The effect of limitation in ankle dorsiflexion on knee joint function. A pilot study.

BACKGROUND A restriction in ankle dorsiflexion is a common complication of ankle fractures. This kind of dysfunction, if severe, can significantly influence gait. A restriction in ankle dorsiflexion (forward movement of the shin relative to the foot) can cause, among others, hyperextension of the knee during the stance phase. The length of leading leg step is shortened and alternant walk downstairs is very difficult. The aim of this study was to examine the correlation between the range of dorsiflexion in the ankle joint and the range of extension (hyperextension) in the knee joint. MATERIAL AND METHODS The study enrolled 17 patients after ankle joint fractures treated conservatively or surgically. The extension ranges of motion in the ankle and knee joints were assessed by goniometry to compare these values in injured vs. healthy limbs. Non-parametric methods (the Wilcoxon signed-rank test) were used for the analysis. RESULTS The results showed limitation in ankle dorsiflexion in the fractured limb, which amounted to 4.40 vs. 16.00 in healthy limbs in all patients. This difference was statistically significant (p<0.001). There was also a significantly (p<0.001) greater range of knee hyperextension on the side of injury (5.00 vs. 1.90 in healthy limbs). CONCLUSIONS 1. Post-traumatic restriction of ankle dorsiflexion can cause knee joint overload. 2. Examinations of knee function during walking should be carried out in patients with trauma-related dysfunctions of the ankle joint in order to prevent secondary musculoskeletal abnormalities.