Ankle instability: evaluation of the lateral ligaments.

Bilateral ankle stress testing was performed on 25 subjects in a device which controlled position of the foot and the amount of force applied during the examination. Both inversion testing in the anteroposterior plane and anterior drawer testing in the lateral plane were performed in the same group of symptom-free patients. The reproducibility of the test was demonstrated. Previous history of injury, left vs. right handedness, side and anthropometric measurements did not affect the test. There was no difference in the inversion test between ankles tested in neutral and plantar flexion. In functionally normal ankles, the range of inversion "talar tilt" was 0 to 18 degrees while the maximum of anterior displacement on drawer testing was 3 mm. The effective stiffness of the anterior talofibular ligament was thus computed as 65 +/- 34 N/m. Anterior drawer testing appears to evaluate lateral ligamentous integrity of the ankle more critically than the talar tilt test.