Clinical, radiographic, and scintigraphic abnormalities of the knee joint have been correlated in a cross sectional study of 100 patients with osteoarthritis. The group comprised 73 women and 27 men with a mean age of 65.7 years. One hundred and ninety one of the 200 knees had clinical (175) or radiographic (185) evidence of osteoarthritis, or both (161). Scintigraphic images of the knees were obtained 4-5 minutes (early phase) and 2.5-3.5 hours (late phase) after intravenous injection of 600 mBq of technetium-99m diphosphonate. Abnormal images were recorded in 162 knees (81%), and six different patterns were detected. Generalised isotope retention around the knee (early or late phase) was less common than focal areas of uptake around the joint margin (early or late phase) or in the patella or subchondral bone (late phase). Some knees with abnormal scans were normal on radiography (n = 7), or vice versa (n = 21). Different scan patterns correlated with different clinical and radiographic features: the generalised pattern correlated with pain (odds ratio (OR) = 45.1) and osteophytes (OR = 48.3); joint line retention correlated with subchondral bone sclerosis on radiography (OR = 62.1); and subchondral bone retention correlated with more severe radiographic changes. It is concluded that different patterns of scintigraphic abnormality reflect various aspects of the disease process of osteoarthritis.