Tear of the lateral (talofibular) ligaments of the ankle

Definition:

A partial or complete discontinuity in the connective tissue fibre matrix comprising the lateral ligaments of the ankle.

Causes:

There are numerous factors leading to the increased vulnerability if the lateral (talofibular) ligaments as opposed to their medial counterparts. Firstly: the fibula projects further distally than the tibia, thereby favouring ankle inversion, secondly: the biomechanics of the ankle promote inversion during toeing-off, and thirdly: the lateral ankle ligaments are weaker then the medial ones. Most lateral ligament tears of the ankle are traumatic and are the result of inversion sprains when the foot is slightly plantar flexed, resulting in a loose-pack position at the ankle. This type of injury can occur when landing on someone else’s foot, such as in basketball.

Examination:

The patient will usually present with pain over the lateral aspect of the ankle. Lateral ankle ligamentous sprains are sub-divided into three grades.

Grade I: mild tear of the involved ligament(s), associated with slight pain, and oedema. The stability of the ankle is not compromised and the patient is usually able to weight-bare.

Grade II the tear is more extensive, and associated with more severe ecchymoses, and oedema. Weight-baring is usually painful, but can be achieved.

Grade III is a complete tear of the affected ligament(s), with severe oedema and ecchymoses. Ankle stability is severely compromised, and weight-bareing is not usually achievable.

Orthopaedic tests for lateral talofibular ligament sprain.

Drawer’s foot sign: with the patient supine, grasp the patient’s foot and invert it. Excessive motion with pain can be interpreted as a positive.