Background Osteoarthritis (OA) of the knee is a leading cause of activity limitations (e.g. stair-climbing, walking) in Western countries (1), and an important physical determinant of activity limitations is muscle strength (2;3). Recent evidence points out that proprioception and varus-valgus laxity moderate (i.e. alter the strength of) the association between muscle strength and activity limitations (2;3). In early OA the moderating roles of proprioception and laxity have not yet been examined.
Objectives To establish whether proprioception and varus-valgus laxity moderate the association between muscle strength and activity limitations in patients with early symptomatic knee OA.
Methods A cross-sectional study was conducted in a sample of 151 participants with early symptomatic knee OA from the Cohort Hip and Cohort Knee (CHECK) study. 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). Varus-valgus laxity did not moderate the association between muscle strength and activity limitations: the interaction between muscle strength and varus-valgus laxity was not significantly associated with activity limitations.
Conclusions The results of the present study support the theory that in the absence of adequate motor control through poor proprioceptive input, lower muscle strength affects a patient’s level of activities to a greater degree than in the presence of adequate motor control.
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van der Esch M, Steultjens M, Harlaar J, Knol D, Lems W, Dekker J. Joint proprioception, muscle strength, and functional ability in patients with osteoarthritis of the knee. Arthritis Rheum 2007; 57(5):787-793.
Disclosure of Interest None Declared