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.