Structure and function of the abductors in patients with hip osteoarthritis: Systematic review and meta-analysis

BACKGROUND: Hip osteoarthritis (OA) is a major cause of morbidity. Rehabilitation for this population focuses on strengthening the hip muscles, particularly the abductors, however the deficit in function of these muscles is unclear. OBJECTIVES: To review the evidence for the differences in structure and function of hip abductors (gluteus medius and minimus and tensor fascia lata) in hip OA. METHODS: A systematic review was conducted using MEDLINE, AMED, CINAHL and SportDISCUS, from the earliest date to September 2013. Studies that compared hip OA patients with controls, or the unaffected contralateral hip were included. Studies needed to report data on an outcome related to gross gluteal muscle function. RESULTS: An initial yield of 141 studies was reduced to 22 after application of inclusion/exclusion criteria. Meta-analysis confirmed greater hip abductor strength in the control group (standardized mean difference - SMD -0.93, 95% CI -1.70 to -0.16) and the unaffected limb (SMD -0.26, 95% CI -0.48 to -0.04). Meta-analyses showed no differences in muscle size either between groups or limbs. Few electromyography studies have been reported and meta-analysis was not possible. CONCLUSION: Hip abductor strength is reduced in OA patients when compared to healthy controls and to the unaffected limb. Data on muscle size and activity is limited.