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Patient gait a result of osteoarthritis, not necessarily mechanical alignment
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NEW ORLEANS — Amount of lateral sway in a patient’s gait is not related to mechanical alignment of the knee so much as it is a function of the presence of osteoarthritis, according to a study presented here.
Marc C. Jacofsky, PhD, presented his group's findings at the 56th Annual Meeting of the Orthopaedic Research Society.
“Several studies have quantified the gait of patients with severe knee osteoarthritis, and these studies have generally focused on varus deformity and accompanying medial compartment osteoarthritis,” Jacofsky said. “Few studies have examined the compensatory mechanisms in neutral aligned or valgus aligned knees that suffer from the same degree of osteoarthritis.
“Our goal was to compare these compensations between groups with different alignment in several stages of osteoarthritis,” he added.
Motion analysis
For the study, researchers looked at 56 patients with advanced knee osteoarthritis (OA) and 41 control subjects. Patients with OA were scheduled to receive total knee replacement prior to visiting the laboratory. Recent radiographs were examined and graded using the Kellgren/Lawrence scale, and mechanical alignment was determined using motion analysis software.
The subjects were retrospectively divided into varus, neutral and valgus groups according to their calculated alignment, and motion data were collected using a 10-camera motion analysis system and four force platforms embedded in the floor as patients walked along an 8-meter walkway.
According to Jacofsky, all of the patients except one showed degradation grade 3 or greater on the Kellgren/Lawrence scale in at least one joint compartment – and all showed signs of degeneration in at least two joint compartments. In addition, 27 were found to have varus alignment, 12 neutral and 17 valgus. No correlation was reported between the front plane mechanical alignment of the knee and the amount of lateral motion of the center of mass, and there were no significant differences between the amount of sway measured for the varus and valgus groups.
Sway
Both groups of patients with the valgus- and varus-aligned knees, Jacofsky reported, swayed to a larger degree than those investigated with neutral-aligned knees, with the valgus group showing a significantly greater level of lateral motion.
Jacofsky said the results indicate that those with OA in both varus- and valgus-aligned knees use increased lateral motion of the body in an attempt to reduce the loads on the knee regardless of its alignment.
- Reference:
McCamley JD, Jacofsky MC, Jacofsky DJ. Changes in gait due to the alignment of a severely osteoarthritic knee. Paper 112. Presented at the 56th Annual Meeting of the Orthopaedic Research Society. March 6-9, 2010. New Orleans.
I put to you that rather than varus causing external rotation, external rotation causes varus, and the opposite – internal rotation causes valgus. Additionally, there are many more women with femoral anteversion who walk in-toed than there are men with femoral anteversion who walk in-toed.
-Kenneth A. Krackow, MD
Professor,
State University of New York at Buffalo Department of Orthopaedics