Analysis of the factors that correlate with increased knee adduction moment during gait in the early postoperative period following total knee arthroplasty

Background Analysis of dynamic knee loading during gait is essential to prevent mechanical failures following total knee arthroplasty. External knee adduction moment during gait is the primary factor producing medial joint reaction force, and an increase in the moment is directly related to an increase in the medial compartment load on the knee. Methods Knee adduction moment during gait in 39 knees of 32 female patients following a posterior stabilized knee replacement with a single surgeon was evaluated at 1.3 months following surgery. A cut-off moment was determined as mean + 1 standard deviation (SD) of the moment from 10 healthy subjects, and patients’ knees were divided into high- and normal-moment groups. Significant differences in clinical assessments and gait parameters between the two groups were assessed. Results Based on the cut-off moment, 23 knees were grouped into normal knees and 16 knees were grouped into high-moment knees. High-moment knees showed identical femorotibial angles and knee society scores but had greater toe-out angles and medially directed ground reaction forces compared to normal-moment knees. High-moment knees showed strong correlations between peak moment and knee adduction angle, and frontal plain moment arm. Conclusions The clinical significance of a high knee adduction moment following total knee arthroplasty remains unclear, but dynamic frontal alignment during gait is one of the key factors for residual high-moment knees following surgery.