Proprioception, laxity, muscle strength and activity limitations in early symptomatic knee osteoarthritis: results from the CHECK cohort.

OBJECTIVE To establish whether proprioception and varus-valgus laxity moderate the association between muscle strength and activity limitations in patients with early symptomatic knee osteoarthritis. DESIGN A cross-sectional study. SUBJECTS A sample of 151 participants with early symptomatic knee osteoarthritis from the Cohort Hip and Cohort Knee study. METHODS Regression analyses were performed to establish the associations between muscle strength, proprioception (knee joint motion detection threshold in the anterior--posterior direction), varus-valgus laxity and activity limitations (self-reported and performance-based). Interaction terms were used to establish whether proprioception and laxity moderated the association between muscle strength and activity limitations. RESULTS Proprioception moderated the association between muscle strength and activity limitations: the negative association between muscle strength and activity limitations was stronger in participants with poor proprioception than in participants with accurate proprioception (performance-based activity limitations p = 0.02; self-reported activity limitations p = 0.08). The interaction between muscle strength and varus-valgus laxity was not significantly associated with activity limitations. CONCLUSION The results of the present study support the theory that in the absence of adequate proprioceptive input, lower muscle strength affects a patient's level of activities to a greater degree than in the presence of adequate proprioceptive input.