Varus-valgus motion and functional ability in patients with knee osteoarthritis.
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.
van der Esch
M
M
Jan van Breemen Institute, Center for Rheumatology and Rehabilitation. Jan van Breemenstraat 2, 1056 AB Amsterdam, The Netherlands. M.vd.Esch@janvanbreemen.nl
Steultjens
M
M
Harlaar
J
J
Wolterbeek
N
N
Knol
D
D
Dekker
J
J
D000368:Aged; D004185:Disability Evaluation; D005260:Female; D005684:Gait; D006801:Humans; D007719:Knee Joint / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D053580:Muscle Strength; D018908:Muscle Weakness / Q000209:etiology / Q000503:physiopathology; D018482:Muscle, Skeletal / Q000503:physiopathology; D020370:Osteoarthritis, Knee / Q000150:complications / Q000503:physiopathology*; D016059:Range of Motion, Articular; D012720:Severity of Illness Index; D016138:Walking; D016474:Weight-Bearing