Transverse-plane mechanics at the knee and tibia in runners with and without a history of achilles tendonopathy.

STUDY DESIGN Retrospective cohort study. OBJECTIVES To determine if runners with a history of Achilles tendonopathy (AT) demonstrate a difference in transverse-plane motion and moments at the distal tibia and knee compared to runners without a history of AT. BACKGROUND One of the more prevalent overuse running injuries is AT. It has been hypothesized that prolonged pronation causes contradictory rotational forces acting on the AT. Conflicting joint motions may also accentuate the rotation of the tendon. This may further affect the opposing transverse-plane moments at the knee and distal tibia. METHODS AND MEASURES Eight runners with a history of AT and a noninjured control group consisting of 8 runners ran along a 20-m runway at a fixed speed. Biomechanical measurements were taken using a 6-camera motion analysis system and a force plate. Student t tests were employed to determine statistically significant differences (P </= .05) in transverse-plane motion and moment variables at the distal tibia and knee between groups. RESULTS The AT group showed less tibial external rotation moment (P = .01) and peak knee internal rotation (P = .05) compared to the control group. There was no difference in external rotation moment at the knee (P = .34) or peak tibial internal rotation (P = .44). CONCLUSION Runners with a previous history of AT exhibited less tibial external rotation moments during running. The lack of control in the transverse-plane at the distal tibia may be due to decreased function of the muscles primarily responsible for transverse-plane motion, resulting in greater strain on the AT in the transverse-plane. Designing an exercise program to strengthen lower leg muscles and improve distal tibial control in the transverse-plane may reduce the risk for developing AT or augment the rehabilitation of AT.