The PTFL is the strongest of the three lateral ankle ligaments, running nearly horizontally from the posterior fibula to the posterior talus. It is only torn in severe lateral ankle injuries — frank ankle dislocations — as it requires extreme plantarflexion and inversion beyond what ATFL and CFL failure alone allows. Its integrity provides the posterior constraint that prevents posterior dislocation of the talus from the mortise.
| Origin | Posterior lateral malleolus (digital fossa) |
|---|---|
| Insertion | Posterior talar process (lateral tubercle) |
| Actions | Strongest lateral ankle ligament; resists posterior talar displacement and extreme plantarflexion; only torn in complete ankle dislocations |
|---|
PTFL tears are rare in isolation and indicate a high-energy lateral ankle injury with probable concurrent deltoid and syndesmotic involvement. MRI confirms PTFL disruption as part of the assessment of severe ankle injuries. Its intact status is confirmed by the absence of posterior ankle instability on examination.
PTFL disruption as part of complete lateral ankle ligament failure in ankle dislocation requiring urgent reduction and ligamentous assessment.
