title: Single-Leg Squat Performance is Impaired 1 to 2 Years After Hip Arthroscopy.
abstract: OBJECTIVE
  To evaluate single-leg squat performance 1-2 years after arthroscopy for intra-articular hip pathology compared with control subjects and the nonsurgical limb, and to investigate whether single-leg squat performance on the operated limb was associated with hip muscle strength.
  
  
  METHODS
  Cross-sectional study.
  
  
  METHODS
  Private physiotherapy clinic and university laboratory.
  
  
  METHODS
  Thirty-four participants (17 women, 36.7 ± 12.6 years) 1-2 years after hip arthroscopy and 34 gender-matched control subjects (17 women, 33.1 ± 11.9 years).
  
  
  METHODS
  Participants performed single-leg squats using a standardized testing procedure. Squat performance was captured using video. Video footage was uploaded and reformatted for analyses. Hip muscle strength was measured with handheld dynamometry using reliable methods.
  
  
  METHODS
  Frontal plane pelvic obliquity, hip adduction, and knee valgus were measured. Repeated measures analysis of variance evaluated between-group differences, with limb as a within-subjects factor (surgical versus nonsurgical) and gender as a between-subjects factor (P < .05).
  
  
  RESULTS
  The hip arthroscopy group demonstrated significantly greater apparent hip adduction (mean difference 2.7°, 95% confidence interval [CI] 0.7°-4.8°) and apparent knee valgus (4.0°, 95% CI 1.0°-7.1°) at peak squat depth compared with control subjects. The operated limb also demonstrated significantly greater pelvic obliquity during single-leg stance compared with the nonsurgical limb (1.2°, 95% CI 0.1°-2.3°). Women had significantly greater apparent hip adduction (standing 1.6°, 95% CI 0.5°-2.6°; peak squat depth 2.4°, 95% CI 0.3°-4.4°) and apparent knee valgus (standing 3.3°, 95% CI 1.8°-4.7°; peak squat depth 3.1°, 95% CI 0°-6.1°). Significant positive correlations were found between frontal plane angles and hip flexor and extensor peak torque (P > .05).
  
  
  CONCLUSIONS
  One to 2 years after hip arthroscopy, deficits in single-leg squat performance exist that have the potential to increase hip joint impingement and perpetuate postoperative symptoms. Rehabilitation after hip arthroscopy should target retraining in functional single-leg positions.
authors.affiliation: Department of Physiotherapy, Melbourne School of Health Sciences, The University of Melbourne, Parkville, Australia; School of Exercise Science, Australian Catholic University, Melbourne, Australia(∗).
authors.forename: Paula C
authors.initials: PC
authors.lastname: Charlton
authors.affiliation: Department of Physiotherapy, Melbourne School of Health Sciences, The University of Melbourne, Parkville, Australia(†).
authors.forename: Adam L
authors.initials: AL
authors.lastname: Bryant
authors.affiliation: Australian Centre for Research into Injury in Sport and its Prevention (ACRISP), Federation University Australia, Ballarat, Australia; School of Health and Rehabilitation Sciences, The University of Queensland, Brisbane, Australia(‡).
authors.forename: Joanne L
authors.initials: JL
authors.lastname: Kemp
authors.affiliation: School of Exercise Science, Australian Catholic University, Melbourne, Australia(¶).
authors.forename: Ross A
authors.initials: RA
authors.lastname: Clark
authors.affiliation: School of Health and Rehabilitation Sciences, The University of Queensland, Brisbane, Australia(§).
authors.forename: Kay M
authors.initials: KM
authors.lastname: Crossley
authors.affiliation: Department of Mechanical Engineering, Melbourne School of Engineering, The University of Melbourne, VIC 3010, Australia(∗∗). Electronic address: n.collins@unimelb.edu.au.
authors.forename: Natalie J
authors.initials: NJ
authors.lastname: Collins
mesh_terms: D000328:Adult; D001182:Arthroscopy / Q000379:methods*; D001696:Biomechanical Phenomena; D003430:Cross-Sectional Studies; D004576:Electromyography; D005260:Female; D006621:Hip Joint / Q000000981:diagnostic imaging / Q000503:physiopathology*; D006801:Humans; D007592:Joint Diseases / Q000175:diagnosis* / Q000503:physiopathology; D007866:Leg / Q000503:physiopathology*; D053580:Muscle Strength / Q000502:physiology; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging / Q000503:physiopathology*; D011187:Posture / Q000502:physiology*; D016059:Range of Motion, Articular / Q000502:physiology*