Objectives To examine the associations of elevated serum c-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) with radiographic progression in patients with established knee osteoarthritis (OA), over two-years.
Methods Data from 186 patients with knee OA were gathered at baseline and at two-years follow up. CRP (mg/l) and ESR (mm/l) were measured in serum from patients' blood. Inflammatory markers were considered elevated if CRP>3mg/l or ESR≥20mm/h . Radiographs of the knees were used to assess joint space narrowing (JSN), ostephytes, sclera and cysts in the tibiofemoral (medial and lateral) and patellofemoral compartments, Kellgren and Lawrence (KL) score (0-4) was also determined. Progression was defined as an increase in ≥1 in the radiographic features assessed or total KL score in either knee during follow-up. The association of inflammatory markers with radiographic progression was analyzed using uni- and multivariate linear regression models. Full models were adjusted for age, gender, NSAIDs use, BMI change, comorbidities change and higher radiographic feature or KL score at baseline.
Results Patients with elevated CRP and ESR values at both baseline and at two-years follow-up exhibited no progression in KL score compared with the group without elevated values at both times of assessment, before or after adjustment for relevant confounders. When analyzing the various futures a significant association was found between elevated CRP (OR=2.9, p=0.048) and ESR (OR=4.42, p=0.017) values at both times of assessment and JSN progression in the patellofemoral compartment compared with the group without elevated levels. No association was found between elevated values of CRP and ESR at baseline and at follow-up with radiographic progression of the other features analyzed in the three compartments assessed.
Conclusions Overall this study provides no evidence that persistently elevated CRP and ESR values are related to a radiographic progression in patients with established knee OA, over two years. Our results are in line with previous evidence which has suggested no association between elevated inflammatory markers and progression of OA . Future studies should be performed analyzing this association with local markers of inflammation, instead of systemic inflammatory markers. Additionally, considering the slow progression of the disease, a longer follow-up period might be recommended.
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Kerkhof HJ, Bierma-Zeinstra SM, Castano-Betancourt MC, de Maat MP, Hofman A, Pols HA et al. Serum C reactive protein levels and genetic variation in the CRP gene are not associated with the prevalence, incidence or progression of osteoarthritis independent of body mass index. Ann Rheum Dis 2010; 69(11):1976-1982.
Disclosure of Interest : None declared