Subtalar jointThe subtalar joint (talocalcaneal joint) is traditionally described as the articulation formed between two tarsal bones; the talus and calcaneus. In the literature, this joint is also referred to as the anatomical subtalar joint or subtalar joint proper.
However, in clinical practice, the subtalar joint is considered as a functional unit consisting of the anatomical subtalar (posterior) and talocalcaneonavicular (anterior) joints. In the middle of this functional unit is the conical interosseous tunnel consisting of the tarsal canal and tarsal sinus.
The anatomical subtalar joint is a single synovial articulation formed between the posterior calcaneal articular facet of the talus and the convex posterior articular facet of the calcaneus. These bones are held together by the fibrous capsule, medial talocalcaneal, lateral talocalcaneal, interosseous talocalcaneal and cervical ligaments.
Two principal movements occur in this joint; inversion and eversion. These movements are affected by several adjacent joints, ligaments and periarticular tendinous tissue.
This article will discuss the anatomy and function of the talocalcaneal joint.
|Type||Plane synovial joint; three degrees of freedom|
|Articular surfaces||Posterior calcaneal facet on the posterior part of the inferior surface of the talus;
Posterior facet on the superior surface of the calcaneus
|Ligaments||Medial, lateral and posterior talocalcaneal ligaments, interosseous talocalcaneal and cervical ligaments|
|Innervation||Plantar aspect - medial or lateral plantar nerve
Dorsal aspect - deep fibular nerve
|Blood supply||Posterior tibial artery, fibular artery|
|Movements||Inversion and eversion (gliding and rotation)|
- Articular surfaces
- Ligaments and joint capsule
- Blood supply
- Muscles acting on the subtalar joint
- Clinical relations
The anatomical subtalar joint is a synovial articulation between the talus and calcaneus. It consists of two articular facets lined with the hyaline cartilage.
The articular surfaces that comprise this joint involve the concave posterior calcaneal facet on the inferior surface of the talus and the convex posterior talar articular surface on the superior aspect of the calcaneus.
Learn more about the general features of the synovial joints by exploring articles, diagrams, videos and quizzes.
Ligaments and joint capsule
The subtalar joint has one loose joint capsule that envelops the whole joint. Like in other synovial joints, the joint capsule is lined with a synovial membrane. The lateral, medial and posterior thickenings of the joint capsule are the main ligaments that participate in movements of this joint. The subtalar joint capsule attaches to the edges of the articular surfaces as well as to the floor and roof of the tarsal sinus. The tarsal sinus is a narrow passageway located immediately anterior to the subtalar joint, between the talus and calcaneus.
Inside the tarsal sinus, the joint capsules of the subtalar and talocalcaneonavicular joints meet and form the talocalcaneal interosseous ligament.
The materal talocalcaneal ligament is a flat fibrous band that spans obliquely between the lateral talar process to the lateral calcaneal surface and calcaneofibular ligament. It lies deep to the calcaneofibular ligament.
The medial talocalcaneal ligament spans between the medial aspects of talar tubercle and calcaneus and the posterior aspect of sustentaculum tali. Some of its distal biers blend with the medial deltoid ligament of the ankle joint.
The posterior talocalcaneal ligament is a short band of fibrous tissue that spans from the posterolateral tubercle of the talus to the superomedial aspect of the calcaneus.
The interosseous talocalcaneal ligament is composed of two short and broad fibrous bands located in the tarsal sinus. The deep extension of the inferior extensor retinaculum is situated between these bands of the interosseous ligament. Occupying the central position between the talocalcaneal and talocalcaneonavicular joints, this ligament is associated with the functions of both joints. The primary role of this ligament in the subtalar joint is maintaining stability both at rest and during active movements. Being attached to the talar sulcus and calcaneal sulcus, the interosseous talocalcaneal ligament is taut in eversion of the foot, limiting its movement.
The cervical ligament is located lateral to the interosseous ligament and the tarsal sinus. It extends from the superior calcaneal surface to the inferolateral tubercle of the talar neck. This ligament is also taut in eversion.
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The plantar aspect of the subtalar joint is innervated by the medial or lateral plantar nerves, while the dorsal aspect receives its innervation from the deep fibular nerve.
Arterial supply for the subtalar joint comes from two arteries;
The movements that occur at the subtalar joint are gliding and rotation.The combination of these movements result in eversion and inversion; they are considered to be the primary movements in the subtalar joint. They are always accompanied by movements in the talocalcaneonavicular and calcaneocuboid joints which is why these three joints are considered to be one functional unit of the foot. Inversion and eversion can be considered to occur around a single axis that runs anteriorly and superomedially from the posterolateral tubercle of calcaneus to the superomedial aspect of the neck of talus. The range of motion (ROM) in this joint varies across authors; the ROM in inversion ranges from 25° to 30°, while in eversion it ranges from 5° to 10°.
Inversion is the movement in which the sole of the foot faces towards the midline, while the lateral border of the foot is directed inferiorly. Inversion is a combination of the adduction and supination of the foot, followed by the plantarflexion that occurs at the ankle joint. It is important to note that abduction and supination in the subtalar joint always occur together.
In inversion, the navicular and cuboid bones rotate around the anteroposterior axis (supination) and glide medially (abduction), pulling the calcaneus anteriorly. These movements of tarsal bones result in elevation of the medial longitudinal arch and inversion of the foot.
In contrast to inversion, eversion is the movement in which the sole of the foot faces laterally while the medial border of the foot is directed inferiorly. Eversion occurs when the abduction and pronation of the foot are combined with dorsiflexion at the ankle joint. Similar to adduction and supination, abduction and pronation are never functionally separate movements, and thus always accompany each other.
In eversion, the navicular and cuboid bones move laterally (abduction) and rotate medially around the same anteroposterior axis (pronation). While rotating the cuboid bone pushes the calcaneus posteriorly. These bony movements result in turning the sole of the foot outward.
The closed packed position of the subtalar joint is supination. The capsular pattern has a limited ROM defined in varus and valgus.
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Muscles acting on the subtalar joint
- Inversion in the subtalar joint is primarily produced by tibialis anterior and tibialis posterior, with assistance from extensor hallucis longus, flexor hallucis longus and flexor digitorum longus.
- Eversion is mainly produced by fibularis longus, fibularis brevis and fibularis tertius with assistance from the extrinsic muscles that extend the toes (extensor digitorum longus and extensor hallucis longus).
Sinus tarsi syndrome
Sinus tarsi syndrome is a painful clinical condition caused by excessive motions of the subtalar joint. It is typically seen in dancers, runners, volleyball and basketball players. The persistent anterolateral ankle discomfort that occurs in athletes can result in subtalar joint synovitis and infiltration of fibrous tissue into the sinus tarsi space. The diagnosis is usually established by the physical examination that reveals a localized ankle discomfort to the sinus tarsi space and feelings of instability with pronation and supination movements of the subtalar joint. In treatment, physical therapy in combination with anti-inflammatory medication is usually efficient.