OBJECTIVES: There is considerable evidence that an abnormally high knee adductor moment is a characteristic of the gait patterns in people with knee osteoarthritis (OA). The aim of this study was to examine the relationship between the peak knee adduction moment during the early and late stance phases of gait, and medial and lateral tibial bone size and cartilage volume in healthy women. METHODS: Three-dimensional Vicon gait analyses and magnetic resonance imaging (MRI) were performed on 20 healthy women without knee OA. The external knee adduction moment was correlated with medial and lateral tibial bone size and cartilage volume for the dominant leg. RESULTS: The knee adduction moment significantly correlated with the bone size of the medial tibial plateau (r = 0.63, P < 0.005), but was not related to the bone size of the lateral plateau. No relationship was observed between the knee adduction moment and medial or lateral tibial cartilage volume. CONCLUSIONS: Although the knee adduction moment was positively associated with the bone size of the medial tibial plateau, it appeared to have little effect on cartilage volume in that compartment in healthy women. It may be that the effect of the knee adduction moment differs in healthy subjects compared with those with established knee OA.