To clarify the evidence on the magnitude and duration of treatment effect of intra-articular corticosteroid (IAC) injections for knee osteoarthritis (OA) compared to placebo, to evaluate a treatment effect by steroid type, and to describe the reported adverse effects.
Cochrane Controlled Trials Register, Medline, Embase, CINAHL, Scopus, and Web of Science databases were searched. The risk of systematic bias was assessed according to the Cochrane Collaboration’s domain-based evaluation framework.
The final sample included eight RCTs with follow-ups from 1 to 26 weeks. The risk of systematic bias was considered low in five and high in three studies. The pooled SMD was -0.58 (95% CI -0.88 to -0.27) and NNT 5.1 (95% CI 10.0 to 3.7). The heterogeneity was considerable. The pooled effect size approached the level of statistical insignificance at four months. The pooled risk ratio of adverse effects was insignificant 0.95 (95% CI 0.34 to 2.55).
The IAC had a mild to moderate effect on pain severity up to three months after the injection – much longer than it had previously been reported. The effect may vary substantially in different patient groups and appropriate patient selection is important. The risk of adverse effects was low.