The influence of foot progression angle on the knee adduction moment during walking and stair climbing in pain free individuals with knee osteoarthritis

The external knee adduction moment during walking and stair climbing has a characteristic double hump pattern. The magnitude of the adduction moment is associated with the development and progression of medial compartment knee osteoarthritis (OA). There is an inverse relationship between the magnitude of the second peak adduction moment and foot progression angle (FPA). Increasing FPA beyond a self-selected degree of toe-out may further reduce the magnitude of this moment for persons with knee OA. In this study, subjects with medial compartment knee OA walked and climbed stairs using their natural (i.e. self-selected) and an increased FPA (i.e. self-selected + 15° of additional toe-out). Increasing FPA did not change the magnitude of the first peak adduction moment but it did significantly decrease the second peak during walking. The first peak moment during stair ascent was significantly greater for the increased FPA condition, and a significant reduction was noted for the second peak. No significant differences were noted during stair descent. These results suggest that walking with a toe-out strategy may benefit persons with early stages of medial knee OA.