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Varus–valgus motion and functional ability in patients with knee osteoarthritis

¹ Jan van Breemen Institute, Center for Rheumatology and Rehabilitation, Amsterdam, The Netherlands
² VU University Medical Center, Department of Rehabilitation Medicine, EMGO Institute, Amsterdam, The Netherlands
³ MOVE Research Institute for Clinical Movement Studies, Amsterdam, The Netherlands
⁴ Amsterdam School of Allied Health Education, Amsterdam

Correspondence to:
M van der Esch, Jan van Breemen Institute, Center for Rheumatology and Rehabilitation. Jan van Breemenstraat 2, 1056 AB Amsterdam, The Netherlands; M.vd.Esch{at}janvanbreemen.nl

Objective: To assess the relationship between knee varus–valgus motion and functional ability, and the impact of knee varus–valgus motion on the relationship between muscle strength and functional ability in patients with osteoarthritis (OA) of the knee.

Methods: Sixty-three patients with knee OA were tested. Varus–valgus motion was assessed by optoelectronic recording and three-dimensional motion analysis. Functional ability was assessed by observation, using a 100 m walking test, a Get Up and Go test, and WOMAC questionnaire. Muscle strength was measured by a computer-driven isokinetic dynamometer. Regression analyses were performed to assess the relationships between varus–valgus motion and functional ability, and to assess the impact of varus–valgus motion on the relationship between muscle strength and functional ability.

Results: In patients with high varus–valgus range of motion, muscle weakness was associated with a stronger reduction in functional ability (ie, longer walking time and Get Up and Go time) than in patients with low varus–valgus range of motion. A pronounced varus position and a difference between the left and right knees in varus–valgus position were related with reduced functional ability.

Conclusions: In patients with knee OA with high varus–valgus range of motion, muscle weakness has a stronger impact on functional ability than in patients with low varus–valgus range of motion. Patients with knee OA with more pronounced varus knees during walking show a stronger reduction in functional ability than patients with less pronounced varus knees or with valgus knees.