Ankle-Dorsiflexion Range of Motion and Landing Biomechanics (Original Research) (Report‪)‬

Anterior cruciate ligament (ACL) injury typically occurs during athletic participation via a noncontact mechanism involving planting, pivoting, or landing (or a combination of these). (1) A smaller amount of knee-flexion displacement, greater knee-valgus displacement, and greater vertical and posterior ground reaction forces during landing purportedly increase ACL loading and injury risk. (2-4) These biomechanical factors are interrelated, in that "stiff" landings characterized by an erect landing posture and less sagittal-plane displacement result in greater ground reaction forces than a more flexed landing posture. (5,6) Similarly, greater ground reaction forces are associated with greater knee-valgus displacement and moment. (2) The joints of the lower extremity function in concert in the sagittal plane to attenuate landing forces, such that greater motion at one joint is typically accompanied by greater motion at adjacent joints. (5,7,8) Although most authors studying ACL injury and landing biomechanics have focused on the knee and hip, considerably less attention has been devoted to the ankle. The ankle plantar flexors play a substantial role in the absorption of landing forces, (5,9) and a smaller amount of sagittal-plane ankle displacement (dorsiflexion) during landing results in greater peak landing forces. (5,8,10) Additionally, the sagittal-plane coupling of the lower extremity joints (5,7) suggests that less dorsiflexion displacement during landing is accompanied by less knee-flexion and hip-flexion displacement. This notion is supported by Kovacs et al, (8) who reported greater vertical ground reaction forces and smaller dorsiflexion, knee-flexion, and hip-flexion displacements during heel-to-toe landings than with forefoot-first landings. Hagins et al (11) restricted the available dorsiflexion range of motion (ROM) during landing by having participants land on an inclined surface and reported greater knee-valgus displacement and posterior ground reaction forces compared with landing on a flat surface that permitted full dorsiflexion displacement. Similarly, Sigward et al (12) demonstrated that individuals with less passive dorsiflexion ROM demonstrated greater knee-valgus excursion during landing. Furthermore, Bell et al (13) noted that medial knee displacement (valgus) during a controlled squatting task was diminished when the available dorsiflexion ROM was increased by placing a wedge under the calcaneus, indicating that dorsiflexion ROM influences frontal-plane knee motion. In combination, these results suggest that restricted dorsiflexion ROM may increase ACL loading and injury risk via association with less knee-flexion displacement, greater knee-valgus displacement, and greater ground reaction forces during landing.