Risk factors for early radiographic changes of tibiofemoral osteoarthritis

Objective: To evaluate the risk factors for early radiographic changes of knee osteoarthritis. Methods: Subjects (n=114) with unilateral or bilateral grade 0-1 knee osteoarthritis underwent x ray examination of the knees (semiflexed anteroposterior view) and assessment with the Western Ontario and McMaster Universities (WOMAC) Osteoarthritis Index at baseline and 30 months later. Severity of joint space narrowing (JSN) and osteophytosis were graded in randomly ordered serial radiographs by two readers, blinded to the sequence of the films, using standard pictorial atlases. Results: The odds of an initial appearance of radiographic features of knee osteoarthritis at month 30 were more than threefold greater in African Americans than in whites (osteophytosis: odds ratio (OR) 3.30, 95% confidence interval (CI) 1.04 to 10.54; JSN: OR 3.49, 95% CI 1.16 to 10.68). In addition, the appearance of osteophytosis was positively related to baseline stiffness (OR 1.91/2.1 points on the 2-10 WOMAC scale, 95% CI 1.29 to 2.82). Conclusions: The distinction between incident and established, but early, radiographic knee osteoarthritis is difficult because of the limits to which all possible evidence of the disease can be ruled out in a conventional baseline knee radiograph. Nonetheless, our finding that African Americans were at greater risk of early osteophytosis and JSN than other subjects differs from the results of our previous analysis of risk factors for progressive knee osteoarthritis in the same subjects. The development of osteophytes also was associated with joint stiffness. Future investigations should focus on the systemic and local influences that these ostensible risk factors represent.