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

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.

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.

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.

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.