Variable Stiffness Shoe Alters Muscle Activations and Knee Joint Moments

Medial compartment knee osteoarthritis (OA) is nearly 10 times more common than lateral compartment OA [1] and develops in approximately 20-40 % of adults over the age of 60 [2]. A high maximum knee adduction moment in walking has been associated with OA rate of progression, treatment outcome, and disease severity. The use of a shoe intervention with a more rigid lateral compared to medial midsole, referred to as a variable stiffness shoe (VS), can reduce the knee adduction moment magnitude in both healthy persons [3] and osteoarthritis patients[4]. Initial investigations with this VS shoe have also found that only a small portion of the variability in the absolute change in the maximum knee adduction moment is explained by the peak magnitude in a neutral shoe and that secondary changes in the hip and ankle frontal plane moments accompany changes in the knee adduction moment [3; 5]. These results suggest that an important dynamic response by the lower extremity muscles may be involved in the adaptation to this intervention and thus the reduction of the knee adduction moment during walking.