Posterior tibiofibular ligament

At a glance

English

Posterior tibiofibular ligament

Latin (TA2)

Ligamentum tibiofibulare posterius

System

Ligament

Region

Foot

Side

Paired, left and right

About the posterior tibiofibular ligament

The posterior tibiofibular ligament, also called the posterior inferior tibiofibular ligament, is one of the bands that hold the lower ends of the two leg bones together. Just above the ankle, the fibula sits in a notch on the outer side of the tibia, and the two are joined by a fibrous union, the distal tibiofibular syndesmosis. This ligament strengthens the back of that union. Its fibres run obliquely downwards and outwards from the posterior border of the tibia, near the fibular notch, to the back of the lateral malleolus.

It is the posterior counterpart of the anterior tibiofibular ligament, which crosses the front of the syndesmosis in the same way and is somewhat larger. Between the two, the interosseous ligament fills the gap between the bones and continues upwards as the interosseous membrane of the leg. Below the posterior ligament, and partly blended with its deep part, lies the transverse tibiofibular ligament, which dips below the edge of the bones and deepens the back of the socket for the talus.

Together these bands bind the tibia and fibula into the ankle mortise, the deep socket that grips the dome of the talus. When the foot is pulled upwards, the wider front of the talus wedges into the mortise and the fibula is pushed slightly outwards; the syndesmotic ligaments allow this small movement while keeping the two bones from separating.

A high ankle sprain is an injury of the syndesmosis, usually caused by forced outward rotation of the foot. It heals more slowly than an ordinary lateral sprain. In some ankle fractures the posterior ligament stays intact but pulls off a fragment of the back of the tibia, the posterior malleolus. Widening of the mortise on radiographs suggests the syndesmosis has failed.

Attachments and function

Attaches from

The posterior border of the lower tibia, next to the fibular notch.

Attaches to

The posterior aspect of the lateral malleolus of the fibula.

Function

Binds the fibula to the back of the tibia, stabilises the ankle mortise and limits separation of the two bones while allowing slight fibular movement.

Nerve supply

Articular branches of the tibial and deep fibular nerves.

Blood supply

Branches of the fibular (peroneal) artery, including its perforating branch.