The deltoid ligament is a triangular, multilayered medial ankle ligament far stronger than the lateral ankle ligaments, which explains why medial ankle sprains are uncommon but lateral sprains are the most common ligamentous injury in sport. It has a superficial layer (tibionavicular, tibiocalcaneal, posterior superficial tibiotalar) and a deep layer (anterior and posterior tibiotalar). Its strength means that eversion ankle injuries more commonly produce medial malleolus fractures than isolated deltoid tears.
| Origin | Medial malleolus (anterior and posterior colliculi) |
|---|---|
| Insertion | Navicular tuberosity (tibionavicular), sustentaculum tali (tibiocalcaneal), and medial talus (anterior and posterior tibiotalar) |
| Actions | Primary medial ankle stabiliser — resists eversion, abduction, and external rotation of the talus in the mortise |
|---|
Deltoid ligament incompetence produces medial ankle instability and a valgus hindfoot that is identified by increased medial clear space (greater than 4 mm) on stress radiographs. After ankle fracture fixation, a persistent medial clear space widening indicates an intact but insufficient deltoid that may require repair. Acute complete deltoid tears from ankle fracture-dislocations require surgical repair alongside the fracture fixation.
Medial ankle ligament disruption from severe eversion force or ankle fracture-dislocation producing medial ankle instability, requiring repair when associated with bimalleolar equivalent ankle fractures.
