Hip muscle strength in male and female patients with femoroacetabular impingement syndrome: Comparison to healthy controls and athletes.

OBJECTIVES: To examine hip muscle strength deficits in patients with femoroacetabular impingent syndrome (FAIS), with special emphasis on potential sex- and comparison-related (between-subject vs within-subject) differences. DESIGN: Cross-sectional comparative study. PARTICIPANTS: Forty FAIS patients (20 women), 40 healthy controls (20 women) and 40 athletes (20 women). MAIN OUTCOME MEASURES: Hip abduction, adduction and flexion isometric strength was tested using a commercially-available dynamometer. Two between-subject comparisons (FAIS patients vs controls and FAIS patients vs athletes) and one within-subject comparison (inter-limb asymmetry) of strength deficits were conducted, based on the calculation of respective percent differences. RESULTS: For all hip muscle groups, women were 14-18% weaker than men (p < 0.001), but no sex-related interactions were observed. For all hip muscle groups, FAIS patients were 16-19% weaker than controls (p = 0.001) and 24-30% weaker than athletes (p < 0.001). For FAIS patients, the involved hip abductors were 8.5% weaker than the uninvolved ones (p = 0.015), while no inter-limb asymmetry was observed for the other hip muscles. CONCLUSION: Sex had no influence on hip muscle strength deficits in FAIS patients while a major impact of comparison method/group was observed. Hip abductors showed consistent deficits for all comparison methods, suggestive of a possible greater impairment compared to hip flexors and adductors.

Sex-Specific Differences in Hip Muscle Cross-sectional Area and Fatty Infiltration in Patients With Femoroacetabular Impingement Syndrome.

Background: Patients with femoroacetabular impingement syndrome (FAIS) show sex-specific differences in hip muscle function, hip morphology, and symptoms. Possible differences in hip muscle characteristics between men and women with FAIS are unknown. Purpose: To compare hip muscle cross-sectional area (CSA) and fatty infiltration between men and women with FAIS and investigate possible associations with patient-reported outcomes. Study Design: Cohort study; Level of evidence, 3. Methods: We retrospectively analyzed preoperative axial pelvic magnetic resonance imaging scans of 104 patients (54 women) who underwent hip surgery for FAIS. The main outcome measures were side-to-side percentage asymmetry in hip muscle CSA and involved-side fatty infiltration as measured with the Goutallier scale for a total of 10 hip muscles. Patient-reported outcomes included duration of hip symptoms, iHOT-12 (12-item International Hip Outcome Tool), and Hip Sports Activity Scale. Results: Women showed larger hip abductor muscle CSA asymmetry than men (P = .018), particularly for the gluteus medius (P = .049), while men exhibited more fatty streaks (grade 1) in the gluteus medius (P = .015) than women. Duration of symptoms was associated only with fatty infiltration of obturator externus in men (r S = -0.55, P = .018). iHOT-12 was associated with CSA asymmetry of the gluteus minimus (r = -0.41, P = .011) and iliopsoas (r = -0.36, P = .028) in men and with piriformis fatty infiltration (r S = -0.56, P = .030) in women. The Hip Sports Activity Scale was associated with iliopsoas CSA asymmetry (r S = 0.32, P = .026) and with fatty infiltration of the tensor fasciae latae (r S = -0.45, P = .046) and obturator externus (r S = -0.50, P = .023) in women. Conclusion: Patients with FAIS demonstrated few sex-specific quantitative and qualitative alterations of hip muscles. Women showed greater hip abductor muscle atrophy than men, particularly for the gluteus medius, while men showed a higher degree of fatty infiltration in this same muscle. The duration of hip symptoms was not associated with muscle atrophy. Patient-reported hip pain/function and sport activity level were only moderately associated with isolated muscular variables.

MME+ fibro-adipogenic progenitors are the dominant adipogenic population during fatty infiltration in human skeletal muscle.

Fatty infiltration, the ectopic deposition of adipose tissue within skeletal muscle, is mediated via the adipogenic differentiation of fibro-adipogenic progenitors (FAPs). We used single-nuclei and single-cell RNA sequencing to characterize FAP heterogeneity in patients with fatty infiltration. We identified an MME+ FAP subpopulation which, based on ex vivo characterization as well as transplantation experiments, exhibits high adipogenic potential. MME+ FAPs are characterized by low activity of WNT, known to control adipogenic commitment, and are refractory to the inhibitory role of WNT activators. Using preclinical models for muscle damage versus fatty infiltration, we show that many MME+ FAPs undergo apoptosis during muscle regeneration and differentiate into adipocytes under pathological conditions, leading to a reduction in their abundance. Finally, we utilized the varying fat infiltration levels in human hip muscles and found less MME+ FAPs in fatty infiltrated human muscle. Altogether, we have identified the dominant adipogenic FAP subpopulation in skeletal muscle.

Mid-term outcomes of exercise therapy for the non-surgical management of femoroacetabular impingement syndrome: are short-term effects persisting?

OBJECTIVES: To investigate the mid-term outcomes of exercise therapy in patients with femoroacetabular impingement syndrome (FAIS). DESIGN: Follow-up study. SETTING: Clinical setting. PARTICIPANTS: Twenty-six patients with FAIS who completed a 12-week semi-standardized, progressive exercise therapy program. MAIN OUTCOME MEASURES: At a mid-term follow-up of 4.6 years, therapy outcome was assessed using (i) the Global Treatment Outcome questionnaire for hip pain, (ii) the Hip Outcome Score (HOS) for hip pain and function in activities of daily living (ADL) and Sport and (iii) the Hip Sports Activity Scale (HSAS) for sport activity level. Mid-term outcomes were compared to pre-symptomatic, pre-therapy, as well as to short-term follow ups (18 weeks). RESULTS: In patients who completed the exercise program and did not undergo hip surgery (N = 19), mid-term HOS ADL and HOS Sport (P = 0.002) were higher than pre-therapy, and comparable to the 18-week follow-up. Mid-term HSAS was lower than the pre-symptomatic status (P = 0.022), but comparable to the 18-week follow-up. CONCLUSION: At a mid-term follow-up of 4.6 years, FAIS patients with no subsequent hip surgery maintained the good exercise therapy outcomes and the level of sport activity achieved at short term.

Subject-Specific Modeling of Femoral Torsion Influences the Prediction of Hip Loading During Gait in Asymptomatic Adults.

Hip osteoarthritis may be caused by increased or abnormal intra-articular forces, which are known to be related to structural articular cartilage damage. Femoral torsional deformities have previously been correlated with hip pain and labral damage, and they may contribute to the onset of hip osteoarthritis by exacerbating the effects of existing pathoanatomies, such as cam and pincer morphologies. A comprehensive understanding of the influence of femoral morphotypes on hip joint loading requires subject-specific morphometric and biomechanical data on the movement characteristics of individuals exhibiting varying degrees of femoral torsion. The aim of this study was to evaluate hip kinematics and kinetics as well as muscle and joint loads during gait in a group of adult subjects presenting a heterogeneous range of femoral torsion by means of personalized musculoskeletal models. Thirty-seven healthy volunteers underwent a 3D gait analysis at a self-selected walking speed. Femoral torsion was evaluated with low-dosage biplanar radiography. The collected motion capture data were used as input for an inverse dynamics analysis. Personalized musculoskeletal models were created by including femoral geometries that matched each subject's radiographically measured femoral torsion. Correlations between femoral torsion and hip kinematics and kinetics, hip contact forces (HCFs), and muscle forces were analyzed. Within the investigated cohort, higher femoral antetorsion led to significantly higher anteromedial HCFs during gait (medial during loaded stance phase and anterior during swing phase). Most of the loads during gait are transmitted through the anterior/superolateral quadrant of the acetabulum. Correlations with hip kinematics and muscle forces were also observed. Femoral antetorsion, through altered kinematic strategies and different muscle activations and forces, may therefore lead to altered joint mechanics and pose a risk for articular damage. The method proposed in this study, which accounts for both morphological and kinematic characteristics, might help in identifying in a clinical setting patients who, as a consequence of altered femoral torsional alignment, present more severe functional impairments and altered joint mechanics and are therefore at a higher risk for cartilage damage and early onset of hip osteoarthritis.

Effectiveness of Hip Arthroscopy on Treatment of Femoroacetabular Impingement Syndrome: A Meta-Analysis of Randomized Controlled Trials.

OBJECTIVE: To appraise the highest available evidence provided by randomized controlled trials (RCTs) on the effectiveness of hip arthroscopy versus physical therapy in patients with femoroacetabular impingement syndrome (FAIS). METHODS: Four databases (Medline, Embase, Web of Science, and Scopus) were systematically searched until October 1, 2019. Eligible studies were RCTs in which patients with FAIS underwent hip arthroscopy or physical therapy. The study outcome was the International Hip Outcome Tool, 33 Items (iHOT-33) score, a measure of hip pain, function, and quality of life, assessed at baseline and at the follow-up closer to 12 months after randomization. The pooled mean difference in iHOT-33 scores within and between the treatment arms was computed using a random effects model. The minimum clinically important difference in the iHOT-33 scores was set at 10 points. RESULTS: Three RCTs evaluating iHOT-33 scores between 6 and 8 months after the interventions were included. Significant increases in iHOT-33 scores were observed from baseline to follow-up for both hip arthroscopy (22.3 points [95% confidence interval (95% CI) 17.3-27.4]) and physical therapy (13.0 points [95% CI 9.5-16.4]). Hip arthroscopy demonstrated significantly higher iHOT-33 scores at follow-up compared with physical therapy (10.9 points [95% CI 4.7-17.0]). CONCLUSION: Both hip arthroscopy and physical therapy resulted in statistically and clinically significant short-term improvements in hip pain, function, and quality of life in patients with FAIS. Hip arthroscopy was statistically superior to physical therapy in improving the outcome at follow-up even if improvement may not be detected by patients.

Discriminant validity and reproducibility of spatiotemporal and kinetic parameters during treadmill walking in patients with knee osteoarthritis.

BACKGROUND: Instrumented treadmills are potentially useful tools for the assessment of gait parameters in orthopaedic clinical settings, but their measurement properties remain uncertain. RESEARCH QUESTION: What is the discriminant validity and reproducibility of spatiotemporal and kinetic gait parameters measured by a pressure-instrumented treadmill at different speeds and inclinations in patients with knee osteoarthritis (KOA)? METHODS: A total of 54 patients with unilateral KOA and 23 healthy controls took part in the study. Step length, single-limb support duration and ground reaction force were recorded during level and uphill walking at 3 and 4 km/h using a commercially-available treadmill instrumented with an integrated pressure platform. We examined discriminant validity (difference between involved and uninvolved side as well as against healthy controls) and test-retest reproducibility (reliability and agreement). RESULTS: Significant side differences were observed for single-limb support duration and ground reaction force at touchdown in all conditions (P < 0.05). All the investigated gait parameters showed acceptable reliability and agreement, except step length at 4 km/h uphill. SIGNIFICANCE: We conclude that the pressure-instrumented treadmill used in this study may have good clinical utility for quantitative gait analysis in patients with KOA under different experimental conditions.

Patient-reported outcome measures for hip-related pain: a review of the available evidence and a consensus statement from the International Hip-related Pain Research Network, Zurich 2018.

Hip-related pain is a well-recognised complaint among active young and middle-aged active adults. People experiencing hip-related disorders commonly report pain and reduced functional capacity, including difficulties in executing activities of daily living. Patient-reported outcome measures (PROMs) are essential to accurately examine and compare the effects of different treatments on disability in those with hip pain. In November 2018, 38 researchers and clinicians working in the field of hip-related pain met in Zurich, Switzerland for the first International Hip-related Pain Research Network meeting. Prior to the meeting, evidence summaries were developed relating to four prioritised themes. This paper discusses the available evidence and consensus process from which recommendations were made regarding the appropriate use of PROMs to assess disability in young and middle-aged active adults with hip-related pain. Our process to gain consensus had five steps: (1) systematic review of systematic reviews; (2) preliminary discussion within the working group; (3) update of the more recent high-quality systematic review and examination of the psychometric properties of PROMs according to established guidelines; (4) formulation of the recommendations considering the limitations of the PROMs derived from the examination of their quality; and (5) voting and consensus. Out of 102 articles retrieved, 6 systematic reviews were selected and assessed for quality according to AMSTAR 2 (A MeaSurement Tool to Assess systematic Reviews). Two showed moderate quality. We then updated the most recent review. The updated literature search resulted in 10 additional studies that were included in the qualitative synthesis. The recommendations based on evidence summary and PROMs limitations were presented at the consensus meeting. The group makes the following recommendations: (1) the Hip and Groin Outcome Score (HAGOS) and the International Hip Outcome Tool (iHOT) instruments (long and reduced versions) are the most appropriate PROMs to use in young and middle-aged active adults with hip-related pain; (2) more research is needed into the utility of the HAGOS and the iHOT instruments in a non-surgical treatment context; and (3) generic quality of life measures such as the EuroQoL-5 Dimension Questionnaire and the Short Form Health Survey-36 may add value for researchers and clinicians in this field. We conclude that as none of the instruments shows acceptable quality across various psychometric properties, more methods studies are needed to further evaluate the validity of these PROMS-the HAGOS and iHOT-as well as the other (currently not recommended) PROMS.

Editorial Commentary: Return to Sport: An Ill-Defined Parameter.

Femoroacetabular impingement syndrome (FAIS) is a common cause of hip pain and dysfunction in athletes, which can impair their ability to perform and compete in sports. Hip arthroscopy has become a popular and successful treatment option for the management of FAIS and the return to sport (RTS) of athletes. The concept of RTS has evolved in the last years. Various different factors need to be considered when evaluating RTS after hip arthroscopy for FAIS, such as (1) the definition of RTS (return to participation, RTS, return to performance), (2) the sport type (high-impact vs low-impact) and sport level (professional vs recreational), and (3) the time to follow-up evaluation. In addition, return to high-impact sports, such as soccer, might not be the best recommendation for some patients undergoing hip arthroscopy for FAIS, as it may accelerate the degeneration of the hip joint. Future research should consider all these aspects of the RTS outcome after hip arthroscopy for FAIS. Valid RTS rates are of utmost importance to provide adequate expectations to patients and to guide decision-making of hip surgeons.

Consensus recommendations on the classification, definition and diagnostic criteria of hip-related pain in young and middle-aged active adults from the International Hip-related Pain Research Network, Zurich 2018.

There is no agreement on how to classify, define or diagnose hip-related pain-a common cause of hip and groin pain in young and middle-aged active adults. This complicates the work of clinicians and researchers. The International Hip-related Pain Research Network consensus group met in November 2018 in Zurich aiming to make recommendations on how to classify, define and diagnose hip disease in young and middle-aged active adults with hip-related pain as the main symptom. Prior to the meeting we performed a scoping review of electronic databases in June 2018 to determine the definition, epidemiology and diagnosis of hip conditions in young and middle-aged active adults presenting with hip-related pain. We developed and presented evidence-based statements for these to a panel of 37 experts for discussion and consensus agreement. Both non-musculoskeletal and serious hip pathological conditions (eg, tumours, infections, stress fractures, slipped capital femoral epiphysis), as well as competing musculoskeletal conditions (eg, lumbar spine) should be excluded when diagnosing hip-related pain in young and middle-aged active adults. The most common hip conditions in young and middle-aged active adults presenting with hip-related pain are: (1) femoroacetabular impingement (FAI) syndrome, (2) acetabular dysplasia and/or hip instability and (3) other conditions without a distinct osseous morphology (labral, chondral and/or ligamentum teres conditions), and that these terms are used in research and clinical practice. Clinical examination and diagnostic imaging have limited diagnostic utility; a comprehensive approach is therefore essential. A negative flexion-adduction-internal rotation test helps rule out hip-related pain although its clinical utility is limited. Anteroposterior pelvis and lateral femoral head-neck radiographs are the initial diagnostic imaging of choice-advanced imaging should be performed only when requiring additional detail of bony or soft-tissue morphology (eg, for definitive diagnosis, research setting or when planning surgery). We recommend clear, detailed and consistent methodology of bony morphology outcome measures (definition, measurement and statistical reporting) in research. Future research on conditions with hip-related pain as the main symptom should include high-quality prospective studies on aetiology and prognosis. The most common hip conditions in active adults presenting with hip-related pain are: (1) FAI syndrome, (2) acetabular dysplasia and/or hip instability and (3) other conditions without distinct osseous morphology including labral, chondral and/or ligamentum teres conditions. The last category should not be confused with the incidental imaging findings of labral, chondral and/or ligamentum teres pathology in asymptomatic people. Future research should refine our current recommendations by determining the clinical utility of clinical examination and diagnostic imaging in prospective studies.

Hip muscle strength asymmetries and their associations with hip morphology and symptoms are sex-specific in patients with femoroacetabular impingement syndrome.

OBJECTIVES: To investigate sex-specific differences in hip muscle strength asymmetries, and associations between hip abductor and flexor strength asymmetries, hip morphology and symptoms in patients with femoroacetabular impingement syndrome (FAIS). DESIGN: Cross-sectional study. SETTING: Clinical setting. PARTICIPANTS: Thirty-four patients with FAIS (21 women, 13 men). MAIN OUTCOME MEASURES: Side-to-side strength asymmetries of hip adductor, abductor, internal and external rotator, flexor and extensor muscles were assessed using dynamometry, while hip pain during contractions was evaluated with a visual analogue scale. Hip morphology was assessed on anteroposterior pelvic radiographs and magnetic resonance arthrography images. Hip symptoms were evaluated using the Oxford Hip Score (OHS). RESULTS: Women presented larger hip flexor strength asymmetries than men. In women, hip abductor asymmetries correlated with the OHS and with hip pain during muscle contraction. Hip flexor asymmetries correlated with the alpha angle in men. CONCLUSION: Patients with FAIS demonstrated sex-specific hip muscle strength asymmetries and associations with the underlying hip symptoms and morphology. Women showed larger hip flexor strength asymmetries than men, and their hip abductor strength asymmetries were associated with hip symptoms. In contrast, hip flexor strength asymmetries in men were associated with the severity of the underlying cam morphology.

Evaluation of an examination chair to quantify the hip internal rotation angle.

BACKGROUND: Deformities of the femoral head-neck junction are associated with limited hip internal rotation, which may lead to femoroacetabular impingement and consequently to hip osteoarthritis. This study compared inter- and intra-observer reproducibility of 3 different methods to quantify hip internal rotation. METHODS: 2 investigators assessed hip internal rotation of 30 asymptomatic participants during 2 separate testing sessions. Internal rotation was assessed by rotating the 90°-flexed hip manually while in a supine position (manual), in an examination chair capable of applying a single load (EC1) and in a newly developed examination chair with 5 load levels (EC2). Inter- and intra-observer reproducibility was compared among methods using reliability (intra-class correlation coefficient, ICC) and measurement error (smallest detectable chance). RESULTS: Inter-observer reliability was good for the manual assessment (ICC = 0.83) and excellent for the EC1 and EC2 methods (ICC ⩾ 0.95) with expected measurement errors of 15.9°, 7.1° and 6.8°-14.3°, respectively. Intra-observer reliability was excellent for each method (ICC ⩾ 0.96), although measurement error ranged from 7.6°-11.8° for EC2 and was slightly higher compared to the manual (7.8°) and EC1 (5.9°) methods. CONCLUSIONS: Reproducibility of EC2 hip internal rotation angle assessment is superior to that of the manual assessment at specific load levels but not to the EC1 method. Future assessment devices need to incorporate a means of precisely producing and quantifying the loads applied to the hip joint in order to improve measurement reproducibility.

Standardised measurement of physical capacity in young and middle-aged active adults with hip-related pain: recommendations from the first International Hip-related Pain Research Network (IHiPRN) meeting, Zurich, 2018.

Hip-related pain can significantly impact quality of life, function, work capacity, physical activity and family life. Standardised measurement methods of physical capacity of relevance to young and middle-aged active adults with hip-related pain are currently not established. The aim of this consensus paper was to provide recommendations for clinical practice and research on standardised measurement methods of physical capacity in young and middle-aged active adults with hip-related pain. Four areas of importance were identified: (1) clinical measures (range of motion, muscle strength, functional impairments), (2) laboratory-based measures (biomechanics and muscle function (muscle activity, size and adiposity)), (3) physical activity, and (4) return to sport/performance. The literature was reviewed, and a summary circulated to the working group to inform discussion at the consensus meeting. The working group developed clinical and research recommendations from the literature review, which were further discussed and modified within the working group at the consensus meeting. These recommendations were then presented to all 38 International Hip-related Pain Research Network (IHiPRN) participants for further discussion, refinement and consensus voting. Therefore, the recommendations voted on were based on a combination of current evidence and expert opinion. The consensus meeting voted on 13 recommendations, six of which were clinically orientated, and seven more research specific. We recommended that clinicians working with young and middle-aged active adults with hip-related pain assess strength using objective methods of measurement, and clinically assess performance of functional tasks, including walking and running. Physical activity should be quantified using both self-reported and objective measures, and patient expectations of recovery should be quantified prior to treatment. It was recommended that return to physical activity (including sport and occupation) be quantified, and sport-specific activities should be assessed prior to return to sport. The IHiPRN participants were uncertain regarding recommendations for range of motion assessment. Research recommendations were that the measurement properties of range of motion, strength and functional performance tests be investigated, reported and improved in both clinical and research settings. Reporting of movement-related parameters (biomechanics and muscle function) should be standardised and the relationship among movement-related parameters, symptoms, function, quality of life, and intra-articular and imaging findings should be investigated. Quantification of return to physical activity (including sport and occupational demands) is required in future research, and the return to sport continuum should be used. Future research is required to determine the best criteria for rehabilitation progression and return to physical activity following hip-related pain management.

Physiotherapist-led treatment for young to middle-aged active adults with hip-related pain: consensus recommendations from the International Hip-related Pain Research Network, Zurich 2018.

The 1st International Hip-related Pain Research Network meeting discussed four prioritised themes concerning hip-related pain in young to middle-aged adults: (1) diagnosis and classification of hip-related pain; (2) patient-reported outcome measures for hip-related pain; (3) measurement of physical capacity for hip-related pain; (4) physiotherapist-led treatment for hip-related pain. Thirty-eight expert researchers and clinicians working in the field of hip-related pain attended the meeting. This manuscript relates to the theme of physiotherapist-led treatments for hip-related pain. A systematic review on the efficacy of physiotherapist-led interventions for hip-related pain (published separately) was conducted and found that strong evidence for physiotherapist-led treatments was lacking. Prior to the meeting, draft consensus recommendations for consideration in the meeting were also developed based on the systematic review. The draft consensus recommendations were presented to all of the meeting participants via email, at least 1 week prior to the meeting. At the meeting, these recommendations were discussed, revised and voted on. Six recommendations for clinical practice and five recommendations for research were included and all gained consensus. Recommendations for clinical practice were that (i) Exercise-based treatments are recommended for people with hip-related pain. (ii) Exercise-based treatment should be at least 3 months duration. (iii) Physiotherapist-led rehabilitation after hip surgery should be undertaken. (iv) Patient-reported outcome measures, measures of physical impairment and measures of psychosocial factors should be used to monitor response to treatment. (v) Physical activity (that may include sport) is recommended for people with hip-related pain. (vi) Clinicians should discuss patient expectations, use shared-decision making and provide education. Recommendations for research were (i) Reporting of exercise programmes: Exercise descriptors such as load magnitude, number of repetitions and sets, duration of whole programme, duration of contractile element of exercise, duration of one repetition, time under tension, rest between repetitions, range of motion through which the exercise is performed, and rest between exercise sessions should be reported. (ii) Research should investigate the optimal frequency, intensity, time, type, volume and progression of exercise therapy. (iii) Research should examine the effect of patient education in people with hip-related pain. (iv) Research should investigate the effect of other treatments used in people with hip-related pain (for example: manual therapy, medications, injections). (v) Research should examine the impact of comorbidities and social determinants on treatment effectiveness in people with hip-related pain. Clinicians and researchers working with young to middle-aged active adults with hip-related pain may use these consensus recommendations to guide, develop, test and implement individualised, evidence-based physiotherapist-led rehabilitation programmes.

Quadriceps Neuromuscular Impairments after Arthroscopic Knee Surgery: Comparison between Procedures.

Quadriceps neuromuscular function remains impaired in the short- and long-term following knee arthroscopy for meniscal surgery and/or anterior cruciate ligament (ACL) reconstruction. The aim of this study was to compare quadriceps neuromuscular impairments in patients following meniscal surgery with and without ACL reconstruction. Thirty patients were tested six months after meniscal surgery with (n = 15) and without (n = 15) ACL reconstruction. We bilaterally assessed knee extension maximal voluntary contraction (MVC) torque using dynamometry, vastus lateralis thickness using ultrasound, quadriceps voluntary activation and evoked knee extension torque with transcutaneous electrical stimulation. Patient-reported outcomes were evaluated with the Knee Injury and Osteoarthritis Outcome Score (KOOS). Compared with meniscus patients, ACL patients demonstrated larger asymmetries in MVC torque (15% vs. 5%, p = 0.049) and vastus lateralis thickness (6% vs. 0%, p = 0.021). In ACL patients, asymmetries in MVC torque correlated with asymmetries in evoked torque (r = 0.622, p = 0.013). In meniscus patients, asymmetries in muscle activation correlated with KOOS quality of life (r = 0.619, p = 0.018). Patients demonstrated persistent quadriceps muscle weakness six months after ACL reconstruction, but not after isolated meniscal surgery. Quantitative and/or qualitative muscular changes likely underlie quadriceps muscle weakness in ACL patients, whereas activation failure is associated with poor quality of life in some meniscus patients.

Editorial Commentary: Do Patients With Femoroacetabular Impingement Syndrome Already Show Hip Muscle Atrophy?

Muscle atrophy, fatty degeneration, and strength deficits of the hip abductors, flexors, and even external rotators are well-known clinical and radiologic findings in patients with advanced hip osteoarthritis. More recently, in the context of prearthritic hip diseases, the role of hip muscle function in femoroacetabular impingement syndrome (FAIS) has gained greater focus for hip surgeons. Several studies have shown that patients with FAIS present with activation deficits of the hip muscles, which may result in hip muscle weakness. Nevertheless, previous studies have yet to determine whether young and mainly active patients with FAIS already show hip muscle atrophy. Future research is required to further characterize hip muscle function in patients with FAIS. Of particular interest is the investigation of whether both qualitative (muscle fatty degeneration) and quantitative (muscle atrophy) morphologic alterations of the hip muscles are present in patients with FAIS, as well as whether these alterations are sex specific and/or related to the underlying hip morphology.

Effectiveness of multicomponent lower extremity injury prevention programmes in team-sport athletes: an umbrella review.

OBJECTIVE: To identify which exercise combinations are most effective as part of a lower extremity injury prevention programme for team-sport athletes. DESIGN: Umbrella review. DATA SOURCES: A comprehensive literature search was performed in PubMed, Scopus, Cochrane Library and PEDro databases. Studies published between January 2000 and March 2017 were included in this umbrella review. STUDY ELIGIBILITY CRITERIA: Moderate to high-quality systematic reviews that investigated the effectiveness of a combination of two or more exercise components, that is, strength, agility, plyometrics, balance, stretching, technique, warm-up and functional activity, regarding injury incidence/rate of lower extremity injuries in team-sport athletes. The methodological quality of the included systematic reviews was independently assessed by two reviewers using the Assessing the Methodological Quality of Systematic Reviews measurement tool and the Grading of Recommendations Assessment, Development and Evaluation guidelines were used to assess the overall quality of evidence for particular outcomes. RESULTS: Twenty-four systematic reviews met the inclusion criteria. Multicomponent exercise interventions were effective in reducing the injury incidence/rate of lower extremity, knee, ACL and ankle injuries, but not groin injuries. Strength and balance exercise components were included in 10 of 11 effective injury prevention programmes for the lower extremity, knee, ACL and ankle injuries. SUMMARY/CONCLUSION: Lower extremity injury prevention programmes in team sports are effective in preventing lower extremity, knee, ACL and ankle injuries. Lower extremity muscle strength and balance exercises should be prioritised in lower extremity injury prevention programmes for team-sport athletes.