The C-reactive Protein but Not Erythrocyte Sedimentation Rate is Associated with Clinical Severity in Patients with Osteoarthritis of the Knee or Hip

Objective: To investigate the association of C-reactive protein (CRP) with symptoms of clinical disease and demographic factors in osteoarthritis (OA). In addition, to compare CRP with erythrocyte sedimentation rate (ESR) in their ability to associate with osteoarthritic symptoms and features.

Methods: A total of 655 consecutive clinic patients with OA of the knee or hip underwent a rheumatic disease examination, completed a clinical health assessment questionnaire (CLINHAQ), and had laboratory tests performed, including hemoglobin, CRP, and ESR.

Results: The median value of CRP was 5.9 micrograms/ml. CRP was significantly associated with functional disability, joint tenderness, pain, fatigue, global severity, and depression. In addition, correlations were noted for body mass index (BMI) and sex. ESR, by contrast, was unassociated with clinical signs or symptoms except for a weak association with functional disability. The best explanatory multiple regression model for CRP in OA includes BMI, functional disability, and joint tenderness count (R-squared 0.159).

Conclusion: CRP is elevated in OA compared to healthy individuals, and is correlated with rheumatic disease signs and symptoms, including HAQ disability, joint count, and pain. The associations, not seen with ESR, appear to be real, but are not strong. An inflammatory component associated with OA can be detected in the serum.