© 2004 Canadian Medical Association or its licensors Research

Osteoarthritis is a degenerative joint disease affectingarticular cartilage and underlying bone, commonlyof the knee.1 Current treatment includes the oral use of NSAIDs, either nonselective or cyclooxygenase-2 (COX-2)-selective. These agents carry a substantial risk of clinically significant adverse effects, particularly on the gas-trointestinal2,3 and renal systems.4 Although the incidence of gastrointestinal complications has been reported to be lower with COX-2-selective NSAIDs than with nonselective NSAIDs,5–7 the former have been linked to adverse renal ef-fects8 and an increased risk of cardiovascular complications.9 The need for safer treatment of osteoarthritis has led to research into the topical use of NSAIDs.10–12 Recent reviews of the few published placebo-controlled studies suggest that topical NSAID therapy can relieve pain13–15 with few gas-trointestinal side effects.16 Current practice guidelines advo-cate the use of topical therapy, including NSAIDs, in the management of osteoarthritis.17–19 A diclofenac solution con-taining the absorption enhancer dimethyl sulfoxide (DMSO) was developed for site-specific topical application. The ob-jective of this study was to demonstrate that applying this so-lution to a painful knee with primary osteoarthritis could provide symptom relief with minimal systemic side effects. Methods Investigators from 7 medical centres in southern Ontario re-cruited patients for this study. The study was approved by the Committee for Research on Human Subjects of the Toronto Hos-pital’s Medical Research Directorate and by similar committees at all other participating sites. After providing written informed con-sent, patients were screened and 248 were selected according to predetermined criteria. Inclusion criteria were as follows: primary osteoarthritis in at least 1 knee, verified radiologically within the previous 6 months and scored (as normal, minimal, moderate or marked) for joint-space narrowing and marginal osteophytes in the medial, lateral and patellofemoral compartments;20,21 at least moder-Effect of a topical diclofenac solution for relieving symptoms of primary osteoarthritis of the knee: a randomized controlled tria