Ankle joint

Bones and articular surfaces

The joint is formed by the connection of the lower (distal) ends of the leg bones with the talus of the foot. In shape, this articulation resembles a mortise: the tibia and fibula embrace the trochlea of the talus (trochlea tali) on both sides.

The articular surfaces are distributed as follows:

• The superior articular surface of the trochlea (facies articularis superior) articulates with the inferior articular surface of the tibia.
• The lateral surfaces of the talar trochlea articulate with the inner surfaces of the medial and lateral malleoli.

An important role in the stability of this bony "mortise" is played by the distal tibiofibular syndesmosis. It is represented by a syndesmosis or joint — syndesmosis (articulatio) tibiofibularis. This connection is reinforced by strong anterior and posterior tibiofibular ligaments that prevent the leg bones from separating under load.

Joint capsule and ligamentous apparatus

The joint capsule attaches along the cartilaginous margin of the articular surfaces. On the anterior surface, it extends slightly forward, enclosing part of the neck of the talus. Anteriorly and posteriorly, the capsule is relatively thin, which ensures freedom of movement, but on the sides, it is powerfully reinforced by accessory ligaments running from the malleoli to the tarsal bones.

Medial collateral ligament (lig. collaterale mediale, or deltoid ligament — lig. deltoideum): Has the appearance of a broad plate whose shape resembles the Greek letter "delta". It securely fixes the inner side of the joint.

Lateral collateral ligament (lig. collaterale laterale): Consists of three separate bundles that fan out from the lateral malleolus:

1. The bundle running anteriorly — the anterior talofibular ligament (lig. talofibulare anterius).
2. The bundle running inferiorly — the calcaneofibular ligament (lig. calcaneofibulare).
3. The bundle running posteriorly — the posterior talofibular ligament (lig. talofibulare posterius).

Biomechanics and syntopy

In its structure, the ankle joint is classified as a typical hinge joint (ginglymus). The main axis of movement here is the frontal axis, passing strictly through the trochlea of the talus.

Around this axis, two main types of movement are possible:

• Dorsiflexion (or plantar extension): the foot is raised upward with the toes.
• Plantar flexion (or dorsal extension): the foot is lowered downward, extending in a straight line.

Important anatomical structures lie closely adjacent to the joint capsule. Anteriorly, the tendons of the foot extensor muscles pass. Posteriorly, the tendon of the flexor hallucis longus muscle (m. flexor hallucis longus) lies directly against the capsule.

Blood supply, lymph drainage, and innervation

Blood supply to the ankle joint is provided by a robust arterial network — the malleolar network (rete malleolare mediale et laterale). It is formed by branches of three major leg trunks:

• anterior tibial artery (a. tibialis anterior);
• posterior tibial artery (a. tibialis posterior);
• fibular artery (a. fibularis / peronea).

Venous outflow from the joint tissues drains into the deep veins of the leg of the same names. Lymphatic fluid drains via deep lymphatic vessels, heading upward to the popliteal lymph nodes (nodi poplitei).

Nerve supply to the joint is divided into zones:

• On the lateral side, the capsule is innervated by the n. suralis.
• On the medial (inner) side, branches are supplied by the n. saphenus.
• The anterior surface of the joint is supplied by the deep fibular nerve (n. peroneus profundus).

Briefly: answers to topical questions

Class and exam questions

What else to study on this topic

• Anatomy of the tibiofibular syndesmosis and its ligamentous apparatus
• Formation of the medial and lateral malleolar networks
• Topography of flexor and extensor tendons in the malleolar region
• Lymph drainage pathways from the foot to the popliteal lymph nodes

Other topics in the "Lower Limb" section

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