Hip Biomechanics During a Single-Leg Squat: 5 Key Differences Between People With Femoroacetabular Impingement Syndrome and Those Without Hip Pain

Synthetic data generation in motion analysis: A generative deep learning framework

Generative deep learning has emerged as a promising data augmentation technique in recent years. This approach becomes particularly valuable in areas such as motion analysis, where it is challenging to collect substantial amounts of data. The objective of the current study is to introduce a data augmentation strategy that relies on a variational autoencoder to generate synthetic data of kinetic and kinematic variables. The kinematic and kinetic variables consist of hip and knee joint angles and moments, respectively, in both sagittal and frontal plane, and ground reaction forces. Statistical parametric mapping (SPM) did not detect significant differences between real and synthetic data for each of the biomechanical variables considered. To further evaluate the effectiveness of this approach, a long-short term model (LSTM) was trained both only on real data (R) and on the combination of real and synthetic data (R&S); the performance of each of these two trained models was then assessed on real test data unseen during training. The principal findings included achieving comparable results in terms of nRMSE when predicting knee joint moments in the frontal (R&S: 9.86% vs R: 10.72%) and sagittal plane (R&S: 9.21% vs R: 9.75%), and hip joint moments in the frontal (R&S: 16.93% vs R: 16.79%) and sagittal plane (R&S: 13.29% vs R: 14.60%). The main novelty of this study lies in introducing an effective data augmentation approach in motion analysis settings.

Strength, mobility, and functional outcomes 2.5 months after hip arthroscopy for femoroacetabular impingement syndrome: A Cross-sectional Study

OBJECTIVE

Short-term deficits after hip arthroscopy for femoroacetabular impingement syndrome (FAIS) remain poorly understood. We assessed muscle strength, hip range of motion, and functional task performance 2.5 months after surgery and analyzed their association with self-reported function.

DESIGN

Cross sectional study.

PARTICIPANTS

52 patients.

MAIN OUTCOME MEASURES

Maximal isometric strength (hip flexion with both straight and flexed hip/knee, abduction and external rotation), hip range of motion (flexion, external and internal rotation), and functional tasks (bipodal/unipodal squat, bilateral vertical jump, single-leg distance hop). Between-limb differences were analyzed using paired t-tests, and the Limb Symmetry Index (LSI) was calculated.

RESULTS

The operated hip showed lower hip flexion strength (LSI = 88.4%; ES = -0.549; p < 0.001) and reduced range of motion (LSI = 75.4-92.4%; ES = -0.479 to -1.02; all p < 0.01) compared to the non-operated hip. Functional task performance did not differ between operated and non-operated hips (all p > 0.05).

CONCLUSION

Patients showed alterations in hip flexion strength and range of motion post-surgery, but functional task performance was unaffected. Targeted assessment and intervention may be needed to improve outcomes after surgery for FAIS.

Hip joint contact forces are lower in people with femoroacetabular impingement syndrome during squat tasks

It remains unknown if hip joint forces during squat tasks are altered in people with femoroacetabular impingement syndrome (FAIS). The aim of this study is to compare hip joint forces between people with FAIS and healthy controls during double leg squat and single leg squat tasks and within limbs during a single leg squat task in people with FAIS. Kinematic and kinetic data were collected in eight people with FAIS and eight healthy matched controls using 3D motion capture and force plates. AnyBody Modeling System was used to perform musculoskeletal simulations to estimate hip joint angles, forces, and moments for all participants. Estimates were postprocessed with AnyPyTools and converted into normalized time series to be compared using a 1D statistical nonparametric mapping (SnPM) approach. SnPM with an independent samples t-test model was used to compare people with FAIS to controls, while a paired samples model was used to compare involved to uninvolved limb in people with FAIS. Patients demonstrated lower proximodistal force compared to controls (p < 0.01) and compared to the uninvolved side (p = 0.01) for single leg squat. The smaller joint contact forces in people with FAIS compared to controls could represent a strategy of reduced muscle forces to avoid pain and symptoms during this high demand task. These findings when combined with imaging data could help assess the severity of FAIS on hip related function during higher demand tasks.

Comparison Between Movement Pattern Training and Strengthening on Kinematics and Kinetics in Patients With Chronic Hip-Related Groin Pain

The purpose of this study was to compare the preliminary effects of movement pattern training (MoveTrain) versus strengthening/flexibility (standard) treatment on hip and pelvic biomechanics in patients with chronic hip-related groin pain. This is a secondary analysis of data collected during a pilot randomized clinical trial. Thirty patients with hip pain, between the ages of 15 and 40 years, were randomized to MoveTrain or standard. Both groups completed 10 treatment sessions over 12 weeks along with a daily home exercise program. Three-dimensional motion analysis was used to collect kinematic and kinetic data of the pelvis and hip during a single-leg squat task at pretreatment and immediately posttreatment. Compared with the standard group, the MoveTrain group demonstrated smaller hip adduction angles (P = .006) and smaller hip external adduction moments (P = .008) at posttreatment. The desired changes to hip joint biomechanics, as found in this study, may require specificity in training that could allow health care professionals to better customize the rehabilitation of patients with hip pain. These findings can also be applied to the design and implementation of future clinical trials to strengthen our understanding of the long-term implications of different rehabilitation techniques for patients with hip pain.

Machine learning-based prediction of hip joint moment in healthy subjects, patients and post-operative subjects

The application of machine learning in the field of motion capture research is growing rapidly. The purpose of the study is to implement a long-short term memory (LSTM) model able to predict sagittal plane hip joint moment (HJM) across three distinct cohorts (healthy controls, patients and post-operative patients) starting from 3D motion capture and force data. Statistical parametric mapping with paired samples t-test was performed to compare machine learning and inverse dynamics HJM predicted values, with the latter used as gold standard. The results demonstrated favorable model performance on each of the three cohorts, showcasing its ability to successfully generalize predictions across diverse cohorts.

Hip and Pelvis Movement Patterns in Patients With Femoroacetabular Impingement Syndrome Differ From Controls and Change After Hip Arthroscopy During a Step-Down Pivot-Turn Task

Background

Alterations in hip kinematics during functional tasks occur in positions that cause anterior impingement in patients with femoroacetabular impingement (FAI) syndrome. However, tasks that do not promote motions of symptomatic hip impingement remain understudied.

Purpose

To compare movement patterns of the hip and pelvis during a step-down pivot-turn task between patients with FAI and controls as well as in patients with FAI before and after hip arthroscopy.

Study Design

Controlled laboratory study.

Methods

Three-dimensional motion capture was acquired in 32 patients with FAI and 27 controls during a step-down pivot-turn task. An FAI subsample (n = 14) completed testing 9.2 ± 2.0 months (mean ± SD; range, 5.8-13.1 months) after hip arthroscopy. Statistical parametric mapping analysis was used to analyze hip and pelvis time series waveforms (1) between the FAI and control groups, (2) in the FAI group before versus after hip arthroscopy, and (3) in the FAI group after hip arthroscopy versus the control group. Continuous parametric variables were analyzed by paired t test and nonparametric variables by chi-square test.

Results

There were no significant differences in demographics between the FAI and control groups. Before hip arthroscopy, patients with FAI demonstrated reduced hip flexion (P = .041) and external rotation (P = .027), as well as decreased anterior pelvic tilt (P = .049) and forward rotation (P = .043), when compared with controls. After hip arthroscopy, patients demonstrated greater hip flexion (P < .001) and external rotation of the operative hip (P < .001), in addition to increased anterior pelvic tilt (P≤ .036) and pelvic rise (P≤ .049), as compared with preoperative values. Postoperatively, the FAI group demonstrated greater hip flexion (P≤ .047) and lower forward pelvic rotation (P = .003) as compared with the control group.

Conclusion

Movement pattern differences between the FAI and control groups during the nonimpingement-related step-down pivot-turn task were characterized by differences in the sagittal and transverse planes of the hip and pelvis. After hip arthroscopy, patients exhibited greater hip flexion and external rotation and increased pelvic anterior tilt and pelvic rise as compared with presurgery. When compared with controls, patients with FAI demonstrated greater hip flexion and lower pelvic forward rotation postoperatively.

Clinical Relevance

These findings indicate that hip and pelvis biomechanics are altered even during tasks that do not reproduce the anterior impingement position.

Association of Changes in Hip and Knee Kinematics During a Single-Leg Squat With Changes in Patient-Reported Outcomes at 6 Months and 1 Year After Hip Arthroscopy

BACKGROUND

Previous studies have demonstrated alterations in squat kinematics in patients with femoroacetabular impingement syndrome (FAIS). Little is known about the effects of arthroscopic hip surgery on biomechanics during a single-leg squat (SLS) in these patients.

PURPOSE/HYPOTHESIS

The purpose of this study was to determine if (1) lower extremity dynamic range of motion (ROM) during an SLS task improves after hip arthroscopy for FAIS and (2) correlations exist between changes in patient-reported outcomes (PROs) and changes in lower extremity dynamic ROM during an SLS after hip arthroscopy for FAIS. It was hypothesized that dynamic hip ROM would improve after hip arthroscopy and that hip dynamic ROM would be associated with changes in PRO scores at both 6 months and 1 year.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Patients with FAIS performed 3 SLSs that were analyzed using a 20-camera motion capture system. Dynamic ROMs were calculated in 3 planes for the hip, knee, ankle, and pelvic segments. Squat depth was calculated as the change in vertical center of mass during the squat cycle. PROs including the Hip Outcome Score-Activities of Daily Living (HOS-ADL), Hip Outcome Score-Sports (HOS-Sports), International Hip Outcome Tool-12, and visual analog scale for pain scores were collected preoperatively and at the time of postoperative testing. Paired-samples t tests were used to compare kinematic variables pre- and postoperatively. Correlations were used to compare changes in PROs with changes in kinematics. All statistical analysis was performed using SPSS Version 26.

RESULTS

Fifteen patients were tested preoperatively and at a mean of 9 months postoperatively. All PRO measures improved postoperatively at 6 months and 1 year. Squat depth and sagittal plane hip and knee dynamic ROMs were significantly improved postoperatively. Positive correlations existed between changes in (1) hip ROM with the 6-month HOS-ADL score (r = 0.665) and (2) knee ROM with the 6 month (r = 0.590) and 1-year (r = 0.565) HOS-Sports scores.

CONCLUSION

Dynamic sagittal plane hip and knee ROMs improve after hip arthroscopy for FAIS. These improvements demonstrate strong correlations with improvements in some but not all postoperative PROs.

CLINICAL RELEVANCE

The current study sought to better understand the role of dynamic movement in the diagnosis and treatment of FAIS. These findings indicate that dynamic ROM and squat depth can, similarly to PROs, serve as biomarkers for patient function both before and after hip arthroscopic surgery.

Does response to preoperative intra-articular anesthetic injections predict outcomes of femoroacetabular impingement syndrome?

INTRODUCTION

Some patients with femoroacetabular impingement syndrome (FAIS) who undergo surgery do not show satisfactory outcomes. Reliable tests that can inform prognosis of FAIS surgery are needed for optimized indications and contraindications to surgery. We aimed to review and critically appraise available literature on the capability of patient response to preoperative intra-articular anesthetic injections (PIAI) to predict post-surgical outcomes in patients with FAIS.

MATERIALS AND METHODS

This study was conducted in accordance with the PRISMA statement. Studies that assessed the patient pain response to PIAI and post-surgical outcomes in patients with FAIS were considered eligible. Study selection and data collection were performed by three independent reviewers. Main outcomes evaluated were those measured by hip outcome scales often used in assessing postoperative pain and functional recovery, such as the modified Harris Hip Score (mHHS) and international Hip Outcome Tool (iHOT). The likelihood ratio of achieving satisfactory postoperative outcomes at the mHHS (LHR) was extracted or calculated-for patients with significant response to PIAI and for those without a significant response to PIAI. The risk of bias was assessed using the Quality In Prognosis Studies (QUIPS) tool.

RESULTS

Six studies were considered eligible for analysis. Five studies indicated that patient response to PIAI are associated to surgical outcomes for patients with FAIS, with a greater reduction in pain typically indicating a better surgical outcome. Additionally, the LHR ranged from 1.15 to 1.92 for patients with significant response to PIAI (I2 = 90.6%). For patients without a significant response, the LHR ranged from 0.18 to 0.65 (I2 = 87.5). An overall high risk of bias was observed for all studies included in the analysis. Study attrition, the prognostic factor measurement and the presence of confounding factors were the main sources of bias.

CONCLUSIONS

Greater reductions in pain with preoperative intra-articular anesthetic injections were found to be associated to better outcomes after FAIS surgery, but all available studies contain a high risk of bias.

Running Mechanics After Repeated Sprints in Femoroacetabular Impingement Syndrome, Cam Morphology, and Controls

BACKGROUND

People with femoroacetabular with femoroacetabular impingement syndrome (FAIS) often report pain during sports involving repeated sprinting. It remains unclear how sports participation influences running biomechanics in individuals with FAIS.

HYPOTHESIS

Changes in running biomechanics and/or isometric hip strength after repeated sprint exercise would be greatest in individuals with FAIS compared with asymptomatic individuals with (CAM) and without cam morphology (Control).

STUDY DESIGN

Controlled laboratory study.

LEVEL OF EVIDENCE

Level 3.

METHODS

Three-dimensional hip biomechanics during maximal running (10 m) and hip strength were measured in 49 recreationally active individuals (FAIS = 15; CAM = 16; Control = 18) before and after repeated sprint exercise performed on a nonmotorized treadmill (8-16 × 30 m). Effects of group and time were assessed for biomechanics and strength variables with repeated-measures analyses of variance. Relationships between hip pain (Copenhagen Hip and Groin Outcome Score) and changes in hip moments and strength after repeated sprint exercise were determined using Spearman's correlation coefficients (ρ).

RESULTS

Running speed, hip flexion angles, hip flexion and extension moments, and hip strength in all muscle groups were significantly reduced from pre to post. No significant between-group differences were observed before or after repeated sprint exercise. No significant relationships (ρ = 0.04-0.30) were observed between hip pain and changes in hip moments or strength in the FAIS group.

CONCLUSION

Changes in running biomechanics and strength after repeated sprint exercise did not differ between participants with FAIS and asymptomatic participants with and without cam morphology. Self-reported pain did not appear to influence biomechanics during running or strength after repeated sprint exercise in participants with FAIS.

CLINICAL RELEVANCE

A short bout of repeated sprinting may not elicit changes in running biomechanics in FAIS beyond what occurs in those without symptoms. Longer duration activities or activities requiring greater hip flexion angles may better provoke pathology-related changes in running biomechanics in people with FAIS.

Smartphone Technology to Remotely Measure Postural Sway during Double- and Single-Leg Squats in Adults with Femoroacetabular Impingement and Those with No Hip Pain

BACKGROUND

The COVID-19 pandemic has accelerated the demand for utilising telehealth as a major mode of healthcare delivery, with increasing interest in the use of tele-platforms for remote patient assessment. In this context, the use of smartphone technology to measure squat performance in people with and without femoroacetabular impingement (FAI) syndrome has not been reported yet. We developed a novel smartphone application, the TelePhysio app, which allows the clinician to remotely connect to the patient's device and measure their squat performance in real time using the smartphone inertial sensors. The aim of this study was to investigate the association and test-retest reliability of the TelePhysio app in measuring postural sway performance during a double-leg (DLS) and single-leg (SLS) squat task. In addition, the study investigated the ability of TelePhysio to detect differences in DLS and SLS performance between people with FAI and without hip pain.

METHODS

A total of 30 healthy (nfemales = 12) young adults and 10 adults (nfemales = 2) with diagnosed FAI syndrome participated in the study. Healthy participants performed DLS and SLS on force plates in our laboratory, and remotely in their homes using the TelePhysio smartphone application. Sway measurements were compared using the centre of pressure (CoP) and smartphone inertial sensor data. A total of 10 participants with FAI (nfemales = 2) performed the squat assessments remotely. Four sway measurements in each axis (x, y, and z) were computed from the TelePhysio inertial sensors: (1) average acceleration magnitude from the mean (aam), (2) root-mean-square acceleration (rms), (3) range acceleration (r), and (4) approximate entropy (apen), with lower values indicating that the movement is more regular, repetitive, and predictable. Differences in TelePhysio squat sway data were compared between DLS and SLS, and between healthy and FAI adults, using analysis of variance with significance set at 0.05.

RESULTS

The TelePhysio aam measurements on the x- and y-axes had significant large correlations with the CoP measurements (r = 0.56 and r = 0.71, respectively). The TelePhysio aam measurements demonstrated moderate to substantial between-session reliability values of 0.73 (95% CI 0.62-0.81), 0.85 (95% CI 0.79-0.91), and 0.73 (95% CI 0.62-0.82) for aamx, aamy, and aamz, respectively. The DLS of the FAI participants showed significantly lower aam and apen values in the medio-lateral direction compared to the healthy DLS, healthy SLS, and FAI SLS groups (aam = 0.13, 0.19, 0.29, and 0.29, respectively; and apen = 0.33, 0.45, 0.52, and 0.48, respectively). In the anterior-posterior direction, healthy DLS showed significantly greater aam values compared to the healthy SLS, FAI DLS, and FAI SLS groups (1.26, 0.61, 0.68, and 0.35, respectively).

CONCLUSIONS

The TelePhysio app is a valid and reliable method of measuring postural control during DLS and SLS tasks. The application is capable of distinguishing performance levels between DLS and SLS tasks, and between healthy and FAI young adults. The DLS task is sufficient to distinguish the level of performance between healthy and FAI adults. This study validates the use of smartphone technology as a tele-assessment clinical tool for remote squat assessment.

Single-Leg Squat Test in the Clinical Setting Does Not Discriminate Patients With Femoroacetabular Impingement Syndrome From Asymptomatic Individuals

CONTEXT

Laboratorial 3-dimensional kinematic analyses have shown changes in the single-leg squat's (SLS) pattern of patients with femoroacetabular impingement syndrome (FAIS). However, it is unknown whether clinicians are able to detect these changes using 2-dimensional kinematics.

OBJECTIVE

To compare the frontal plane 2-dimensional kinematics of patients with FAIS and asymptomatic individuals in the SLS test performed in a clinical setting.

DESIGN

Case-control study.

SETTING

Physical therapy clinic.

PARTICIPANTS

Twenty men with bilateral FAIS and 20 asymptomatic men.

MAIN OUTCOME MEASURES

Two-dimensional kinematic analysis was collected in the frontal plane during the execution of the SLS test. The outcomes were squat depth, pelvic drop (pelvis angle relative to the horizontal plane), hip adduction (femur angle relative to the pelvis), and knee valgus (femur angle relative to the tibia).

RESULTS

Most and least painful limbs of patients with FAIS had squat depth (9.8% [2.9%] and 9.5% [3.1%] of height), pelvic drop (4.2° [3.9°] and 3.7° [4.2°]), hip adduction (74.9° [5.8°] and 75.9° [5.7°]), and knee valgus (4.0° [11.0°] and 5.0° [9.9°]) similar to asymptomatic individuals (9.0% [2.3%], 4.8° [2.6°], 73.7° [4.9°], and -1.7° [8.5°]; P > .05 for all).

CONCLUSION

The frontal plane 2-dimensional kinematic analysis of the SLS test in the clinical setting is not able to distinguish patients with FAIS from asymptomatic individuals.

Gluteal activation during squatting reduces acetabular contact pressure in persons with femoroacetabular impingement syndrome: A patient-specific finite element analysis

BACKGROUND

Femoroacetabular impingement syndrome is a motion-related clinical disorder resulting from abnormal hip joint morphology. Mechanical impingement, in which the aspherical femoral head (cam morphology) abuts with the acetabular rim, is created with simultaneous hip flexion, internal rotation, and adduction. Impaired function of the gluteal muscles may be contributory to femoroacetabular impingement syndrome progression. The purpose of this study was to assess the influence of gluteal muscle recruitment on acetabular contact pressure during squatting in persons with cam femoroacetabular impingement syndrome.

METHODS

Eight individuals (4 males, 4 females) with a diagnosis of cam femoroacetabular impingement syndrome underwent CT imaging of the pelvis and proximal femora, and a biomechanical assessment of squatting (kinematics, kinetics, and electromyography). Two maximal depth bodyweight squat conditions were evaluated: 1) non-cued squatting; and 2) cued gluteal activation squatting. Utilizing subject-specific electromyography-driven hip and finite element modeling approaches, hip muscle activation, kinematics, bone-on-bone contact forces, and peak acetabular contact pressure were compared between squat conditions.

FINDINGS

Modest increases in gluteus maximus (7% MVIC, P < 0.0001) and medius (6% MVIC, P = 0.009) activation were able to reduce hip internal rotation on average 5° (P = 0.024), and in doing so reduced acetabular contact pressure by 32% (P = 0.023). Reductions in acetabular contact pressure occurred despite no change in hip abduction and increased bone-on-bone contact forces occurring in the cued gluteal activation condition.

INTERPRETATION

Our findings highlight the importance of gluteal activation in minimizing mechanical impingement and provide a foundation for interventions aimed at preventing the development and progression of femoroacetabular impingement syndrome.

Influence of Loads and Loading Position on the Muscle Activity of the Trunk and Lower Extremity during Squat Exercise

This study aimed to investigate the effect of the load and bar position on trunk and lower extremity muscle activity during squat exercise. High bar back squats (HBBS) and low bar back squats (LBBS) were performed in random order at 50%, 60%, and 70% loads of one repetition maximum by 28 experienced healthy adult men who had been performing squats for at least one year. Before the experiment, the maximal voluntary contraction of the vastus medialis, vastus lateralis, rectus femoris, biceps femoris, rectus abdominis, transverse abdominis, external oblique, and erector spinae muscles was measured by means of surface electromyography. In addition, eccentric and concentric exercises were performed for 3 s each to measure the muscle activity. There was a significant difference in muscle activity according to the load for all muscles in the eccentric and concentric phases (p < 0.05), indicating that muscle activity increased as the load increased. In addition, in the comparison between HBBS and LBBS, significant differences were shown in all lower extremity muscles and all trunk muscles except for the external oblique in the concentric phase according to the bar position (p < 0.05). HBBS showed a higher muscle activity of the lower extremity in the eccentric and concentric phases than in LBBS, while LBBS showed a higher muscle activity of the trunk muscle in the eccentric and concentric phases than in HBBS (p < 0.05). HBBS requires more force in the lower extremity than LBBS and is particularly advantageous in strengthening the muscular strength of the quadriceps. In contrast, LBBS requires more muscle activity in the trunk than HBBS and is more effective in carrying heavier loads because of the advantage of body stability. This study suggests that rehabilitation experts apply the bar position and load as important variables affecting the intensity and method of training for target muscle strengthening of the lower extremities and trunk.

Electromyography measurements of the deep hip muscles do not improve estimates of hip contact force

The deep hip muscles are often omitted in studies investigating hip contact forces using neuromusculoskeletal modelling methods. However, recent evidence indicates the deep hip muscles have potential to change the direction of hip contact force and could have relevance for hip contact loading estimates. Further, it is not known whether deep hip muscle excitation patterns can be accurately estimated using neuromusculoskeletal modelling or require measurement (through invasive and time-consuming methods) to inform models used to estimate hip contact forces. We calculated hip contact forces during walking, squatting, and squat-jumping for 17 participants using electromyography (EMG)-informed neuromusculoskeletal modelling with (informed) and without (synthesized) intramuscular EMG for the deep hip muscles (piriformis, obturator internus, quadratus femoris). Hip contact force magnitude and direction, calculated as the angle between hip contact force and vector from femoral head to acetabular center, were compared between configurations using a paired t-test deployed through statistical parametric mapping (P < 0.05). Additionally, root mean square error, correlation coefficients (R²), and timing accuracy between measured and modelled deep hip muscle excitation patterns were computed. No significant between-configuration differences in hip contact force magnitude or direction were found for any task. However, the synthesized method poorly predicted (R²-range 0.02-0.3) deep hip muscle excitation patterns for all tasks. Consequently, intramuscular EMG of the deep hip muscles may be unnecessary when estimating hip contact force magnitude or direction using EMG-informed neuromusculoskeletal modelling, though is likely essential for investigations of deep hip muscle function.

Neuromuscular Consequences of Lumbopelvic Dysfunction: Research and Clinical Perspectives

Injuries involving the lumbopelvic region (ie, lumbar spine, pelvis, hip) are common across the lifespan and include pathologies such as low back pain, femoroacetabular impingement syndrome, labrum tear, and osteoarthritis. Joint injury is known to result in an arthrogenic muscle response which contributes to muscle weakness and altered movement patterns. The purpose of this manuscript is to summarize the arthrogenic muscle response that occurs across lumbopelvic region pathologies, identify methods to quantify muscle function, and propose suggestions for future research. While each lumbopelvic region pathology is unique, there are a few common impairments and a relative consistent arthrogenic muscle response that occurs across the region. Hip muscle weakness and hip joint range of motion limitations occur with both lumbar spine and hip pathologies, and individuals with low back pain are known to demonstrate inhibition of the transversus abdominis and multifidus. Assessment of muscle inhibition is often limited to research laboratory settings, but dynamometers, ultrasound imaging, and electromyography offer clinical capacity to quantify muscle function and inform treatment pathways. Future studies should systematically determine the arthrogenic muscle response across multiple muscle groups and the timeline for changes in muscle function and determine whether disinhibitory modalities improve functional outcomes beyond traditional treatment approaches.

Balancing Act: Muscle Imbalance Effects on Musculoskeletal Injuries

Overuse injuries affect persons of all ages and physical participation levels. These injuries involve repetitive overload causing damage and pain to various joints, affecting performance and ability to continue participation. Even when an injury diagnosis is apparent, functional assessment is useful in discovering the underlying mechanism.

Physical Examination of the Hip: Assessment of Femoroacetabular Impingement, Labral Pathology, and Microinstability

Purpose of Review

Determining the correct diagnosis can be challenging in patients presenting with hip pain. The physical examination is an essential tool that can aid in diagnosis of hip pathology. The purpose of this review is to provide an updated summary of recent literature on the physical exam of the hip, particularly as it relates to diagnosis of femoroacetabular impingement (FAI) syndrome, labral injury, and hip microinstability.

Recent Findings

Physical exam findings consistent with the diagnosis of FAI include reduced supine hip internal rotation and positive flexion-adduction-internal rotation maneuvers. Labral tears can be detected on exam with the Scour test. Studies demonstrate altered hip biomechanics in patients with FAI during activities such as walking and squatting. Those with FAI have slower squat velocities, slower sit-to-stand tests, and increased hip flexion moments during ambulation. Hip microinstability is a dynamic process, which can occur after prior hip arthroscopy. For hip microinstability, the combination of the three following positive tests (anterior apprehension, abduction-extension-external rotation, and prone external rotation) is associated with a 95% likelihood of microinstability as confirmed by examination under anesthesia at the time of surgery.

Summary

A comprehensive hip physical exam involves evaluation of the hip in multiple positions and assessing hip range of motion, strength, as well as performing provocative testing. A combination of physical exam maneuvers is necessary to accurately diagnose FAI syndrome and labral pathology as individual tests vary in their sensitivity and specificity. While an elevated level of suspicion is needed to diagnose hip microinstability, the provocative tests for microinstability are highly specific.

Dynamic Assessment of Femoroacetabular Impingement Syndrome Hips

PURPOSE

The purpose of our study was to compare lower extremity rotational kinematics and kinetics (angles, torques, and powers) and hip muscle electromyography (EMG) activity between cam-type femoroacetabular impingement syndrome (FAIS) and age- and sex-matched controls during walking, fast walking, stair ascent, stair descent, and sit-to-stand.

METHODS

This study included 10 males with unilateral FAIS and 10 control males with no FAIS. We measured kinematics, kinetics, and electromyographic signals during stair ascent/descent, sit-to-stand, self-selected walk, and fast walk. Peak signal differences between groups were compared with independent t-tests with statistical significance when P < .05.

RESULTS

FAIS hips showed significant differences compared to controls, including increased hip flexion during walking (+4.9°, P = .048) and stair ascent (+7.8°, P =.003); diminished trunk rotation during stair ascent (-3.4°; P = .015), increased knee flexion during self-selected walking (+5.1°, P = .009), stair ascent (+7.4°, P = .001), and descent (+5.3°, P = .038); and increased knee valgus during fast walking (+4.7°, P = .038). gMed and MedHam showed significantly decreased activation in FAIS during walking (gMed: -12.9%, P = .002; MedHam: -7.4%, P = .028) and stair ascent (gMed: -16.7%, P = .036; MedHam: -13.0%, P = .041); decreased gMed activation during sit-to-stand (-8.8%, P = .004) and decreased MedHam activation during stair descent (-8.0%, P = .039).

CONCLUSIONS

Three-dimensional motion analysis and EMG evaluation of functional kinematics and kinetics in subjects with symptomatic unilateral cam-type FAIS across a spectrum of provocative tasks demonstrated significant differences compared to controls in hip flexion, trunk rotation, knee flexion, and valgus. FAIS hips had significantly decreased gMed and MedHam activity. These findings may explain altered torso-pelvic, hip, and knee mechanics in FAIS patients and suggest that evaluation of FAIS should include the patient's hip, knee, and torso-pelvic relationships and muscle function.

CLINICAL RELEVANCE

The clinical and functional manifestation of FAIS hip pathomechanics is not entirely understood, and previous literature to date has not clearly described the alterations in gait and functional movements seen in patients with cam-type FAIS. The current study used 3D motion analysis and EMG evaluation of functional kinematics and kinetics to identify a number of differences between FAIS and control hips, which help us better understand the lower extremity kinematics and kinetics and muscle activation in FAIS.

Application of the 4-Element Movement System Model to Sports Physical Therapy Practice and Education

The 4-Element Movement System Model describes primary elements (motion, force, motor control, and energy) essential to the performance of all movements. The model provides a framework or scaffolding which allows for consistent processes to be used in examination and intervention decisions. The process starts with task identification followed by a systematic observation of control, amount, speed, symmetry, and symptoms during movement. Testable hypotheses are generated from the observations which inform the examination and the interventions. This commentary describes the use of the 4-Element Movement System Model in entry level and post-graduate residency educational programs and in clinical care with three common sports-related diagnoses.

LEVEL OF EVIDENCE

5.

Movement Patterns and Their Associations With Pain, Function, and Hip Morphology in Individuals With Femoroacetabular Impingement Syndrome: A Scoping Review

OBJECTIVE

The purpose of the study was to synthesize studies of movement patterns and their association with hip pain, function/activity, and morphology in individuals with femoroacetabular impingement syndrome (FAIS).

METHODS

PubMed, SPORTDiscus, CINAHL, Embase, and Scopus databases were searched using predefined terms. Two authors independently reviewed abstracts and full texts. Studies were included if they enrolled individuals with FAIS, reported kinematic or kinetic data during movement tasks, and tested the data's associations with hip pain, function/activity, or morphology. Exclusion criteria were studies that did not evaluate associations between movement patters and pain, function/activity, or hip morphology. Additionally, studies with hip conditions other than FAIS, case reports, conference proceedings, review articles, and non-English studies were excluded. Descriptive consolidation and qualitative synthesis were performed for the included studies.

RESULTS

Of the 1155 potential studies, 5 studies met all eligibility criteria. Movement patterns were evaluated during walking (n = 4) and squatting (n = 1). Studies reported multiple associations between variables of interest. Statistically significant associations were identified between movement patterns and hip pain (n = 2), function/activity (n = 2), or morphology (n = 3). Significant associations included increased hip flexion moment impulse during walking was associated with worse pain, increased hip flexion moment during walking was associated with worse hip function, decreased hip external rotation during gait and hip internal rotation during squat were associated with larger cam deformity, and increased hip flexion moment impulse during walking was also associated with more severe acetabular cartilage abnormalities.

CONCLUSIONS

Very little current evidence has evaluated the associations between altered movement patterns and hip pain, function/activity, or morphology in individuals with FAIS, and only low-intensity tasks have been tested. These studies found some preliminary associations between altered hip biomechanics and higher hip pain, worse hip function, and specific measures of hip morphology in individuals with FAIS.

IMPACT

This review is a first step in gaining a better understanding of movement patterns and their associations with hip pain, function/activity, and morphology, which could ultimately assist with the development of movement retraining interventions and potentially improve rehabilitation outcomes for those with FAIS.

Hip Joint Kinematic Covariation During Gait Before and 1-Year After Hip Arthroscopic Surgery for Femoroacetabular Impingement Syndrome

The primary aim of this study was to determine if the three-dimensional (3D) hip joint motion coordination during gait changes after arthroscopic surgery for femoroacetabular impingement syndrome (FAIS). Three-dimensional hip joint kinematic data were collected with a 12-camera motion capture system. Five trials of level walking were collected preoperatively (PRE) and at 1-year postoperatively (POST) in 8 patients diagnosed with FAIS and at a single time point in 8 healthy controls. Planar covariation analysis was performed to quantify the 3D hip joint motion coordination strategy during gait. Independent sample's t-test were used to determine differences between the FAIS group at the preoperative time point (PRE) and healthy controls. Paired samples t-tests were used to determine differences between the PRE and POST time points within the FAIS group. The %VAF by PC 1 for the FAIS group at the PRE time point was significantly less than that of healthy controls (PRE: 77.2 ± 8.7% vs. Control: 96.1 ± 2.8%; p = 0.0001), and the % VAF of the second PC (PC2) was significantly greater [PRE: 22.8 (8.7)%; Control: 3.9 (2.8)%; p = 0.0001]. No differences in %VAF were found between the PRE and POST time points within the FAIS group for PC1 [PRE: 77.2 (8.7)% vs. POST: 79.3 (11.1)%; p = 0.472] or PC2 [PRE: 22.7 (8.7)%; POST: 20.7 (11.1)%; p = 0.472]. Significant differences in the plane specific contribution to the 3D motion coordination strategy were found between the FAIS patients at the PRE and POST time points for the sagittal plane [PRE: 5.6 (2.7) vs. POST: 0.91 (6.1); p = 0.012] and frontal plane [PRE: −10.4 (2.2) and −1.5 (6.3); p = 0.005]. Patients with FAIS demonstrated a more complex coordination strategy of 3D hip joint motion than controls and this strategy remains unchanged after hip arthroscopic surgery despite changes in the plane specific contribution to this strategy. These findings indicate that motor control impairments in FAIS patients do exist and seem to persist for at least 1 year after hip arthroscopic surgery.

Impaired Lower Extremity Biomechanics, Hip External Rotation Muscle Weakness, and Proximal Femoral Morphology Predict Impaired Single-Leg Squat Performance in People With FAI Syndrome

BACKGROUND

Impairments in squat depth have been reported in patients with femoroacetabular impingement syndrome (FAIS). However, little is known about single-leg squat (SLS) performance in these patients, despite this task being commonly used in the rehabilitation and training settings.

PURPOSE/HYPOTHESIS

The aims of this study were (1) to investigate whether patients with FAIS demonstrate differences in SLS performance compared with healthy controls and (2) to determine whether dynamic range of motion (ROM), muscle strength, hip morphologic measures, hip pain, and hip-specific function predict SLS performance in patients with FAIS. We hypothesized that patients with FAIS would demonstrate impaired SLS performance and that impaired hip biomechanics, muscle strength, and hip-specific function would predict squat performance in patients with FAIS.

STUDY DESIGN

Controlled laboratory study.

METHODS

Three-dimensional (3D) kinematic data were collected at 100 Hz using a 20-camera 3D motion capture system during 3 SLS trials in 34 patients with FAIS and 26 healthy controls. Isometric muscle strength was tested with a stationary handheld dynamometer in all participants. Squat performance was quantified by squat depth (in meters), and the biomechanical variables of dynamic ROM of the pelvis, the hip, the knee, and the ankle in all planes were calculated. In patients with FAIS, femoral and acetabular morphology were measured using radiographic alpha angles and lateral center-edge angles. Hip pain and hip-specific function were measured using the visual analog scale for pain and the Hip Outcome Score Activities of Daily Living subscale, respectively. Two-tailed independent-samples t tests were used to determine between-group differences for squat depth, dynamic ROM variables, and muscle strength. A hierarchical multiple linear regression (MLR) model was used to determine whether biomechanical variables, muscle strength, hip morphology measures, hip pain, and hip-specific function were predictors of squat depth. All statistical analyses were performed using SPSS Version 26.

RESULTS

There were no between-group differences in age (FAIS, 30.0 ± 7.0 years vs controls, 27.3 ± 7.0 years; P = .18) or body mass index (FAIS, 23.1 ± 2.8 vs controls, 22.6 ± 3.2; P = .51). Squat depth was less in patients with FAIS compared with healthy controls (FAIS, 0.24 ± 0.4 m vs controls, 0.29 ± 0.05 m; P < .001). In the sagittal plane, patients with FAIS demonstrated less dynamic ROM of the hip (FAIS, 67.8°± 12.4° vs controls, 79.2°± 12.5°; P = .001) and the knee (FAIS, 71.9°± 9.4° vs controls, 78.9°± 13.2°; P = .02) compared with controls. Patients with FAIS also demonstrated a less dynamic coronal plane pelvis ROM (FAIS, 11.3°± 5.0° vs controls, 14.4°± 6.7°; P = .044). Patients with FAIS had reduced hip muscle strength of the hip external rotator (FAIS, 1 ± 0.3 N/kg vs controls, 1.2 ± 0.3 N/kg; P = .034), hip internal rotator (FAIS, 0.8 ± 0.3 N/kg vs controls 1 ± 0.3 N/kg; P = .03), and hip flexor (FAIS, 4 ± 1.1 N/kg vs controls, 4.8 ± 1.2 N/kg; P = .013) muscle groups. The hierarchical MLR revealed that the dynamic ROM of the hip, the knee, and the pelvis, the hip external rotation muscle strength, and the femoral alpha angles were all significant predictors of squat performance, and the final MLR model explained 92.4% of the total variance in squat depth in patients with FAIS.

CONCLUSION

Patients with FAIS demonstrate impaired SLS squat performance compared with healthy controls. This impaired squat performance is predominantly predicted by sagittal plane knee and hip biomechanics and hip external rotator strength, and less by frontal plane pelvic ROM and hip morphology in patients with FAIS.

CLINICAL RELEVANCE

Clinicians should focus treatment on improving dynamic ROM and hip external rotator muscle strength to improve squat performance; however, femoral morphology should also be considered in the treatment paradigm.

Biomechanical and clinical outcomes in response to inpatient multidisciplinary hip and groin rehabilitation in UK military personnel

INTRODUCTION

Hip and groin related pain is a common complaint among the military population across UK Defence Rehabilitation and addressing associated biomechanical dysfunction is a key treatment goal. Personnel are exposed to complex occupational loads, therefore assessing movement during demanding tasks may expose biomechanical deficits. Observing biomechanical and clinical outcomes in response to treatment is therefore an important consideration. The aims were to examine clinical and biomechanical outcomes prior to (T₁) and 12 weeks post (T₂) inpatient rehabilitation and explore the influence of pathological subgroup.

METHODS

Prospective cohort study as part of a clinical service evaluation of 25 patients undergoing treatment for hip and groin related pain. Three-dimensional motion capture (3DM) during a single-leg squat, hip strength and patient-reported outcome measures were collected at T₁ and T₂.

RESULTS

Increased abductor and external rotator strength with reductions in contralateral pelvic drop (1.9°; p=0.041) at T₂ on the injured side. Pain reduced by 9.6 mm (p=0.017) but no differences were found for Non-Arthritic Hip Score (NAHS). No statistically significant differences were found between pathological subgroups. Kinematic profiles display variation between diagnostic subgroups and response to treatment.

CONCLUSION

Strength and pain improved with treatment in this service evaluation although biomechanical adaptation and NAHS remain inconclusive. Small and uneven sample size prevents a firm conclusion regarding the effect of pathological subgroupings, however, the data can be considered hypothesis generating for future, larger studies to integrate 3DM for monitoring response to rehabilitation in pathological subgroups to support clinical decision making.

Squat and gait biomechanics 6 months following hip arthroscopy for femoroacetabular impingement syndrome

The purpose of this study was to (i) assess whether squat and gait biomechanical measures improve in patients with femoroacetabular impingement syndrome (FAIS) 6 months after surgery compared to pre-operative measures and (ii) compare biomechanical properties to controls without FAIS. In this prospective study, biomechanical data during a double leg squat task and gait for 15 FAIS patients and 9 controls were collected using three-dimensional motion analysis. Data were collected in the FAIS group at two-time points, pre-operatively and 6-month post-operatively following arthroscopic hip surgery, and at a single time point for the healthy controls. Independent sample's t-test were used to compare the FAIS group to the controls, and paired samples t-test were used to determine within-group differences before and after hip arthroscopy in the FAIS group. The results indicated that there were significant within-group increases for sagittal plane moment rate during the double leg squat task (P = 0.009) between the pre-operative and post-operative time points for the FAIS group. Between-group differences showed that FAIS patients pre-operatively exhibit slower squat velocities during the descent (P = 0.005) and ascent phase (P = 0.012) of a double leg squat when compared healthy controls. Reduced hip external rotation moments during gait (P = 0.02) were also found between FAIS patients pre-operatively and controls. In conclusion, alterations in hip biomechanics are present before surgery for FAIS when compared to healthy controls, and joint mechanics change 6 months after surgery. However, the biomechanical differences during a double leg squat and gait were minimal.