To determine the prevalence of generalized osteoarthritis in patients with knee osteoarthritis.

Patients with knee osteoarthritis were recruited for a therapeutic trial via press announcement and selected based on American College of Rheumatology radioclinical criteria for femorotibial arthritis. Patients were asked to bring all their radiographs to the study visits, which included a physical examination. Each patient had an inclusion visit and a second visit 1 month later. The study physicians used a standardized chart to indicate clinical and radiographic evidence of osteoarthritis in each patient. At the hands and feet, the presence of clinical criteria was sufficient for the diagnosis of osteoarthritis. The shoulders and elbows were not assessed. Three criteria sets for generalized osteoarthritis were evaluated: Kellgren and Moore criteria (Heberden’s nodes or interphalangeal osteoarthritis), ACR criteria (osteoarthritis of the spine and at least two other joints), and Dougados criteria (bilateral finger osteoarthritis or osteoarthritis of the spine and both knees).

We included 302 patients for whom the side affected with knee osteoarthritis was known. Mean symptom duration was 5.9±5.7 years, mean number of painful flares was 10.1±9.4, mean number of joints with osteoarthritis was 2.6±1.8, and mean body mass index was 29.5±5.3kg/m². A family history of osteoarthritis was noted in 154 (51%) patients and spinal osteoarthritis in 148 (49%) patients. Kellgren-Moore criteria for interphalangeal osteoarthritis were met in 42 (13.9%) patients, ACR criteria by 124 (41%) patients, and Dougados criteria by 127 (42%) patients. In all, 156 (52%) patients met at least one of the three definitions of generalized osteoarthritis.

More than half the patients included in a therapeutic trial in knee osteoarthritis had generalized osteoarthritis with maximum symptoms at the knee at baseline. Some patients with osteoarthritis in multiple joints met none of the three criteria sets for generalized osteoarthritis. Further studies are needed to assess the sensitivity and specificity of current criteria sets and, if needed, to identify new criteria.