Association between clinical and sonographic synovitis in patients with painful knee osteoarthritis

To evaluate the association between ultrasonographic findings of inflammation (effusion, synovitis) and clinical findings in patients with primary painful knee osteoarthritis.

This cross-sectional study was performed on 142 patients with primary painful knee osteoarthritis (American College of Rheumatology criteria) in whom the visual analogue scale of pain was 30 or more. Clinical parameters were evaluated by a rheumatologist using Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score while the ultrasonographic examination was performed by a musculoskeletal radiologist in our center. Knee joint synovitis and effusion were defined as synovial thickness ≥ 4 mm and depth of fluid in the suprapatellar recess ≥ 4 mm, respectively.

Sixty-eight (47.9%) patients demonstrated neither synovitis nor effusion, 37 (26.1%) had only effusion, 11 (7.7%) had only synovitis and 26 (18.3%) had both effusion and synovitis in the ultrasonographic examination. There was significant association between ultrasonographic knee arthritis (defined as presence of synovitis or effusion) and WOMAC pain sub-score, WOMAC physical function sub-score and WOMAC total score. No significant association was noted between sonographic signs of arthritis and WOMAC joint stiffness sub-score. We also found significant correlation between ultrasonographic synovitis and WOMAC pain sub-score (P < 0.001), WOMAC physical function sub-score (P < 0.001) and total WOMAC score (P < 0.001).

This study revealed a positive correlation between ultrasonographic synovitis and total WOMAC score, WOMAC pain and physical function sub-score. There was no association between sonographic signs of arthritis and WOMAC joint stiffness sub-score.