Single leg squat performance is impaired one to two years after hip arthroscopy

1 2 Objective: 1. Evaluate single leg squat performance 1-2 years after arthroscopy for intra3 articular hip pathology, compared to controls and the non-operative limb. 2. Investigate 4 whether single leg squat performance on the operated limb was associated with hip muscle 5 strength. 6 Design: Cross-sectional study 7 Setting: Private physiotherapy clinic and university laboratory. 8 Participants: Thirty-four participants (17 females, 36.7±12.6 years) 1-2 years following hip 9 arthroscopy, and 34 sex-matched controls (17 females, 33.1±11.9 years) 10 Methods: Participants performed single leg squats using a standardized testing procedure. 11 Squat performance was captured using video. Video footage was uploaded and reformatted 12 for analyses. Hip muscle strength was measured with hand-held dynamometry using reliable 13 methods. 14 Outcome measures: Frontal plane pelvic obliquity, hip adduction and knee valgus were 15 measured. Repeated measures analysis of variance evaluated between-group differences, with 16 limb as a within-subjects factor (operated versus non-operated) and sex as a between-subjects 17 factor (p<.05). 18 Results: The hip arthroscopy group demonstrated significantly greater apparent hip 19 adduction (mean difference 2.7°, 95% CI 0.7° to 4.8°) and apparent knee valgus (4.0°, 95% 20 CI 1.0° to 7.1°) at peak squat depth, compared to controls. The operated limb also 21 demonstrated significantly greater pelvic obliquity during single leg stance compared to the 22 M AN US CR IP T AC CE PT ED ACCEPTED MANUSCRIPT 2 non-operated limb (1.2°, 95% CI 0.1° to 2.3°). Females had significantly greater apparent hip 23 adduction (standing 1.6°, 95% CI 0.5° to 2.6°; peak squat depth 95% CI 2.4°, 0.3° to 4.4°) 24 and apparent knee valgus (standing 3.3°, 95% CI 1.8° to 4.7°; peak squat depth 3.1°, 95% CI 25 0° to 6.1°). Significant positive correlations were found between frontal plane angles and hip 26 flexor and extensor peak torque (p>.05). 27 Conclusion: 1-2 years after hip arthroscopy, deficits in single leg squat performance exist 28 that have the potential to increase hip joint impingement and perpetuate post-operative 29 symptoms. Rehabilitation post-hip arthroscopy should target retraining in functional single 30 leg positions. 31 32 Key terms: hip arthroscopy, chondrolabral pathology, single leg squat, functional 33 impairment 34