A hinged joint capable of moving the foot towards and away from the body and in an up and down fashion.

The joint is actually made up of two joints: the subtalar joint, and the true ankle joint.

The true ankle joint is responsible for up and down motion of the foot.

The true ankle joint is formed by the distal tibia, fibula and talus bones.

The distal tibia forms the medial aspect of the joint, while the distal tibia forms the lateral ankle.

The second part of the ankle, the subtalar joint, consists of the talus on top and calcaneus on the bottom.

The joint connection between the tibia and the talus bears more weight than between the smaller fibula and the talus.

The talus has three facets and is wider anteriorly.

With dorsiflexion of the foot, the wider part of the superior talus moves into the articulating surfaces of the tibia and fibula.

The subtalar joint allows side to side motion of the foot.

The lateral bony aspects of the ankle, the malleoli, provide stability of the joint when weight bearing.

The lateral collateral ligaments attached to the lateral malleolus, and the medial collateral ligaments attached to the medial malleolus, provide stability of the joint.

The joint is surrounded by a fibrous joint capsule.

The bones in these joints are covered by articular cartilage.

The major ligaments of the ankle are: the anterior tibiofibular ligament connecting the tibia to the fibula, the lateral collateral ligaments, which attach the fibula to the calcaneus and gives the ankle lateral stability; and, on the medial side of the ankle, the deltoid ligaments, which connect the tibia to the talus and calcaneus and provide medial stability.

The ankle joint is bound by the strong deltoid ligament and three lateral ligaments: the anterior talofibular ligament, the posterior talofibular ligament, and the calcaneofibular ligament.

The joint is most stable in dorsiflexion and a sprained ankle is more likely to occur when the foot is plantar flexed.

The Achilles tendon passes behind the ankle and attaches to the heel of the foot.

The posterior tibial tendon passes behind the medial malleolus while the peroneal tendon passes behind the lateral malleolus.

The ankle allows foot movement to approximately 45 degree position of plantar flexion to a 20 degree dorsiflexed position.

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