Abstract
OBJECTIVE: To evaluate risk factors for progressive radiographic changes of knee osteoarthritis using a standardised fluoroscopically assisted protocol for knee radiography. SUBJECTS: (n = 319) with unilateral or bilateral knee osteoarthritis underwent a fluoroscopically standardised x ray examination of the knees (semiflexed AP view) and assessment with the Western Ontario and McMaster Universities (WOMAC) osteoarthritis index at baseline and at 30 months. Tibiofemoral joint space narrowing and osteophytosis were graded in randomly ordered serial radiographs by consensus of two readers using standard pictorial atlases. RESULTS: Progression of joint space narrowing was inversely related to baseline joint space width (odds ratio (OR) = 0.67/1.4 mm (95% confidence interval (CI), 0.49 to 0.91)) and positively associated with patellofemoral osteoarthritis (OR = 3.36 (1.83 to 6.18)). Osteophyte growth was inversely related to overall severity (number and size) of osteophytosis at baseline (OR = 0.47/1.8 points on a 12 point osteophyte severity scale (95% CI, 0.33 to 0.66)), and directly related to baseline stiffness (OR = 1.39/2.1 WOMAC scale points (95% CI, 1.09 to 1.77)) and the presence of patellofemoral osteoarthritis at baseline (OR = 2.31 (1.37 to 3.88)). CONCLUSIONS: Progression of both joint space narrowing and osteophyte growth are predicted by the severity of the respective radiographic features of osteoarthritis at baseline and by the presence of patellofemoral osteoarthritis. In addition, knee stiffness is a risk factor for progressive osteophyte growth.