Ankle

In simpler terms, the ankle is the area where the foot and the leg meet. It consists of three joints: the ankle joint or talocrural joint, the subtalar joint, and the distal tibiofibular joint. In anatomical and medical contexts, it specifically refers to the ankle joint.

Bony framework:

• The ankle joint (a.k.a. talocrural joint) is formed by the upper surface of the talus and the lower ends of the tibia and fibula, including the medial and lateral malleoli.

• It is a hinge-type synovial joint, allowing two movements: plantar flexion (foot down) and dorsiflexion (foot up).

Capsule and ligaments:

The capsule of the ankle joint is lax anteroposteriorly and is reinforced by ligaments:

• Medial (deltoid) ligament: Extending from the medial malleolus to the medial tarsal bones.

• Lateral ligament: Comprising three separate ligaments extending from the lateral malleolus to the lateral tarsal bones. The lateral ligament is weaker than the medial (deltoid) ligament, making it more susceptible to injury in ankle sprains.

Due to the wedge shaped articular surface (wider anteriorly), it fits well into the tibiofibular socket between the two malleoli when dorsiflexed. Consequently, the ankle joint is more stable in dorsiflexion than in plantar flexion.

Muscles:

Numerous long tendons of leg muscles pass over the ankle joint, enabling movements like plantar and dorsiflexion, inversion, and eversion. These tendons are held close to the underlying bones by thickened deep fascia called retinacula.

• Dorsiflexors and plantar flexors of the ankle joint: Muscles of the anterior leg (tibialis anterior, extensor hallucis longus, extensor digitorum longus, peroneus tertius) pass in front of the ankle joint and cause dorsiflexion, while posterior leg muscles pass behind the ankle joint and cause plantar flexion of foot (calf muscles, tibialis posterior, flexor hallucis longus, flexor digitorum longus).

• Evertors of the ankle joint: Lateral leg muscles sling around the lateral malleolus. Peroneus brevis inserts into base of the 5th metatarsal and causes eversion, as does peroneus longus. The latter passes under the sole to reach the medial side of foot, enabling to cause plantar flexion as well. Peroneus tertius also contributes to eversion.

• Invertors of the ankle joint: Medial muscles (tibialis anterior and tibialis posterior) acts as invertors of the foot.

Ankle sprain:

An ankle sprain occurs when the ligaments of the ankle joint are partially or completely torn. It usually happens when a weight-bearing foot is excessively inverted in a plantarflexed position. The lateral ligament is more vulnerable to injury due to its relative weakness compared to the medial (deltoid) ligament, which resists inversion. Eversion sprains are less common since the fibula tends to prevent excessive eversion of the ankle.