Efficacy of Exercise-Based Rehabilitation Programs for Improving Muscle Function and Size in People with Hip Osteoarthritis: A Systematic Review with Meta-Analysis

SIMPLE SUMMARY: Hip osteoarthritis (OA) is characterised by increased pain and functional disability. People with hip OA also have reduced muscle size and weakness, especially in the muscles surrounding the hip. Current exercise-based rehabilitation programs aim to reduce clinical symptoms and improve physical function. High-intensity resistance exercises can improve muscles strength in people with knee OA; however, the efficacy of these exercises to improve muscle function and size in people with hip OA has received less attention. Therefore, the aim of this review was to identify whether current rehabilitation programs involving high-intensity exercises could improve muscle size and function in people with hip OA. The findings support increased hip abduction strength, favouring a high-intensity resistance intervention when compared to a control group in people with hip OA. However, no differences were observed in hip or knee muscle function or size when comparing high-intensity resistance to low-intensity resistance interventions. This review also highlighted the dearth of studies that evaluate muscle outcomes following current rehabilitation programs in people with hip OA. Therefore, future studies should include measurements of muscle function and size when evaluating the effects of current rehabilitation programs in people with hip OA. ABSTRACT: Objective: To determine the effect of exercise-based rehabilitation programs on hip and knee muscle function and size in people with hip osteoarthritis. Methods: Seven databases were systematically searched in order to identify studies that assessed muscle function (strength or power) and size in people with hip osteoarthritis after exercise-based rehabilitation programs. Studies were screened for eligibility and assessed for quality of evidence using the GRADE approach. Data were pooled, and meta-analyses was completed on 7 of the 11 included studies. Results: Six studies reported hip and/or knee function outcomes, and two reported muscle volumes that could be included in meta-analyses. Meta-analyses were conducted for four strength measures (hip abduction, hip extension, hip flexion, and knee extension) and muscle size (quadriceps femoris volume). For hip abduction, there was a low certainty of evidence with a small important effect (effect size = 0.28, 95% CI = 0.01, 0.54) favouring high-intensity resistance interventions compared to control. There were no other comparisons or overall meta-analyses that identified benefits for hip or knee muscle function or size. Conclusion: High-intensity resistance programs may increase hip abduction strength slightly when compared with a control group. No differences were identified in muscle function or size when comparing a high versus a low intensity group. It is unclear whether strength improvements identified in this review are associated with hypertrophy or other neuromuscular factors.