Synovitis linked to constant pain in knee OA

Moderate to severe synovitis is significantly associated with constant pain in patients with knee osteoarthritis (OA), reveals a study.

Notably, inflammation appears to play a “context-specific role across pain experiences, especially in earlier radiographic stages of knee OA,” the authors said.

A total of 248 patients (453 knees) with radiographically early-stage (Kellgren-Lawrence arthritis grading scale [KL] ≤2) and late-stage (KL ≥3) disease and frequent symptoms underwent musculoskeletal ultrasound (US) measures of inflammation using the Outcome Measures in Rheumatology (OMERACT) knee US scoring system. The Measure of Intermittent and Constant Osteoarthritis Pain (ICOAP) tool was used to capture pain experiences.

The authors examined the association between US-synovitis and ICOAP pain experiences using a series of linear, logistic, or multinomial logistic regression models (as appropriate for each variable), adjusted for age, sex, body mass index, and radiographic stage. They also carried out secondary analyses by radiographic stage.

Worse synovitis correlated with higher ICOAP constant pain scores (β, 8.05, 95 percent confidence interval [CI], 0.67‒15.43), but not with intermittent pain scores. Moreover, moderate to severe synovitis correlated with significantly greater constant pain pattern (relative risk, 4.92, 95 percent CI, 1.06‒17.00).

Secondary analyses revealed that moderate to severe synovitis in early radiographic OA correlated with 2.70-higher odds (95 percent CI, 1.04‒7.02) of any constant pain, 3.28-higher odds (95 percent CI, 1.43‒7.52) of any intermittent pain, and higher intermittent (β, 10.47, 95 percent CI, 1.03‒19.91) and constant (β, 12.62, 95 percent CI, 3.02‒22.23) pain scores.

There were no associations for synovitis observed in patients with late radiographic OA.