human anatomy The human body is the structure of a human being. It is composed of many different types of cells that together create tissues and subsequently organ systems. They ensure homeostasis and the viability of the human body. It comprises a head ...

, 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 The foot ( : feet) is an anatomical structure found in many vertebrates. It is the terminal portion of a limb which bears weight and allows locomotion. In many animals with feet, the foot is a separate organ at the terminal part of the leg mad ...

. It occurs at the meeting point of the talus and the

calcaneus In humans and many other primates, the calcaneus (; from the Latin ''calcaneus'' or ''calcaneum'', meaning heel) or heel bone is a bone of the tarsus of the foot which constitutes the heel. In some other animals, it is the point of the hock. ...

. The joint is classed structurally as a

synovial joint A synovial joint, also known as diarthrosis, joins bones or cartilage with a fibrous joint capsule that is continuous with the periosteum of the joined bones, constitutes the outer boundary of a synovial cavity, and surrounds the bones' articulat ...

, and functionally as a

plane joint A plane joint (arthrodial joint, gliding joint, plane articulation) is a synovial joint A synovial joint, also known as diarthrosis, joins bones or cartilage with a fibrous joint capsule that is continuous with the periosteum of the joined bones ...

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 In geometry, a subset ...

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 In humans and many other primates, the calcaneus (; from the Latin ''calcaneus'' or ''calcaneum'', meaning heel) or heel bone is a bone of the tarsus of the foot which constitutes the heel. In some other animals, it is the point of the hock. S ...

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 The posterior talocalcaneal ligament (posterior calcaneo-astragaloid ligament) connects the lateral tubercle of the talus with the upper and medial part of the calcaneus In humans and many other primates, the calcaneus (; from the Latin ''calcan ...

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 The medial talocalcaneal ligament (internal calcaneo-astragaloid ligament) connects the medial tubercle of the back of the talus with the back of the sustentaculum tali. Its fibers blend with those of the plantar calcaneonavicular ligament The ...

extends from the medial tubercle of the talus to the

on the medial surface of the calcaneus. A

synovial membrane The synovial membrane (also known as the synovial stratum, synovium or stratum synoviale) is a specialized connective tissue that lines the inner surface of capsules of synovial joints and tendon sheath A tendon sheath is a layer of synovial m ...

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 Inversion or inversions may refer to: Arts * , a French gay magazine (1924/1925) * ''Inversion'' (artwork), a 2005 temporary sculpture in Houston, Texas * Inversion (music), a term with various meanings in music theory and musical set theory * ...

and

eversion Eversion (from the verb "evert") is the process of turning inside-out. Eversion may refer to: * Eversion (kinesiology), the anatomical term of motion denoting the movement of the sole of the foot away from the median plane * ''Eversion'' (video g ...

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 ...

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 relative ...

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 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 ...

and

supination 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 midfoot to occur.

Pathology

The subtalar joint is particularly susceptible to

arthritis Arthritis is a term often used to mean any disorder that affects joints. Symptoms generally include joint pain and stiffness. Other symptoms may include redness, warmth, swelling, and decreased range of motion of the affected joints. In some ...

, especially when it has previously been affected by

sprain A sprain, also known as a torn ligament, is an acute soft tissue injury of the ligaments within a joint, often caused by a sudden movement abruptly forcing the joint to exceed its functional range of motion. Ligaments are tough, inelastic fibers ...

s 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 functi ...

, 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

* {{Authority control Foot Joints