Impact of ankle osteoarthritis on the energetics and mechanics of gait: the case of hemophilic arthropathy.

BACKGROUND: Osteoarthritis may affect joints in any part of the body, including the ankle. The purpose of this study was to assess the impact of ankle osteoarthritis on the energetics and mechanics of gait, while taking into account the effect of slower speed generally adopted by patients with osteoarthritis. METHODS: Using a motion analysis system, synchronous kinematic, kinetics, spatiotemporal, mechanics and metabolic gait parameters were measured in 10 patients diagnosed with ankle osteoarthritis consecutive to hemophilia. The subjects walked at a self-selected speed and their performance was compared to speed-matched normal values obtained in healthy control subjects. FINDINGS: Speed-normalization using a Z-score transformation showed a significant increase in metabolic cost (Z=1.78; P=0.006) and decrease in mechanical work (Z=-0.97; P=0.009). As a consequence, muscular efficiency also decreased (Z=-0.97; P=0.001). These changes were associated with a surprising efficacy of the pendular mechanism, i.e., an improved recovery index (Z=0.97; P=0.004). INTERPRETATION: Our findings suggest that patients with ankle osteoarthritis adopt a walking strategy which improves recovery through the pendular mechanism. This may be a compensatory mechanism in order to economize energy which would counterbalance the energy waste due to low muscle efficiency. These modifications are proportional to the impaired ankle function. Our data provides a quantitative baseline to better understand the dynamics of ankle osteoarthritis and determine the individual role that lower limb joints play in the multiple chronic joint affections.