movement. Hip abduction occurs during the kicking motion and lateral movements, and contribute to the “force closure” mechanism.16,18,19 More specifically, during the backswing of the kicking motion, the hip is slowly abducted and externally rotated by a concentric contraction of the gluteus medius.64 The hip remains abducted and externally rotated during the initiation of forward motion through impact with the ball.64 Meanwhile the gluteus medius on the stance leg is activated to maintain hip stabilization during the kicking motion. The gluteus medius plays an important role in the kicking motion working both as a joint mover and as a stabilizer. With the repetitive kicking motions in soccer this muscle can be quick to fatigue. Soccer players also incorporate forward, backward, and lateral motions moving up and down the field. The sacral motions become increasingly complex during the gait cycle. In walking from heel strike to midfoot stance, and toe off the sacrum goes through rotational movement in both directions as well as side bending.65 These motions and the forces transferred through the SIJ are exacerbated during running. Stress at the SIJ is further increased from the lateral movements involved with cutting in soccer. Therefore, excessive and repetitive hip abduction may result in the gluteus medius decreasing the ability to maintain stabilization of the pelvis and the SIJ, altering the biomechanics and decreasing the effectiveness of the “force closure” mechanism. The decreased stability, created by excessive and repetitive hip abduction, at the SIJ will result in increased shear forces which leads to potential injury.17,65 68 Correlations of HROM to AKET and PALM Hamstring flexibility influences both the performance of active hip flexion and the AKET. The positive medium strength correlation from this study supported that. All subjects were able to bilaterally score a three on the active straight leg test suggesting that each subject 21 has good hamstring flexibility. This is further supported by the subjects exceeding the normative values for both active hip flexion and the AKET. The hamstrings muscles collectively are a two joint muscle as they act upon both the knee and hip joint.17 During active hip flexion the proximal portion at the ischial tuberosity is put under increased strain, whereas, during the AKET the distal portion at the knee is put under increased strain.17,41,57 A subject with increased hamstring flexibility performed well in both screening variables. Active hip extension and pelvic positioning produced a positive large correlation in this study. All of the subjects were recorded to have an anterior pelvic tilt that ranged from 2.25˚ to 18.25˚. This relationship may not be due to the strength of the gluteus maximus. Perhaps this relationship can be explained with soccer specific biomechanics. The hip flexors, such as the iliopsoas and the rectus femoris, undergo eccentric contraction in the back swing followed by a powerful concentric contraction for the remaining portions of the kicking motion.69,70 This load from the hip flexors pulls on the pelvic innominates anteriorly. Additionally, an overused iliopsoas muscle may increase lumbar lordosis and inhibit transverse abdominis activation. An increased lumbar lordosis in turn creates an increased anterior pelvic tilt.71,72 The anterior pelvic tilt, altered the biomechanical positioning of the subjects’ pelvis. This altered positioning may have allowed compensation from other muscles, such as the hamstrings, to produce more force leading to increased performance in active hip extension.18,20 Model of Predicting SIJ Injury The best fit model for predicting SIJ injury was hip abduction. The odds ratio that was produced interpreted that those with the highest angle of hip abduction were at a 11.5% increased risk for SIJ injury. This contradicts current literature that has found that a decrease, rather than an increase in hip abduction is related to having an SIJ injury.22,23 It is also reported in the literature 22 that decreases in hip extension, adduction, internal rotation, and external rotation are related to an SIJ injury.21,73 Although this information conflicts with current literature, the importance of hip range of motion should be addressed, especially if asymmetry is evident in the lumbopelvic region.74 Why an increase in hip abduction may be a concern is related to the biomechanical alteration that occurs at the sacrum during kicking, running, and lateral movements in soccer. The increase in hip abduction also may influence the “force closure” mechanism that is predominantly controlled by the latissimus dorsi, gluteus maximus, and thoracolumbar fascia.16 19,57 If the sacrum cannot properly serve as the gateway between the lower extremities and the spinal column, then the forces will remain in the SIJ and result in injury. This adaptation of excessive and repetitive active hip abduction was most likely acquired over time by the subjects in this study based off the physical demands of soccer and the longevity and frequency that they have played and trained. The other models that may have some relevancy for predicting an SIJ injury included the FMS, and years playing as screening variables. Each of these models were not statistically significant, however, each was able to accurately predict one case of a SIJ injury creating potential clinical relevancy. The FMS model produced an odds ratio interpreted as a higher composite score would decrease the risk of an SIJ injury by 50.5%. This odds ratio supported the concept that clinicians frequently use the FMS as a screening tool for injury risk, despite not being the original intent of the FMS. This interpretation of the FMS has been heavily investigated and the results show that athletes who score 14 or less points on the FMS are at an increased risk for injury.34-39,75 Specifically it has been cited that a score of 14 or less on the FMS resulted in a 4-fold increase of lower extremity risk of injury over the course of a season.34 23 Observed from this binary logistic regression model it accurately predicted SIJ injury for the subject who had the lowest score, 15, of all 20 subjects who volunteered. Conversely, the other four who sustained an SIJ injury performed well with scores of 18, 18, 19, and 19, respectively. Those scores align closer to the average FMS composite score for the non-injury group (18.6 ± 0.83). Overall the group performed well with an average FMS composite score of 18.4 ± 1.10, suggesting that the athletes in this population were highly trained and capable of performing efficient athletic movements. The model for years playing soccer produced an odds ratio, which was interpreted as those with the greatest amount of years played had an increased risk of SIJ injury by 31.9%. The subjects in this group had a mean of 9.70 ± 4.05 years of soccer experience with a mean age of 16.10 ± 1.17 years. Half of these subjects’ lives have been dedicated to playing soccer. Further, there is a clinical difference in years playing soccer between the SIJ injury and healthy group. The SIJ injury group had a mean of 11.80 ± 2.77 years of playing soccer, compared to 9.00 ± 4.24 years in the healthy group. Among the five with the injury, all have been playing for 8, 11, 11, 14, and 15 years, respectively. The model accurately predicted the subject who had played for 15 years. Additionally, the subject who had 14 years of experience is the same subject with a composite score of 15 whom was accurately predicted in the FMS model. Despite limited research available on years playing on the risk of developing an overuse injury, initial findings may support the clinical relevancy of this model as there is a modest relationship between playing year-round and sustaining an overuse injury in the lower extremity.60-63 Upon investigation of a stepwise binary logistic regression, a statistically significant model including both hip abduction, and the FMS together was produced. The odds ratio when the FMS was included increased from 11.5% to a 16.8% risk of SIJ injury. This odds ratio may 24 be low; however, it holds clinical significance. The increased risk of injury suggested that these two screening variables are related to each other. The seven fundamental movements of the FMS are primarily performed in the sagittal plane; however, the subject must be able to maintain stability to not deviate into the frontal or transverse plane. This stability is controlled partly by the gluteus medius, which is the main contributor to hip abduction. The need to activate the gluteus medius during certain functional movements may be why the model’s ability to predict an SIJ injury improved with the inclusion of the FMS. The more applicable movements for soccer in the FMS are those performed in standing, including the deep squat, hurdle step, and inline lunge. Only one study has reported individual scores of the seven fundamental movements in those with chronic LBP.13 A decrease in performance for the deep squat and hurdle step were found in that study.13 Upon investigation of the individual scores from the subject who was accurately predicted by the model, the subject had decreased scores in the deep squat, hurdle step, inline lunge, trunk stability push up, and rotary stability. These decreased scores directly supported the findings of Ko et al.13 that the deep squat, hurdle step, and inline lunge are applicable to soccer. The other four subjects with SIJ injury also support the findings of Ko et al.13 The first subject had decreased performance on the deep squat and hurdle step, the second and third subjects had decreased performance on the inline lunge, and the fourth subject had decreased performance on the hurdle step. These four subjects also performed poorly on the rotary stability, however, performed well on the three remaining movements. When compared to the subjects without a SIJ injury they too produced mixed results with the deep squat and hurdle step, which may suggest an altered biomechanical pattern in soccer players exists. The subjects without a SIJ injury performed very well on the inline lunge, whereas the SIJ injury group had mixed results. This may suggest that those with an SIJ injury have poor hip stability which may 25 explain their poor performance with the inline lunge. This model may be a link to predict an SIJ injury, along with excessive hip abduction that may be caused by a dysfunctional gluteus medius and may explain decreased performance in the FMS. Clinical Importance This is the first screening tool model created for predicting an SIJ injury within this athletic population. Clinicians may use the information created by these models to develop a preseason screening tool. Two models in this study indicated a good fit for prediction which may develop a potential clinical prediction rule for clinicians to utilize active hip range of motion and the FMS in preseason screening. The model that included active hip abduction produced an odds ratio that a clinician may interpret large hip abduction measurements increased the risk of SIJ injury by 11.5%. Therefore, clinicians should be conscious of hip range of motion abnormalities in active athletic populations. In soccer, it is necessary for the hip to have six degrees of freedom to efficiently perform the running and kicking biomechanics of the sport. These motions at the hip interact in concert with motions occurring at the pelvis, sacrum, and SIJ. If one of the components has dysfunction this may transfer up the kinetic chain and create SIJD, therefore assessing hip range of motion is a necessary component to consider for a SIJD screening tool in soccer athletes. For this reason, all hip range of motion measurements, and not only hip abduction, should be included in a prediction model. When the model included the FMS with hip abduction, the odds ratio improved and was interpreted that large active hip abduction angle measurements, with low FMS composite scores resulted in a 16.8% increased risk of SIJ injury. For clinicians this shows relev