Sprained ankle

An ankle sprain usually occurs in inversion and is accompanied by an external ligament injury that affects the anterior bundle, and only in severe sprains the middle fibulocalcaneal bundle, which spawns both the tibiotarsal and the subtalian articulation. The sprain mechanism is favored by the attack of the step on the external side of the heel, therefore in supination. The FHL is responsible for this since the gait cycle is shifted in rotation which leads to exaggerated and prolonged pronation during propulsion; the shift continues thereafter with a sweeping effect in the oscillating phase followed by an exaggerated supination in the attack from the heel to the ground. Another contributing factor caused by the FHL is the blockage of the subtalar varus by the tendon cord of the FHL (Flexor Hallucis Longus). The joint thus loses its ability to adjust in varus-valgus, which is particularly useful on uneven ground or upon landing a jump. It is imperative to take this predisposition to sprain into account and attempt to correct it during rehabilitation by freeing the subtalar and the sliding of the FHL.

When sprains are repeated or instability sets in despite well-conducted conservative treatment, FHL tenolysis may be offered to stabilize the ankle. This minimally invasive measure is often more effective than a ligament reconstruction because it frees the subtalar at the same time and attenuates the supine attitude when the foot lands on the ground by resynchronizing the moments of passage internal-external rotation and vice-versa.