Quantitative assessment of ankle joint dynamics during recovery from injury

Our laboratory has developed efficient procedures which utilize system identification methods to determine the dynamic characteristics of the normal ankle. The objective of the present work was to assess the feasibility, validity, and sensitivity of using quantitative measures of joint dynamics to monitor the mechanical consequences of soft tissue injury and immobilization. Three patients recovering from fractures of the lower leg were examined repeatedly throughout their post-immobilization periods. Patients had no difficulty with the experimental procedures and measures of their ankle dynamics were qualitatively similar to those of normals. Stiffness was low in a region near the mid-range and increased sharply near the limits of movement. Repeated measures of joint dynamics showed progressive changes throughout the post-immobilization period which were consistent with the return of function. Consequently, the mid-range stiffness decreased while the width of the low-stiffness region increased. These results indicate that system identification methods should be considered for use in the clinical assessment of joint function.