Manual therapy in osteoarthritis of the hip: outcome in subgroups of patients

Objective. To investigate whether manual therapy has particular benefit in subgroups of patients defined on the basis of hip function, range of joint motion, pain and radiological deterioration. Methods. The study was performed in the out-patient clinic of physical therapy of a large hospital. Data on 109 patients with OA of the hip (clinical ACR criteria) participating in a randomized clinical trial on the effects of manual therapy were used. The outcomes for hip function (Harris hip score), range of joint motion (ROM) and pain (VAS) were compared for specific subgroups. Subgroups were assigned by the median split method. The interaction effect between subgroup and treatment was tested using multiple regression analysis. Results. No differences were observed in the effect of manual therapy in specific subgroups of patients defined on the basis of baseline levels of hip function, pain and ROM. On the basis of radiological grading of osteoarthritis (OA), we found that patients with severe radiological grading of OA had significantly worse outcome on ROM as a result of manual therapy than patients with mild or moderate radiological grading of OA. Conclusion. A significant interaction effect was found for only 1 out of 12 hypotheses investigated. Therefore, we conclude that there is no evidence for the particular benefit of manual therapy in subgroups of patients.