Severity and extent of osteoarthritis and low grade systemic inflammation as assessed by high sensitivity C reactive protein

Background: Although osteoarthritis (OA) is thought to derive from defective chondrocyte metabolism and thus inherently lack the large scale systemic response of rheumatoid arthritis, there is increasing interest in the acute phase proteins in OA. Objective: To assess the association between high sensitivity C reactive protein (hsCRP) and severity and extent of OA in patients with advanced hip and knee OA. Methods: Preoperative hsCRP was measured in frozen serum samples from 770 consecutive patients with hip or knee joint replacement due to advanced OA recruited between 1995 and 1996. Pain was measured by a visual analogue scale and the Western Ontario and McMaster Universities OA index (WOMAC). The extent of OA in different joints was assessed clinically and radiographically. Results: The (geometric) mean hsCRP was 2.5 mg/l among all patients. Severity of pain was associated with mean hsCRP (adjusted elevation highest v lowest quintile=35%, p=0.01) after controlling for known or suspected predictors of hsCRP, including age, smoking, and body mass index. Neither the bilateral nor the generalised extent of OA, nor any of the dimensions of the WOMAC were associated with mean hsCRP levels. Conclusions: Severity of pain, but not extent of OA, was associated with hsCRP levels in this group of patients with advanced OA. Longitudinal studies with repeated assessments of hsCRP and pain are needed to assess the possible value of hsCRP for monitoring or predicting the clinical course of OA.