Quantitative microfocal radiography detects changes in OA knee joint space width in patients in placebo controlled trial of NSAID therapy.

Objective: To assess the usefulness of, and define the time course of changes in the features of osteoarthritic (OA) knees measurable using microfocal radiography, and to determine whether it differs in patients taking a nonsteroidal antiinflammatory drug (NSAID).

Methods: Forty-five patients with knee OA were randomly allocated to receive either diclofenac sodium or placebo for 18 months; 33 (17 NSAID, 16 placebo) completed the study. Clinical and 5 x high definition macroradiographic assessments of both knees in standing semiflexed views were carried out at 6-monthly intervals. Precise measurements were taken of the tibial and femoral subchondral thickness and osteophyte size, and of joint space width (JSW) across the narrowest part of the medial and lateral tibiofemoral compartments.

Results: In all knees as a group, there was no statistically significant difference in JSW between treatment groups. However, changes in JSW were significantly different (p < 0.04, multivariate analysis of variance) between treatments in 51 knees with early disease, i.e., those with initially > 50% JSW (22 active, 29 placebo), but not in 15 knees with severe disease, i.e., initially < 50% JSW (10 active, 5 placebo). During the study, osteophyte size in all knees and in those with > 50% JSW increased significantly (p < 0.016; p < 0.008) in the placebo group but remained unchanged in the treatment group. No significant changes were detected in subchondral cortical thickness.

Conclusion: Using microfocal radiography the time course of changes in JSW and osteophyte size of knees with early, but not late OA, was found to differ in both pattern and magnitude in patients receiving NSAID: In knees with late stage OA the JSW progressively decreased irrespective of treatment. The observations may prove useful for the design of future therapeutic trials.