A comparison of three-dimensional lower extremity kinematics during running between excessive pronators and normals.

OBJECTIVE: The purpose of this research was to compare the three-dimensional kinematics of runners exhibiting excessive rearfoot pronation with those having normal rearfoot pronation. DESIGN: The study design was a comparative investigation of two types of running patterns. BACKGROUND: Excessive rearfoot pronation is often linked with overuse injuries of the lower extremity. However, the literature is void of papers describing the rearfoot motion of runners presenting with excessive rearfoot pronation. Many knee-related injuries in runners are associated with increased rearfoot pronation; however, knee mechanics in this population of runners have yet to be studied. Finally, three-dimensional studies are needed to describe joint motion fully during running and these are also lacking. METHODS: Eighteen subjects (nine excessive pronators -- PRs; nine normals -- NLs) were studied during treadmill running at 3.35 m/s. Retroreflective markers were placed on the foot, shank and thigh segments and recorded with four 200 Hz video cameras. Three-dimensional kinematics were computed. RESULTS: A downward shift of the eversion curve was seen in the PR group resulting in an everted position of the rearfoot at both footstrike and toe-off compared with an inverted posture seen in the NL group. The amount of toe-out was not significantly different between the two groups. At the knee, the PR group demonstrated significantly less adduction and significantly greater flexion than the NL. Mean peak velocities of the PR group were greater in all angular measures except knee adduction. However, only foot dorsiflexion and eversion and knee flexion velocities were significantly different. CONCLUSIONS: Kinematic differences were noted at both the rearfoot and the knee of the runners who exhibit excessive rearfoot pronation.