THE INFLUENCE OF HEEL HEIGHT ON SAGITTAL PLANE KNEE KINEMATICS DURING LANDING TASKS IN RECREATIONALLY ACTIVE AND ATHLETIC COLLEGIATE FEMALES

Purpose: To determine if heel height alters sagittal plane knee kinematics when landing from a forward hop or drop landing. Background: Knee angles close to extension during landing are theorized to increase ACL injury risk in female athletes. Methods: Fifty collegiate females performed two single-limb landing tasks while wearing heel lifts of three different sizes (0, 12 & 24 mm) attached to the bottom of a sneaker. Using an electrogoniometer, sagittal plane kinematics (initial contact [KA(IC)], peak flexion [KA(Peak)], and rate of excursion [RE]) were examined. Repeated measures ANOVAs were used to determine the influence of heel height on the dependent measures. Results: Forward hop task-KA(IC) with 0 mm, 12 mm, and 24 mm lifts were 8.8 degrees +/- 6.5, 9.3 degrees +/- 5.8 and 11.2 degrees +/- 7.0, respectively. Significant differences were noted between 0 and 24 mm lift (p<. 001) and 12 and 24 mm lifts (p=.003), but not between the 0 and 12 mm conditions (p=.423). KA Peak with 0 mm, 12 mm, and 24 mm lifts were 47.0 degrees +/- 10.9, 48.0 degrees +/- 10.3 and 48.8 degrees +/- 9.7, respectively. A significant difference was noted between 0 and 24 mm lift (p=. 004), but not between the 0 and 12 mm or 12 and 24 mm conditions (p=. 071 and p=. 282, respectively). The RE decreased significantly from 212 degrees/sec +/- 52 with the 12 mm lift to 195 degrees/sec +/- 55 with the 24 mm lift (p=. 004). RE did not differ from 0 to 12 or 0 to 24 mm lift conditions (p=. 351 and p=. 086, respectively). Jump-landing task-No significant differences were found in KA(IC) (p=. 531), KA(Peak) (p=. 741), or the RE (p=. 190) between any of the heel lift conditions. Conclusions: The addition of a 24 mm heel lift to the bottom of a sneaker significantly alters sagittal plane knee kinematics upon landing from a unilateral forward hop but not from a drop jump.