Espiral AtlasTalocrural (ankle) joint
articulatio talocruralis
Study entry
Classification
Synovial hinge joint, between the distal ends of the tibia and fibula and the upper part of the talus. It is felt as a slight depression between the tendons on the front of the ankle, about 1 cm above the tip of the medial malleolus.
Surfaces
The tibia and fibula, with the inferior transverse tibiofibular ligament, form the malleolar mortise, into which the pulley-shaped trochlea of the talus fits. The inferior surface of the tibia forms the roof and transfers the weight to the talus; the medial malleolus articulates with the medial malleolar surface of the talus; the lateral malleolus, with the lateral one.
Capsule
Thin in front and behind, reinforced on each side by the collateral ligaments. Lateral: three separate ligaments, the anterior talofibular (weak, flat band, from the lateral malleolus to the neck of the talus), the posterior talofibular (thick, horizontal, from the malleolar fossa to the lateral tubercle of the talus) and the calcaneofibular (round cord, from the apex of the lateral malleolus to the lateral surface of the calcaneus). Medial (deltoid ligament): a strong fan from the medial malleolus to the talus, the calcaneus and the navicular, in four parts: tibionavicular, tibiocalcaneal, and anterior and posterior tibiotalar; it stabilizes the joint in eversion. The synovium may extend between the tibia and the fibula up to the interosseous tibiofibular ligament.
Movements
Dorsiflexion (muscles of the anterior compartment) and plantar flexion (muscles of the posterior compartment), about a transverse axis. Dorsiflexion is limited by the triceps surae and the collaterals. In plantar flexion the trochlea, narrower behind, sits more loosely in the mortise; this is when most ankle injuries happen, from sudden inversion of the foot.
Blood supply
Malleolar branches of the anterior tibial, posterior tibial and fibular arteries.
Innervation
Saphenous, tibial, sural and superficial and deep fibular nerves (the latter two, branches of the common fibular).
Clinical
Most injuries occur in plantar flexion, from sudden and unexpected inversion of the foot.
Source: cap. 7, «Articulaciones del miembro inferior»: articulación talocrural
Clinical correlation
Fractures of the fibula
The fibula usually breaks 2 to 6 cm above the tip of the lateral malleolus, often together with a fracture-dislocation of the ankle and a fracture of the tibia. When a person slips and the foot turns in exaggerated inversion, the ligaments of the ankle tear and the talus strikes the lateral malleolus and cuts it off. Fractures of both malleoli are common in soccer and basketball. It hurts because muscle attachments are torn, and walking gets worse because the fibula stabilizes the ankle.
Ankle sprain and fractures of the lateral malleolus
The ankle is the large joint most injured in the body, and the sprain (tearing of ligament fibers) is very common. It is almost always by inversion: the foot, in plantar flexion and bearing load, steps on uneven ground and turns inward. Sprain of the lateral collateral ligament is typical of sports with running and jumping; 70% to 80% of basketball players have had one. The lateral collateral suffers because it is much weaker than the medial and is the one that resists inversion. Its anterior talofibular part is the most vulnerable and the one that tears most, leaving the ankle unstable; the calcaneofibular may also tear.
Related clinical cases
- Fractures of the fibula
- Ankle sprain and fractures of the lateral malleolus