Definitions of osteoarthritis in the knee and hand.

Osteoarthritis is the most common joint disorder, with a prevalence that increases with age. In 80 year old women radiologically defined osteoarthritis is found in over 70% in the distal interphalangeal joints (DIP) and in approximately 50% in the knees.' Osteoarthritis is characterised by pain on movement, and the pathophysiological processes can be visualised radiologically. Radiographic findings include degenerative features (marginal osteophytes, subchondral cysts, loose bodies), reparative features (marginal osteophytes, subchondral sclerosis), and inflammatory features (oint effusions, bursar extension). Based on these features several radiological criteria have been developed for both the knees23 and hands.2 5 Recently the American Colleges ofRheumatology also have suggested clinical criteria for osteoarthritis of the knee,6 hip,7 and hand.8 The clinical criteria were chiefly developed to enable correct classification of patients in clinical studies, whereas radiological criteria can be used both for diagnosis and evaluation of disease progress. In most published reports, a rating of grade 2 or more (definite osteophytes and possible joint space narrowing) on the 0-4 graded radiographic scale developed by Kellgren and Lawrence2 has been used as the gold standard for diagnosis. Despite a positive correlation between the Kellgren-Lawrence scale and pain, only 55-85% and 11-28% of those with grade 3-4 changes in the knees and hands, respectively, have symptoms of pain.9 When reviewing and developing criteria for diagnosis and progression in osteoarthritis several characteristics should be considered. The criteria should be associated with symptoms, reflect the disease process, and predict long term outcome. For scientific studies they should also be accurate, reproducible, convenient to use, and relatively inexpensive.