Mechanical Instability After an Acute Lateral Ankle Sprain

Mechanical instability after an acute lateral ankle sprain. Objective: To examine the natural recovery of mechanical laxity after an ankle sprain over an 8-week period. Design: Prospective cohort study. Setting: Biodynamics research laboratory. Participants: Subjects with an acute lateral ankle sprain (n = 16; 7 men, 9 women; age, 19.5 +/- 0.7y; mass, 64.6 +/- 8.1kg; height, 171.9 +/- 9.6cm) and healthy controls (n = 16; 7 men, 9 women; age, 20.4 +/- 1.7y; mass, 76.9 +/- 11.1kg; height, 176.5 +/- 11.1cm) participated. Interventions: Not applicable. Main Outcome Measures: Subjects with acute ankle sprains were tested 3 days after injury and again 8 weeks later. Anterior and posterior displacement (mm) and inversion and eversion rotation (degrees) were measured with an instrumented arthrometer. For each dependent variable, a 2 X 2 X 2 repeated-measures multivariate analysis of variance was performed. Results: A significant interaction was found between group, time, and side for anterior translation (F=4.24, P=.05). There were also significant main effects for group. There was significantly more anterior displacement at day 3 (F=19.52, P=.001) and at week 8 (F=8.45, P=.010) in the injured group compared with the healthy group. There was also significantly more inversion rotation at day 3 (F=2.70, P=.002) and at week 8 (F=5.4, P=.033) in the injured group compared with the healthy group. Conclusions: The lack of significant differences in mechanical laxity over an 8-week period suggests that natural recovery of laxity takes longer than 8 weeks. Further research needs to be conducted to examine how long this laxity persists and the role ankle rehabilitation plays in mechanical stability restoration.