Ankle Anatomy: Ligaments & Tendons 2026 | DPM

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The Ankle Joint Complex

The ankle (talocrural joint) is a mortise-and-tenon joint formed by three bones: the tibia (medial malleolus and tibial plafond), the fibula (lateral malleolus), and the talus. The talus fits precisely into the mortise created by the tibia and fibula — the width of the mortise is maintained by the syndesmotic ligaments above.

The tibiotalar joint allows primarily dorsiflexion (toes up) and plantarflexion (toes down) motion. The subtalar joint (talocalcaneal) below contributes inversion and eversion. True ankle ‘rolling’ involves both the tibiotalar and subtalar joints.

The articular cartilage of the tibial plafond and talar dome is remarkably thin (1–3mm) but bears loads of 5–8x body weight during running. Damage to this cartilage (osteochondral lesions) is a significant source of chronic ankle pain after sprains.

Lateral Ankle Ligaments

Three ligaments form the lateral complex, all originating from the fibula. The anterior talofibular ligament (ATFL) runs from the anterior fibula to the talar neck — it is the most commonly injured ligament in ankle sprains, damaged in 90% of lateral sprains. It resists anterior drawer of the talus and is under maximum tension in plantarflexion (the vulnerable position for ankle sprains).

The calcaneofibular ligament (CFL) runs vertically from the fibula to the lateral calcaneus, resisting inversion in neutral ankle position. The posterior talofibular ligament (PTFL) is the strongest lateral ligament and is only injured in severe dislocations.

Chronic ATFL laxity after inadequately rehabilitated sprains leads to chronic ankle instability — a condition affecting up to 40% of ankle sprain patients. Diagnosis involves stress X-rays and MRI. Surgical reconstruction (Broström-Gould procedure) restores stability when conservative management fails.

Medial and Syndesmotic Ligaments

The deltoid ligament is a broad, powerful medial ligament complex that resists eversion and provides the primary medial stability. Because it is so strong, isolated deltoid sprains are less common than lateral sprains — when the deltoid tears, it usually occurs with an associated fracture. The deltoid has superficial and deep layers; complete deltoid disruption is a serious injury.

The syndesmotic ligaments (anterior and posterior tibiofibular ligaments, interosseous membrane) bind the tibia and fibula together, maintaining mortise width. High ankle sprains — syndesmotic injuries — occur when the foot is externally rotated under load. They are more painful, slower to heal, and more debilitating than lateral sprains. Unstable syndesmotic injuries require surgical fixation with suture button or screw.

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