Ankle-Dorsiflexion Range of Motion and Landing Biomechanics

Chun-Man Fong, LAT, ATC; J. Troy Blackburn, PhD, ATC; Marc F. Norcross, MA, ATC; Melanie McGrath, PhD, ATC; Darin A. Padua, PhD, ATC

Anterior Cruciate Ligament (ACL) injuries account for a large portion of athletic knee injuries. Although the ACL can be repaired arthroscopically and some patients can resume sporting activities without surgery, this injury has been reported to lead to symptomatic osteoarthritis within a few years of the injury. Therefore, preventative strategies to reduce the incidence of ACL injury are exceptionally important at preserving the integrity of the knee joint. ACL ruptures often occur during landing or jump-landing motions when the athlete assumes a dynamic valgus position of the knee joint. Inability to absorb the shock during landing (by flexing the knee) can increase this abnormal valgus motion and also increase the rate and magnitude of the ground reaction force. One limiting factor in knee flexion and shock absorption during landing is ankle dorsiflexion range of motion. It has been suggested that reduced ankle dorsiflexion is related to reduced knee flexion during landing, although no study has evaluated the relationship between goniometric measures of ankle motion and landing biomechanics. In other words, we don’t know if patients with less passive dorsiflexion will land with a greater loading rate and less knee flexion which was the objective of the study. Thirty-five healthy and physically active volunteers were tested in the descriptive laboratory study. Passive dorsiflexion was measured with the knee in an extended and semi-flexed position and this value was compared to knee flexion, knee valgus, vertical ground reaction force and posterior ground reaction force upon landing from a 30 cm height using correlational analysis. The authors found that reduced dorsiflexion range of motion was associated with reduced knee flexion displacement during landing and greater ground reaction forces, potentially setting the stage for an ACL injury.

This is an important finding and these authors were the first to report a direct correlation between passive ankle motion and landing mechanics that are linked to ACL injury. Ankle dorsiflexion can be improved by a variety of stretching techniques, so this may be an easy way to reduce the chance of ACL injury in patients with reduced ankle motion. This paper sets the stage for future research. It would be ideal if future researchers evaluated if ACL injuries are more prevalent in athletes with reduced dorsiflexion or if simple stretching programs can reduce the incidence of ACL injury in high risk athletes. Although more research is required to answer these important clinical questions, the fact that “the foot bone is connected to knee bone” lets us know that we may need to look beyond just the knee when we are trying to reduce the chance of ACL injuries.

Written by Joseph Zeni, Jr PT PhD
Reviewed by Stephen Thomas, PhD ATC