Severity-Dependent Contributions of Knee Adduction Moment Lever Arm Components and Associated Gait Variables in Medial Knee Osteoarthritis.

PURPOSE: To investigate the contribution of knee adduction moment (KAM) lever arm components and examine their relationships with gait variables in Early-mild and Severe osteoarthritis (OA) groups.

METHODS

Female patients with medial knee OA were classified into two groups: Early-mild (Kellgren-Lawrence (KL) grade 1-2, n = 46) and Severe (KL 3-4, n = 40). At the first peak of KAM, we measured the lever arm; the lateral positions of the body center of mass, knee joint center, and foot center of pressure (foot COP); and the frontal plane angles of the trunk, pelvis, hip, and knee. Additionally, foot progression angle and step width were measured. Hierarchical multiple regression determined the contribution of lever arm components, and partial correlation assessed their relationships with gait variables.

RESULTS

In both groups, smaller knee varus angle (Early-mild: β = 0.563; Severe: β = 0.346) and more lateral foot COP position (Early-mild: β = - 0.316; Severe: β = - 0.686) were associated with a shorter lever arm. Knee varus angle and foot COP explained 46.4% and 4.8% of lever arm variance in Early-mild group, and 11.3% and 35.6% in Severe group. Smaller contralateral pelvic drop and greater hip adduction related to smaller knee varus angle. Especially in Early-mild OA, greater toe-in was associated with smaller knee varus. Additionally, greater toe-in and wider step width were related to foot COP closer to the knee.

CONCLUSIONS

The characteristics of the contributions of the lever arm components and related gait variables were revealed in Early-mild and Severe OA. These findings may inform gait strategies to reduce KAM.