Effectiveness of an 11-week exercise intervention for patients with hip or knee osteoarthritis: results of a quasi-experimental pragmatic trial

Objective
To assess the effectiveness of exercise and education in addition to standard care (SC) compared to SC alone in patients with hip or knee osteoarthritis (OA) during 24 months follow-up.

Design
We conducted a quasi-experimental pragmatic clinical trial in care centers of a health insurance company. Overall, 1,030 subjects with hip and/or knee OA were included. The intervention group was recruited from clients participating in a hip/knee training (HKT, n = 515) in addition to SC. The control group (CO, n = 515) receiving SC only was recruited from the insurance database. HKT comprised 8 group sessions (1/week) of exercise and education, complemented by a 11-week structured home-exercise program (2/week). Primary endpoints were change of joint-related pain and function (WOMAC Index, score 0–10) after 3 months. Secondary endpoints related to follow-ups at 6, 12 and 24 months. All patient reported outcome measures were analyzed using linear mixed models (LMMs) investigating a time x treatment effect. A multivariable cox proportional hazards regression model was used to identify differences of joint replacement during follow-up between groups.
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Results
LMMs revealed statistically significant differences in favor of HKT for the primary outcomes WOMAC pain = 0.47 (CI 0.27–0.66; Effect Size (ES) = 0.22, p < 0.001) and WOMAC function = 0.27 (CI 0.11–0.44; ES = 0.13, p < 0.001). HKT was superior to CO for 6, 12, and 24 months as well (ES < 0.2, p ≤ 0.006). HKT was inferior regarding the first incidence of hip or knee AJR during follow-up in comparison to CO (adjusted hazard ratio, HR = 1.57; CI 1.08—2.30; p = 0.020).

Conclusions
This trial demonstrated short-, mid- and long-term superiority of exercise versus control. However, differences were smaller than those reported in previous efficacy trials, raising questions regarding clinical importance. Responder analysis will follow to identify possible predictors for patient responsiveness on an individual level. Further studies should investigate the frequency and reasons for joint replacement following exercise therapy.
Trial registration
German Clinical Trial Register (DRKS00009251). Registered 10 September 2015.