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+/-8.1 kg; height, 171.9+/-9.6 cm) and healthy controls (n=16; 7 men, 9 women; age, 20.4+/-1.7y; mass, 76.9+/-11.1 kg; height, 176.5+/-11.1 cm) 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.