EULAR report on the use of ultrasonography in painful knee osteoarthritis. Part 1: prevalence of inflammation in osteoarthritis

Abstract

Objectives: To assess the prevalence of inflammation in subjects with chronic painful knee osteoarthritis (OA), as determined by the presence of synovitis or joint effusion at ultrasonography (US); and to evaluate the correlation between synovitis, effusion, and clinical parameters.

Methods: A cross sectional, multicentre, European study was conducted under the umbrella of EULAR-ESCISIT.

Subjects: had primary chronic knee OA (ACR criteria) with pain during physical activity >or=30 mm for at least 48 hours. Clinical parameters were collected by a rheumatologist and an US examination of the painful knee was performed by a radiologist or rheumatologist within 72 hours of the clinical examination. Ultrasonographic synovitis was defined as synovial thickness >or=4 mm and diffuse or nodular appearance, and a joint effusion was defined as effusion depth >or=4 mm.

Results: 600 patients with painful knee OA were analysed. At US 16 (2.7%) had synovitis alone, 85 (14.2%) had both synovitis and effusion, 177 (29.5%) had joint effusion alone, and 322 (53.7%) had no inflammation according to the definitions employed. Multivariate analysis showed that inflammation seen by US correlated statistically with advanced radiographic disease (Kellgren-Lawrence grade >or=3; odds ratio (OR)=2.20 and 1.91 for synovitis and joint effusion, respectively), and with clinical signs and symptoms suggestive of an inflammatory "flare", such as joint effusion on clinical examination (OR=1.97 and 2.70 for synovitis and joint effusion, respectively) or sudden aggravation of knee pain (OR=1.77 for joint effusion).

Conclusion: US can detect synovial inflammation and effusion in painful knee OA, which correlate significantly with knee synovitis, effusion, and clinical parameters suggestive of an inflammatory "flare".

Figures

Figure 1

Synovitis at ultrasonography in subjects with painful knee OA: distribution of synovial thickness.

Figure 2

Effusion depth on ultrasonography in subjects with painful knee OA: distribution of effusion depth.

Figure 3

Relationship between ultrasonography synovial thickness and effusion depth using linear regression.

Figure 4

Synovitis (A) and joint effusion (B) on US in subjects with painful knee OA. (A) Synovitis in a longitudinal scan (suprapatellar recess). (B) Joint effusion in a longitudinal scan (suprapatellar recess): S, synovitis; E, effusion.