Background Osteoarthritis (OA) is considered a major cause of pain and activity limitations. Activity limitations are defined as difficulties in performing daily activities. Previous studies have shown a slow increase in activity limitations over time in patients with OA, while others have found no change or even a decrease in activity limitations in this group of patients. Nevertheless, there is a high between-patients variability in the course of activity limitations in patients with OA which needs to be further explained.
Objectives To examine the longitudinal association between knee muscle strength and activity limitations in patients with established knee osteoarthritis (OA), over two years.
Methods Data from 186 patients with knee OA part of the Amsterdam Osteoarthritis cohort were gathered at baseline and at two-year follow up. Knee extensor and knee flexor muscle strength were assessed using an isokinetic dynamometer. Activity limitations were assessed using Western Ontario and McMaster University Osteoarthritis Index (WOMAC) - Physical Function subscale, Get Up and Go test (GUG) and the stairs test. Uni- and multivariate linear regression analyses were used to assess the association between changes in muscle strength and changes in activity limitations, adjusting for relevant confounders and baseline activity limitations.
Results There was an overall 16% increase in mean knee muscle strength (p<0.001), 19% increase in knee extensor muscle strength (p<0.001) and 17% increase in knee flexor muscle strength (p<0.001), over two years. Increased average knee muscle strength and knee flexor muscle strength were associated with better self-reported physical function (WOMAC) (b=-5.7, p=0.03 and b=-6.2, p=0.05), decreased time performing the GUG (b=-1.2, p=0.003 and b=-1.4, p=0.05) and decreased time performing the stairs test (b=-4.4, p<0.001 and b=-6.6, p<0.001). Increased extensor muscle strength was only associated with decreased time performing the stairs test (b=-2.7, p<0.001).
Conclusions The increase of knee muscle strength is associated with decreased activity limitations in patients with knee OA, over two years. These results suggest that muscle strength partially explains the between-patients variability in activity limitations.
Disclosure of Interest None declared