In
human anatomy, the subtalar joint, also known as the
talocalcaneal joint, is a
joint
A joint or articulation (or articular surface) is the connection made between bones, ossicles, or other hard structures in the body which link an animal's skeletal system into a functional whole.Saladin, Ken. Anatomy & Physiology. 7th ed. McGraw- ...
of the
foot. It occurs at the meeting point of the
talus and the
calcaneus.
The joint is classed structurally as a
synovial joint,
and functionally as a
plane joint.
Structure
The talus is oriented slightly obliquely on the anterior surface of the calcaneus.
There are three points of articulation between the two bones: two anteriorly and one posteriorly. The three articulations are known as facets, and they are the posterior, middle and anterior facets.
* At the ''anterior and middle talocalcaneal articulation'',
convex
Convex or convexity may refer to:
Science and technology
* Convex lens, in optics
Mathematics
* Convex set, containing the whole line segment that joins points
** Convex polygon, a polygon which encloses a convex set of points
** Convex polytop ...
areas of the talus fits on to
concave
Concave or concavity may refer to:
Science and technology
* Concave lens
* Concave mirror
Mathematics
* Concave function, the negative of a convex function
* Concave polygon, a polygon which is not convex
* Concave set
* The concavity of a ...
surfaces of the calcaneus.
* The ''posterior talocalcaneal articulation'' is formed by a concave surface of the talus and a convex surface of the calcaneus.
The
sustentaculum tali forms the floor of middle facet, and the anterior facet articulates with the head of the talus, and sits lateral and congruent to the middle facet. In some people the middle and anterior facets are joined giving just one articulation. The posterior facet is the largest of the three, and separated from the others by the tarsal canal.
Ligaments and membranes
The main
ligament of the joint is the
interosseous talocalcaneal ligament
The interosseous talocalcaneal ligament forms the chief bond of union between the talus and calcaneus.
It is a portion of the united capsules of the talocalcaneonavicular and the talocalcaneal joints, and consists of two partially united layers ...
, a thick, strong band of two partially joined fibers that bind the talus and calcaneus. It runs through the
sinus tarsi, a canal between the articulations of the two bones.
There are four additional ligaments that form weaker connections
between the talus and calcaneus.
* The
anterior talocalcaneal ligament (or anterior interosseous ligament) attaches at the neck of the talus on the front and lateral surfaces to the superior calcaneus.
* The short band of the
posterior talocalcaneal ligament extends from the lateral tubercle of the talus to the upper medial calcaneus.
* The short, strong
lateral talocalcaneal ligament connects from the lateral talus under the fibular facet to the lateral calcaneus, and runs parallel to the
calcaneofibular ligament
The calcaneofibular ligament is a narrow, rounded cord, running from the tip of the lateral malleolus of the fibula downward and slightly backward to a tubercle on the lateral surface of the calcaneus. It is part of the lateral collateral ligament ...
.
* The
medial talocalcaneal ligament extends from the medial tubercle of the talus to the
sustentaculum tali on the medial surface of the calcaneus.
A
synovial membrane lines the capsule of the joint, and the joint
is wrapped in a capsule of short fibers that are continuous with the
talocalcaneonavicular and calcaneocuboid joints of the foot.
Function
The joint allows
inversion and
eversion of the foot, but plays minimal role in
dorsiflexion
Motion, the process of movement, is described using specific anatomical terms. Motion includes movement of organs, joints, limbs, and specific sections of the body. The terminology used describes this motion according to its direction relativ ...
or
plantarflexion
Motion, the process of movement, is described using specific anatomical terms. Motion includes movement of organs, joints, limbs, and specific sections of the body. The terminology used describes this motion according to its direction relativ ...
of the foot. The centre of rotation of the subtalar joint is thought to be in the region of the middle facet.
It is considered a plane synovial joint, also commonly referred to as a
gliding joint.
It acts as a hinge connecting the talus and calcaneus. There is extensive variation in the inclination from horizontal.
The subtalar joint can also be considered a combination of the anatomic subtalar joint discussed above, and also the talocalcaneal part of the
talocalcaneonavicular joint. This is the more common view of the subtalar joint when discussing its movement. When both of these articulations are accounted together, it allows for
pronation and
supination of the midfoot to occur.
Pathology
The subtalar joint is particularly susceptible to
arthritis, especially when it has previously been affected by
sprains or fractures such as those of the calcaneum or talus. Symptoms of subtalar joint arthritis include pain when walking, loss of motion through the joint's range of motion, and difficulty walking on uneven surfaces. Physical therapy,
orthotics
Orthotics ( el, Ορθός, translit=ortho, lit=to straighten, to align) is a medical specialty that focuses on the design and application of orthoses, or braces. An is "an externally applied device used to influence the structural and functio ...
, and surgery are the main treatment options.
In
flat feet
Flat feet (also called pes planus or fallen arches) is a postural deformity in which the arches of the foot collapse, with the entire sole of the foot coming into complete or near-complete contact with the ground. Sometimes children are born ...
, the joint is typically more horizontal.
References
* Calais-Germain, Blandine. "Anatomy of Movement", Eastland Press, 1993.
Additional images
File:Gray357.png, Coronal section through right talocrural and talocalcaneal joints.
File:Gray359.png, Talocalcaneal and talocalcaneonavicular articulations exposed from above by removing the talus.
External links
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Foot
Joints