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Ankle Joint


The ankle joint is a synovial uniaxial hinge joint. The ankle joint is formed by three bones: (i) Tibia, (ii) Fibula, (iii) Talus. The joint consists of a deep socket formed by the lower end of tibia; and fibula into which is fitted the upper part of the body of talus. The factors contributing to the stability of the ankle joint are:-

  1. Close interlocking of the articular surfaces.
    The shape of articular surfaces maintains the stability of the joint.
    1. Talus is wedge shaped, being wider anteriorly, the malleoli of tibia and fibula are oriented to fit this wedge.
    2. The posterior border of the lower end of tibia is prolonged down wards.
  2. Fibrous capsule
    1. The joint is covered by a thin fibrous capsule which is strengthened medially and laterally by the collateral ligaments.
  3. Medial collateral ligament (Deltoid ligament)
    It is a strong triangular band attached above to the tip, anterior and posterior margins of medial malleolus. It consists of superficial and deep parts.
    1. Superficial part has three bands :-
      1. Tibionavicular part: - Attached to navicular tuberosity and spring ligament.
      2. Tibiocalcaneal part:-Attached to sustentaculum tali of calcaneum.
      3. Posterior tibiotalar part:-Attached to medial tubercle and medial surface of talus.
    2. Deep part (anterior tibiotalar part) is attached to the anterior part of the medial surface of talus below the coma-shaped articular surface. Tendons of tibialis posterior and flexor digitorum longus cross this
  4. Lateral collateral ligament
    It consists of three distinct parts:-
    1. Anterior Talofibular Ligament: From anterior margin of lateral malleolus of fibula to lateral aspect of neck of talus.
    2. Posterior Talofibular Ligament: From the lower part of malleolar fossa of fibula to the lateral tubercle of the posterior process of talus.
    3. Calcaneofibular Ligament: It is a long rounded cord-like ligament extending from the tip of the lateral malleolus to a tubercle on the lateral surface of the calcaneum. This ligament is crossed by tendons of the peroneus longus and peroneus brevis.

  1. Syndesmotic ligaments
    1. These are (i) Anterior tibiofibular, (ii) Posterior tibiofibular, (iii) Inferior transverse ligament and (iv) Interosseous ligament.
  2. Tendons that cross the joint


Active movements permitted at ankle joint are dorsiflexion and plantar flexion. Dorsiflexion is the closed packed position with maximum congruence of the joint surfaces and ligaments tension. Thus talus fits snugly into the socket when foot is dorsi flexed and there are no chances of ankle dislocation in dorsiflexion. When foot is plantar flexed, talus is slightly loose and may allow slight lateral rotation with maximum chances of dislocation. Thus, Ankle is more stable in dorsiflexed position.


Principal muscles


Accessory muscles



Tibialis anterior

Extensor digitorum longus, Extensor hallucis longus, Peroneus tertius (Muscles of anterior compartment of leg)

Plantar flexion


Plantaris tibialis posterior, flexor hallucis longus, flexor digitorum longus (Muscles of posterior compartment of leg)

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