Objective To study the relationship between serum C reactive protein (CRP) levels, genetic variation in the CRP gene and the prevalence, incidence and progression of radiographic osteoarthritis (ROA) in the Rotterdam Study-I (RS-I). A systematic review of studies assessing the relationship between osteoarthritis (OA) and CRP levels was also performed.

Methods The association between CRP levels and genetic variation in the CRP gene and ROA was examined in 861 patients with hand OA, 718 with knee OA, 349 with hip OA and 2806 controls in the RS-I using one-way analysis of covariance and logistic regression, respectively. PubMed was searched for articles published between January 1992 and August 2009 assessing the relationship between CRP levels and OA.

Results In RS-I the prevalence of knee OA, but not hip OA or hand OA, was associated with 14% higher serum CRP levels compared with controls (p=0.001). This association disappeared after adjustment for age and especially body mass index (BMI) (p=0.33). Genetic variation of the CRP gene was not consistently associated with the prevalence, incidence or progression of OA within RS-I. The systematic review included 18 studies (including RS-I) on serum CRP levels and the prevalence, incidence or progression of OA. Consistently higher crude CRP levels were found in cases of prevalent knee OA compared with controls. No association was observed between serum CRP levels and the prevalence of knee OA following adjustment for BMI (n=3 studies, meta-analysis p value=0.61).

Conclusion There is no evidence of association between serum CRP levels or genetic variation in the CRP gene with the prevalence, incidence or progression of OA independent of BMI.