The frequency and severity of ultrasound-detected osteoarthritis features in the knees and their associations with pain: Cross-sectional analyses of the Nor-Hand study.

Objective: To investigate the frequency and severity of ultrasound-detected osteophytes and synovitis in people with and without knee osteoarthritis (OA), and to explore the association between these ultrasound features and pain. Design: In the Nor-Hand study, both knees were assessed for osteophytes (0-3 scale, four locations per knee) and grey-scale synovitis (0-3 scale). The frequency and severity of the ultrasound-detected features were compared in individuals with and without knee OA defined by the American College of Rheumatology criteria. Pain was self-reported in each knee (yes/no) and by the Western/Ontario McMaster University index (WOMAC). The associations between ultrasound-detected features and pain were examined by regression analyses adjusted for age, sex, and body mass index. Results: We analyzed 286 participants. Osteophytes of all sizes were more common in participants with knee OA compared to those without (65.9 ​% vs. 40.8 ​%, p ​< ​0.001). No between-group difference was found for the frequency of any grey-scale synovitis (45.5 ​% vs. 44.7 ​%, p ​= ​0.67), while severe synovitis was more common in those with knee OA. Ultrasound-detected osteophyte sum score, but not synovitis, was associated with WOMAC pain (B ​= ​0.18, 95 ​% CI 0.03-0.32). Osteophytes of all sizes were associated with pain in the same knee with odds ratio (OR, 95 ​% CI) ranging from 1.85 (1.20-2.84) to 9.02 (4.04-20.10). Statistically significant association was found for severe synovitis only (OR ​= ​6.63, 95 ​% CI 2.26-19.43). Conclusions: Ultrasound-detected osteophytes were prevalent in people with knee OA and were associated with pain. OA pathology in individuals without fulfilling the knee OA criteria may reflect early or subclinical OA.