Background In patients with knee osteoarthritis (OA) lower muscle strength is associated with disease progression and activity limitations. Lower muscle strength in this group of patients is determined by several factors, including pain, avoidance of activities and aging. More recently evidence from cross-sectional studies has suggested that inflammation is an additional factor influencing muscle strength in patients with knee OA .
Objectives To examine the associations of elevated serum c-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) with change in muscle strength in patients with established knee 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. Strength of quadriceps and hamstrings muscles was assessed using an isokinetic dynamometer. The association of inflammatory markers with change in knee muscle strength was analysed using uni- and multivariate linear regression models.
Results Patients with elevated CRP values at both baseline and two-years follow up exhibited a lower increase in knee muscle strength over two years (β= -0.22; p=0.01) compared with the group with not elevated levels at both times of assessment. The association persisted after adjustment for relevant confounders. Elevated ESR values at both times of assessment were not significantly associated with change in knee muscle strength (β=-0.05; p=0.49).
Conclusions Our results indicate that elevated CRP values are related to a lower gain in muscle strength over time in patients with established knee OA. Although the mechanism to explain this relationship is not fully elucidated, these results suggest inflammation as a relevant factor influencing muscle strength in this group of patients.
Sanchez-Ramirez DC, van der LM, van der EM, Gerritsen M, Roorda LD, Verschueren S, van Dieen J, Deker J, Lems WF: Association of serum C-reactive protein and erythrocyte sedimentation rate with muscle strength in patients with knee osteoarthritis. Rheumatology (Oxford) 2013, 52: 727-732.
Disclosure of Interest : None declared