![]() Because the CFL maintains a parallel relationship to the orientation of the functional axis of the subtalar joint throughout the range of talocrural joint motion, rotation of the dorsiflexed foot around a non-functional longitudinal axis, which induces lateral tilt of the talus, is the most likely mechanism of CFL disruption.įigure 2. Immediately after the ATFL is damaged by a combination of plantar flexion and inversion, a combination of reflexive hip flexion, knee flexion, and ankle dorsiflexion may make the CFL vulnerable to continuation of inward displacement of the sole of the foot. 7 This suggests that a two-stage sprain mechanism might explain the combination of ATFL and CFL rupture. Sudden inversion of the foot has been shown to elicit a reflexive postural response that lowers the body’s center of mass, which momentarily reduces the magnitude of the vertical ground reaction force acting on the ankle. The ATFL is most vulnerable to injury when the foot is in a position of plantar flexion, but the CFL is most vulnerable in a position of dorsiflexion. In many cases, rupture of the ATFL is associated with damage of the calcaneo-fibular ligament (CFL). ![]() In addition to the PTTL damage, the articular cartilage on the anteromedial margin of ankle joint can be damaged by forceful impact sometimes referred to as a “kissing” lesion (Figure 3). Because foot inversion can damage structures on the medial aspect of the ankle, the term “lateral ankle sprain” is often an incomplete designation for the pathology that results. Located on the posteromedial aspect of the ankle joint, the PTTL is the deep posterior component of the deltoid ligament (Figure 2). After the ATFL ruptures, the primary remaining restraint to further internal rotation of the talus is the posterior tibio-talar ligament (PTTL). ![]() Relative to the externally rotating tibio-fibular mortise, the talus internally rotates, and the anterior talo-fibular ligament (ATFL) is torn by excessive displacement of the bones in opposite directions (Figure 1). Reprinted with permission from reference 19.Ĭlosed-chain subtalar joint inversion induces external rotation of the tibio-fibular ankle mortise (and vice-versa). Simultaneous internal rotation of talus and external rotation of the tibia and fibula, which is primarily restrained by the ATFL. Two sets of articulations between the talus and the calcaneus form the subtalar joint (lower ankle joint), which rotates around a functional axis that has an approximate orientation of 45° in the sagittal plane (i.e, with the talocrural joint in a neutral position).įigure 1. When the ankle ligaments are intact, the functional axis of talocrural joint motion has a relatively transverse orientation that is aligned with the distal tips of the tibial and fibular malleoli. ![]() Its superior, medial, and lateral articular surfaces are encased within a socket (the tibio-fibular mortise), which forms the talocrural joint (upper ankle joint). 5 The key component of the ankle is the talus, which functions in a manner somewhat similar to that of a ball-bearing. The widely-used term “ankle joint” suggests the existence of a single joint between the leg and foot segments, which does not accurately represent the complex structure and integrated function of two distinct joints that both contribute to ankle motion. Inadequate treatment can result in suboptimal healing of damaged ligaments, which leads to recurrent traumatic episodes (i.e., chronic ankle instability) and progressive arthritic degeneration. Foot inversion (i.e., inward turning of the sole) is always a component of the injury mechanism that damages the lateral ankle ligaments, but numerous factors influence the nature and severity of the pathology that may result from the traumatic event. The lateral ankle sprain is the most common musculoskeletal injury associated with physical activity, but is often dismissed as a relatively trivial problem that is not expected to cause any long-term disability. Maximal protection of multiple ankle ligaments following a sprain requires a taping technique or brace that provides restraint of rotary talocrural and subtalar joint displacements within the transverse plane as well as restraint of inward hindfoot motion within the frontal plane. ![]()
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