The following is a summary of “Moderators of the effect of therapeutic exercise for knee and hip osteoarthritis: a systematic review and individual participant data meta-analysis,” published in the July 2023 issue of Rheumatology by Holden et al.
Numerous international clinical guidelines recommend physical therapy as the primary treatment for knee and hip osteoarthritis. Researchers sought to identify individual patient-level moderators of the effect of therapeutic exercise on pain reduction and physical function improvement in individuals with knee osteoarthritis, hip osteoarthritis, or both. They conducted a systematic review and meta-analysis of individual participant data (IPD) of randomized controlled trials comparing therapeutic exercise to non-exercise controls in individuals with knee, hip, or osteoarthritis. From March 1, 2012, to February 25, 2019, they searched ten databases for randomized controlled trials comparing the effects of exercise with non-exercise or other exercise controls on pain and physical function outcomes in persons with knee osteoarthritis, hip osteoarthritis, or both. IPDs were requested from all eligible randomized controlled trials’ principal investigators.
About 12 prospective moderators of interest were investigated to determine whether they were associated with the short- (12 weeks), medium- (6 months), and long-term (12 months) effects of exercise on self-reported pain and physical function relative to non-exercise controls. The overall effects of the intervention were also summarized. IPD from 31 randomized controlled trials (n=4,241 participants) were included in the meta-analysis out of 91 eligible randomized controlled trials that compared exercise with non-exercise controls. Randomized controlled trials included participants with knee osteoarthritis (18 [58%] of 31 trials), hip osteoarthritis (6 [19%] of 31 trials), or both (seven [23%]) and compared heterogeneous exercise interventions to heterogeneous non-exercise controls, with varying risk of bias. Compared to non-exercise controls, therapeutic exercise reduced pain on a standardized 0–100 scale (with 100 corresponding to the worst pain) by a mean difference of –6·36 points (95% CI –8·45 to –4·27, borrowing of strength [BoS] 10·3%, between-study variance [τ2] 21·6) in the short term, –3·77 points (–5·97 to –1·57, BoS 30 Therapeutic exercise also improved physical function on a standardized 0–100 scale (with 100 corresponding to worst physical function), with a difference of –4·46 points in the short term (95% CI –5·95 to –2·98, BoS 10·5%, τ2 10·1), –2·71 points in the medium term (–4·63 to –0·78, BoS 33·6%, τ2 11·9), and –3·39 points in the long term (–4·97 to –1·81, BoS 34·1%, τ2 6·4).
The effect of exercise on pain and physical function outcomes was moderated by baseline pain and physical function. Those with higher self-reported pain and physical function scores at baseline (i.e., inferior physical function) benefited more than those with lower self-reported pain and physical function scores at baseline in the short term (12 weeks). Compared to non-exercise controls, there was evidence of a minor, positive effect of therapeutic exercise on pain and physical function. However, the clinical significance of this effect is questionable, particularly over the medium and long term. As individuals with higher pain severity and poorer physical function at baseline benefited more than those with lower pain severity and better physical function at baseline, it may be prudent to target therapeutic exercise individuals with higher levels of osteoarthritis-related pain and disability.