Posterior tibiofibular ligament

The posterior tibiofibular ligament (Posterior inferior tibiofibular ligament; PITFL) stabilizes the distal tibiofibular syndesmosis at the ankle. This ligament extends from the posterior aspect of the distal tibia to the posterior aspect of the distal fibula, forming a key component of the syndesmotic complex that maintains the integrity of the ankle mortise and resists posterior and rotational displacement of the fibula relative to the tibia.

The PITFL consists of superficial and deep components. The deep component, sometimes called the transverse ligament (inferior transverse tibiofibular ligament)*, is particularly important for syndesmotic stability and is closely associated with the posterior intermalleolar ligament. The superficial PITFL has a broad tibial insertion, which is larger than the average size of posterior malleolar fracture fragments, indicating that ligamentous injury is necessary for posterior syndesmotic instability in the setting of such fractures.

Biomechanically, the PITFL is stronger than the anterior tibiofibular ligament and plays a critical role in constraining the ankle, especially against posterior translation and external rotation forces.

*For some sources, including Terminologia Anatomica 2, the "inferior transverse tibiofibular ligament" is a distinct anatomical structure from the posterior tibiofibular ligament, located at the distal tibiofibular syndesmosis, forming part of the posterior aspect of the ankle joint. It originates just below the posterior inferior tibiofibular ligament and extends transversely from the posterior edge of the tibia to the posterior margin of the lateral malleolus of the fibula. This ligament is variably present, with anatomical studies identifying it in approximately 70% of specimens, and its dimensions and shape can vary depending on the attachment points.