People with patellofemoral pain have impaired functional performance, that is correlated to hip muscle capacity.

Objective: To (i) compare objective function in a range of tasks between people with and without patellofemoral pain (PFP); and (ii) evaluate the relationship of objective function with hip muscle capacity and self-reported function in people with PFP.
Design: Cross-sectional.
Settings: Laboratory.
Participants: Thirty-two physically active people (16 with PFP and 16 controls).
Main Outcome Measures: Functional assessments included stair climbing (time), single-legged chair stand (repetitions), step down (repetitions), forward hop for distance and side hop (repetitions). Hip abductor and extensor capacity assessments included power, endurance, isometric and dynamic strength. Self-reported function included the Kujala scale and Patellofemoral sub-scale of the Knee injury and Osteoarthritis Outcome Score (KOOS-PF).
Results: The PFP group was 15% slower climbing stairs (effect size [ES] = 0.90), performed 12% fewer chair stands (ES = 0.62) and forward hopped 20% shorter (ES = 0.79) compared to controls. Lower hip muscle strength and power correlated with lower objective function (r = 0.52-0.78). Lower Kujala scores correlated with longer stair climbing time (r = -0.53).
Conclusion: People with PFP have objective functional impairments, that are associated with reduced hip muscle capacity, indicating progressive resistance training may be beneficial. Absence of a strong correlation between self-reported, and objective, function indicates assessment of both when treating people with PFP is warranted.
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