Identifying common trajectories of joint space narrowing over two years in knee osteoarthritis

Abstract

Objective: Little is known about the natural history of knee osteoarthritis (OA). We sought to identify common patterns of joint space narrowing (JSN) in well-characterized knee OA patients in the placebo arm of a 2-year international study.

Methods: We performed secondary data analyses of 622 adults ages 39-80 years in North America (n = 310) and Europe (n = 312) with symptomatic knee OA. Fluoroscopically positioned semiflexed anteroposterior radiographs were obtained at 0, 12, and 24 months. Group-based trajectory modeling was used to identify distinctive groups of individuals with similar trajectories of JSN, taking into account sex, age, and body mass index.

Results: Seven groups were identified. Four exhibited joint space width (JSW) stability over 2 years representing the most common trajectory (71%), which was unrelated to initial JSW. Atypical courses included slow, rapid, and moderate progressors; most had significant JSN at study entry. Slow progressors (20%) had a mean JSN of 0.2 mm over 2 years. Only 2% of the sample demonstrated rapid JSN (2.1 mm), while 7% had JSN of 0.7 mm. Rapid progressors tended to be men, while slow and moderate progressors were older and heavier.

Conclusion: Most (70%) people with OA demonstrated no significant JSN over 2 years; 20% showed slow progression, 7% had moderate, and 2% had rapid JSN. Progressors tended to have less JSW at study entry and were older and heavier; rapid progressors were more likely to be men. Understanding common patterns of the course of knee OA may offer new opportunities to target those at greatest risk of disability.