Although intra-articular therapy is widely used in the treatment of osteoarthritis (OA), those controlled clinical trials which include placebo groups suggest that there is little to be gained over joint aspiration alone, or even over a simple needle prick. Glucocorticoids may however offer a small additional symptom benefit over one or two weeks. Viscosupplementation may offer a slightly longer benefit. Intra-articular radiotherapy probably confers no benefit. Serious adverse effects are rare but local effects may occur in up to 10% of patients treated with viscosupplements. Future research should always include a placebo group in clinical studies, should clarify the possible benefits of viscosupplementation and should include in vitro work to consider the biological basis for possible actions of intra-articular therapy.