Reviewed by John Baur, PT, DPT, OCS, FAAOMPT
Teirlinck et al examined whether supervised exercise therapy improves pain and function for adults with hip osteoarthritis (OA) and whether additional randomized trials are likely to change the evidence base.1 The review addresses a practical clinical and research question: exercise is already recommended for OA, but compared with knee OA, hip OA has fewer trials, requiring assessment of whether the evidence is sufficient or whether placebo/no-treatment trials are justified.
The authors updated evidence from prior Cochrane reviews by searching CENTRAL, MEDLINE, EMBASE, CINAHL, PEDro, and Web of Science through September 2021. They included randomized controlled trials of adults with clinical and/or radiographic hip OA in which the intervention was supervised, active exercise therapy delivered by a therapist and evaluated as a standalone treatment. Control groups received usual care, education, no treatment, or a waiting-list condition. Multimodal programs and non-exercise physical modalities such as ultrasound, hot packs, or transcutaneous electrical nerve stimulation were excluded. The main outcomes were pain and function measured immediately after treatment and again 6 to 9 months later.
Eighteen trials met the inclusion criteria. The flowchart shows a search process: 10,033 initial citations were reduced to 4,548 after removal of duplicates, 297 were screened in full text, and 18 hip OA studies were ultimately included. The trials were heterogeneous in size and intervention design. Table 1 shows that study arms ranged from very small samples to approximately 100 participants, and the exercise programs varied in format, intensity, frequency, and duration. Most interventions were land-based; one used aquatic exercise. Twelve studies used group-based exercise, while six used individual therapy. Sessions ranged from 30 to 120 minutes, were commonly delivered one to three times weekly, and lasted 5 to 16 weeks. Outcome instruments also varied, including WOMAC, HOOS, VAS, NRS, IRGL, Harris Hip Score, HAQ, DRI, and the 6-minute walk test.
Risk of bias was generally acceptable but not perfect. Table 2 reports that 13 studies had overall low risk of bias, two had moderate risk, and three had high risk. An unavoidable limitation was blinding: because exercise interventions are visible and outcomes were often patient reported, most studies could not blind participants, therapists, or outcome assessors. The authors used GRADE to judge certainty, finding high-quality evidence for pain after treatment and for pain and function at 6 to 9 months, and moderate-quality evidence for function immediately after treatment because of inconsistency.
The pooled results favored exercise therapy, but the effects were modest. Immediately after treatment, exercise improved pain with a standardized mean difference (SMD) of -0.38 and function with an SMD of -0.31. At 6 to 9 months, exercise also favored pain (SMD -0.23) and function (SMD -0.29). The authors defined an SMD of -0.37 or lower as clinically worthwhile, meaning that post-treatment pain just met the numerical threshold, while function and longer-term outcomes were beneficial but of unclear clinical importance. The cumulative forest plots on pages 6 and 7 show that evidence for benefit became statistically significant early for some outcomes and then became more precise as later trials were added, rather than changing direction.
A distinctive feature of this review is its use of cumulative meta-analysis and extended funnel plots to ask whether more trials are needed. The funnel plot did not suggest obvious publication bias. The extended funnel plot on page 8 simulated the impact of adding a future study and showed that only a trial with a much larger effect than current evidence, or an extraordinarily large trial, would move the pooled estimate into a clearly clinically worthwhile range. Their simulation estimated that a new trial using the current post-treatment pain effect would need 74,843 participants to make the pooled effect clearly clinically worthwhile. This is a central finding: more conventional trials comparing exercise with minimal or no treatment are unlikely to change the conclusion.
Overall, the article supports supervised exercise therapy as an effective conservative option for hip OA, while cautioning that the average benefit is small and may not be clearly meaningful for every patient. Its strongest contribution is not simply confirming benefit, but arguing that future research should shift away from repeating exercise-versus-no-treatment comparisons. The authors recommend focusing instead on which patients benefit most, which exercise types are most effective, and what dose, intensity, frequency, and delivery format produce the best outcomes. Clinically, the review reinforces exercise as reasonable, low-risk care, but it also highlights the need for individualized programs and better evidence about responders, moderators, and optimal exercise prescriptions.
Reference
- Teirlinck CH, Verhagen AP, van Ravesteyn LM, et al. Effect of exercise therapy in patients with hip osteoarthritis: a systematic review and cumulative meta-analysis. Osteoarthritis Cartilage Open. 2023;5:100338. doi:10.1016/j.ocarto.2023.100338