Static and dynamic loading patterns in knee joints with deformities.

Abstract

Joint loading at the knee for subjects with angular deformity of the joint was determined by dynamic (normal-walking) and static (1-legged-stance) analysis. Sixteen subjects who exhibited varus, valgus or flexion deformity of the knee were examined using a force-platform cinephotographic technique. Comparisons were made with 3 normal subjects. Normal individuals showed 3 characteristic load-peaks corresponding to hamstrings, quadriceps and gastrocnemius muscle contraction. Loading profiles for subjects with knee deformity did not show these peaks; in general, the magnitude of joint force was less in subjects with deformity than in normal subjects. The concept that there is a direct relationship between angulation, magnitude of load and the location of load within the knee (center of pressure) is not supported. Although a general tendency for increased magnitude of total load was observed with increased angulation of the joint in all planes, the relationship was not clearly predictable. The center of pressure was found to vary throughout the stance phase of the gait cycle and was not directly related to the magnitude of angulation of the joint. For example, the center of pressure was located in the medial part of the knee for some subjects with valgus angulation. Individuals apparently can modify force transmission by adopting compensatory mechanisms that result in unloading of the knee. Factors such as pain in the joint, walking speed and deformity are believed to contribute to unloading of the joint. It is easier to compensate for a valgus than for a varus deformity, since knees with varus deformity showed a more predictable loading pattern (location of the center of pressure) than did knees with valgus deformity.