Abnormal viscoelastic behaviour of passive ankle joint movement in diabetic patients: an early or a late complication?

Aims/hypothesis: The goal of the present study was to compare the range of motion and both the viscous and elastic components of passive ankle joint movement in short- and long-term diabetic patients with that of a control population. Methods: Thirty-four diabetic patients and 16 control subjects entered into the study. Patients with a history of over 15 years of diabetes were considered as a long-term diabetic group. In order to quantify the passive ankle joint movement, a device was designed to measure the dorsi- and plantar-flexion angle and the net moment at the ankle. Elastic behaviour was examined as the separate slope of regression lines (stiffness) of plantar and dorsal components in the loading moment-angle curve. It was also examined as the slope of the regression line in the final 10% of each component. Hysteresis, a characteristic of viscoelastic materials that indicates loss of energy during unloading, was corrected for range of motion and used to examine viscous behaviour of the ankle joint. Results: Total and plantar ranges of motion were significantly lower in long-term diabetic patients than in short-term diabetic and control groups (p < 0.05). Plantar-flexion stiffness was significantly lower in short-term diabetic patients than in control subjects and long-term diabetic groups (p < 0.05). Corrected hysteresis was significantly higher in long-term diabetic than in short-term diabetic and control (p < 0.05) groups in the dorsal range of motion. Conclusions: This study shows that both decreased plantar and total ankle joint ranges of motion, and increased viscous component of passive ankle joint movement are among the late complications of diabetes.