The ankle, the talocrural region or the jumping bone (informal) is the area where 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 an organ at the terminal part of the leg made up o ...

and the

leg A leg is a weight-bearing and locomotive anatomical structure, usually having a columnar shape. During locomotion, legs function as "extensible struts". The combination of movements at all joints can be modeled as a single, linear element cap ...

meet. The ankle includes three

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- ...

s: the ankle joint proper or talocrural joint, the

subtalar joint In human anatomy, the subtalar joint, also known as the talocalcaneal joint, is a joint 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 pl ...

, and the

inferior tibiofibular joint The inferior tibiofibular joint, also known as the distal tibiofibular joint (tibiofibular syndesmosis), is formed by the rough, convex surface of the medial side of the distal end of the fibula, and a rough concave surface on the lateral sid ...

. The movements produced at this joint are dorsiflexion and plantarflexion of the foot. In common usage, the term ankle refers exclusively to the ankle region. In medical terminology, "ankle" (without qualifiers) can refer broadly to the region or specifically to the talocrural joint. The main bones of the ankle region are the talus (in the foot), the

tibia The tibia (; : tibiae or tibias), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two Leg bones, bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outsi ...

, and

fibula The fibula (: fibulae or fibulas) or calf bone is a leg bone on the lateral side of the tibia, to which it is connected above and below. It is the smaller of the two bones and, in proportion to its length, the most slender of all the long bones. ...

(both in the leg). The talocrural joint is a synovial

hinge joint A hinge joint (ginglymus or ginglymoid) is a bone joint where the articular surfaces are molded to each other in such a manner as to permit motion only in one plane. According to one classification system they are said to be uniaxial (having o ...

that connects the distal ends of the tibia and fibula in the lower limb with the proximal end of the talus. The articulation between the tibia and the talus bears more weight than that between the smaller fibula and the talus.

Structure

Region

The ankle region is found at the junction of the

and the

. It extends downwards ( distally) from the narrowest point of the lower leg and includes the parts of the foot closer to the body (proximal) to the

heel The heel is the prominence at the posterior end of the foot. It is based on the projection of one bone, the calcaneus or heel bone, behind the articulation of the bones of the lower leg. Structure To distribute the compressive forces exerted ...

and upper surface ( dorsum) of the foot.

Ankle joint

The talocrural joint is the only mortise and tenon joint in the human body, the term likening the skeletal structure to the

woodworking joint Joinery is a part of woodworking that involves joining pieces of wood, engineered lumber, or synthetic substitutes (such as laminate), to produce more complex items. Some woodworking joints employ mechanical fasteners, bindings, or adhesives, ...

of the same name. The bony architecture of the ankle consists of three bones: the

, the

, and the talus. The articular surface of the tibia may be referred to as the ''plafond'' ( French for "ceiling"). The

medial malleolus A malleolus is the bony prominence on each side of the human ankle. Each leg is supported by two bones, the tibia on the inner side (medial) of the leg and the fibula on the outer side (lateral) of the leg. The medial malleolus is the promin ...

is a bony process extending distally off the medial tibia. The distal-most aspect of the fibula is called the lateral malleolus. Together, the malleoli, along with their supporting ligaments, stabilize the talus underneath the tibia. Because the motion of the subtalar joint provides a significant contribution to positioning the foot, some authors will describe it as the lower ankle joint, and call the talocrural joint the upper ankle joint. Dorsiflexion and Plantarflexion are the movements that take place in the ankle joint. When the foot is plantar flexed, the ankle joint also allows some movements of side to side gliding, rotation, adduction, and abduction. The bony arch formed by the tibial plafond and the two malleoli is referred to as the ankle " mortise" (or talar mortise). The mortise is a rectangular socket. The ankle is composed of three joints: the talocrural joint (also called talotibial joint, tibiotalar joint, talar mortise, talar joint), the

(also called talocalcaneal), and the

Inferior tibiofibular joint The inferior tibiofibular joint, also known as the distal tibiofibular joint (tibiofibular syndesmosis), is formed by the rough, convex surface of the medial side of the distal end of the fibula, and a rough concave surface on the lateral sid ...

. The joint surface of all bones in the ankle is covered with articular

cartilage Cartilage is a resilient and smooth type of connective tissue. Semi-transparent and non-porous, it is usually covered by a tough and fibrous membrane called perichondrium. In tetrapods, it covers and protects the ends of long bones at the joints ...

. The distances between the bones in the ankle are as follows: *Talus - medial malleolus : 1.70 ± 0.13 mm *Talus - tibial plafond: 2.04 ± 0.29 mm *Talus - lateral malleolus: 2.13 ± 0.20 mm Decreased distances indicate

osteoarthritis Osteoarthritis is a type of degenerative joint disease that results from breakdown of articular cartilage, joint cartilage and underlying bone. A form of arthritis, it is believed to be the fourth leading cause of disability in the world, affect ...

Ligaments

The ankle joint is bound by the strong

deltoid ligament The deltoid ligament (or medial ligament of talocrural joint) is a strong, flat, triangular band, attached, above, to the apex and anterior and posterior borders of the medial malleolus. The deltoid ligament supports the ankle joint and also resi ...

and three lateral ligaments: the

anterior talofibular ligament The anterior talofibular ligament is a ligament in the ankle. It passes from the anterior margin of the fibular malleolus, passing anteromedially to insert at the lateral aspect of the talus at the talar neck , in front of its lateral articular ...

, the

posterior talofibular ligament The posterior talofibular ligament is a ligament that connects the fibula to the talus bone. It runs almost horizontally from the malleolar fossa of the lateral malleolus of the fibula to the lateral tubercle on the posterior surface of the ta ...

, and 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 ligam ...

. * The ''deltoid ligament'' supports the medial side of the joint, and is attached at the

of the tibia and connect in four places to the talar shelf of the

calcaneus In humans and many other primates, the calcaneus (; from the Latin ''calcaneus'' or ''calcaneum'', meaning heel; : calcanei or calcanea) or heel bone is a bone of the Tarsus (skeleton), tarsus of the foot which constitutes the heel. In some other ...

calcaneonavicular ligament The plantar calcaneonavicular ligament (also known as the spring ligament or spring ligament complex) is a complex of three ligaments on the underside of the foot that connect the calcaneus with the navicular bone. Structure The plantar calcan ...

, the

navicular tuberosity The navicular bone is a small bone found in the feet of most mammals. Human anatomy The navicular bone in humans is one of the tarsal bones, found in the foot. Its name derives from the human bone's resemblance to a small boat, caused by th ...

, and to the medial surface of the talus. * The ''anterior'' and ''posterior talofibular ligaments'' support the lateral side of the joint from the lateral malleolus of the fibula to the dorsal and ventral ends of the talus. * The ''calcaneofibular ligament'' is attached at the lateral malleolus and to the lateral surface of the calcaneus. Though it does not span the ankle joint itself, the syndesmotic ligament makes an important contribution to the stability of the ankle. This ligament spans the

syndesmosis A syndesmosis (“fastened with a band”) is a type of fibrous joint in which two bones are united to each other by fibrous connective tissue. The gap between the bones may be narrow, with the bones joined by ligaments, or the gap may be wide a ...

, i.e. the articulation between the medial aspect of the distal fibula and the lateral aspect of the distal tibia. An isolated injury to this ligament is often called a high ankle sprain. The bony architecture of the ankle joint is most stable 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 ...

. Thus, a sprained ankle is more likely to occur when the ankle is plantar-flexed, as ligamentous support is more important in this position. The classic ankle sprain involves the

(ATFL), which is also the most commonly injured ligament during inversion sprains. Another ligament that can be injured in a severe ankle sprain is the

Retinacula, tendons and their synovial sheaths, vessels, and nerves

A number of tendons pass through the ankle region. Bands of connective tissue called ''retinacula'' (singular: ''retinaculum'') allow the tendons to exert force across the angle between the leg and foot without lifting away from the angle, a process called bowstringing. The superior extensor retinaculum of foot extends between the anterior (forward) surfaces of the tibia and fibula near their lower (distal) ends. It contains the anterior tibial artery and

vein Veins () are blood vessels in the circulatory system of humans and most other animals that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are those of the pulmonary and feta ...

and the tendons of the tibialis anterior muscle within its tendon sheath and the unsheathed tendons of extensor hallucis longus and extensor digitorum longus muscles. The deep peroneal nerve passes under the retinaculum while the superficial peroneal nerve is outside of it. The inferior extensor retinaculum of foot is a Y-shaped structure. Its lateral attachment is on the calcaneus, and the band travels towards the anterior tibia where it is attached and blends with the superior extensor retinaculum. Along with that course, the band divides and another segment attaches to the plantar aponeurosis. The tendons which pass through the superior extensor retinaculum are all sheathed along their paths through the inferior extensor retinaculum and the tendon of the fibularis tertius muscle is also contained within the retinaculum. The flexor retinaculum of foot extends from the medial malleolus to the medical process of the calcaneus, and the following structures in order from medial to lateral: the tendon of the tibialis posterior muscle, the tendon of the flexor digitorum longus muscle, the

posterior tibial artery The posterior tibial artery of the lower limb is an artery that carries blood to the posterior compartment of the leg and plantar surface of the foot. It branches from the popliteal artery via the tibial-fibular trunk. Structure The posteri ...

and

, the

tibial nerve The tibial nerve is a branch of the sciatic nerve. The tibial nerve passes through the popliteal fossa to pass below the arch of soleus. Structure Popliteal fossa The tibial nerve is the larger terminal branch of the sciatic nerve with root val ...

, and the tendon of the

flexor hallucis longus muscle The flexor hallucis longus muscle (FHL) attaches to the plantar surface of phalanx of the great toe and is responsible for flexing that toe. The FHL is one of the three deep muscles of the posterior compartment of the leg, the others being the ...

. The fibular retinacula hold the tendons of the fibularis longus and fibularis brevis along the lateral aspect of the ankle region. The superior fibular retinaculum extends from the deep transverse fascia of the leg and lateral malleolus to calcaneus. The inferior fibular retinaculum is a continuous extension from the inferior extensor retinaculum to the calcaneus.

Mechanoreceptors

Mechanoreceptors of the ankle send proprioceptive sensory input to the central nervous system (CNS). Muscle spindles are thought to be the main type of mechanoreceptor responsible for proprioceptive attributes from the ankle. The muscle spindle gives feedback to the CNS system on the current length of the muscle it innervates and to any change in length that occurs. It was hypothesized that muscle spindle feedback from the ankle dorsiflexors played the most substantial role in

proprioception Proprioception ( ) is the sense of self-movement, force, and body position. Proprioception is mediated by proprioceptors, a type of sensory receptor, located within muscles, tendons, and joints. Most animals possess multiple subtypes of propri ...

relative to other muscular receptors that cross at the ankle joint. However, due to the multi-planar range of motion at the ankle joint there is not one group of muscles that is responsible for this. This helps to explain the relationship between the ankle and balance. In 2011, a relationship between proprioception of the ankle and balance performance was seen in the CNS. This was done by using a fMRI machine in order to see the changes in brain activity when the receptors of the ankle are stimulated. This implicates the ankle directly with the ability to balance. Further research is needed in order to see to what extent does the ankle affect balance.

Function

Historically, the role of the ankle in locomotion has been discussed by

Aristotle Aristotle (; 384–322 BC) was an Ancient Greek philosophy, Ancient Greek philosopher and polymath. His writings cover a broad range of subjects spanning the natural sciences, philosophy, linguistics, economics, politics, psychology, a ...

and

Leonardo da Vinci Leonardo di ser Piero da Vinci (15 April 1452 - 2 May 1519) was an Italian polymath of the High Renaissance who was active as a painter, draughtsman, engineer, scientist, theorist, sculptor, and architect. While his fame initially rested o ...

. There is no question that ankle push-off is a significant force in human gait, but how much energy is used in leg swing as opposed to advancing the whole-body

center of mass In physics, the center of mass of a distribution of mass in space (sometimes referred to as the barycenter or balance point) is the unique point at any given time where the weight function, weighted relative position (vector), position of the d ...

is not clear.

Clinical significance

Traumatic injury

Of all major joints, the ankle is the most commonly injured. If the outside surface of the foot is twisted under the leg during weight bearing, the lateral ligament, especially the anterior talofibular portion, is subject to tearing (a

sprain A sprain is a 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 made of collagen that connect two or ...

) as it is weaker than the medial ligament and it resists inward rotation of the talocrural joint.

Fractures

Imaging

The initial evaluation of suspected ankle pathology is usually by

projectional radiography Projectional radiography, also known as conventional radiography, is a form of radiography and medical imaging that produces two-dimensional images by X-ray radiation. The image acquisition is generally performed by radiographers, and the images a ...

("X-ray"). Varus or valgus deformity, if suspected, can be measured with the frontal tibiotalar surface angle (TTS), formed by the mid-longitudinal tibial axis (such as through a line bisecting the tibia at 8 and 13 cm above the tibial plafond) and the talar surface. An angle of less than 84 degrees is regarded as ''talipes varus'', and an angle of more than 94 degrees is regarded as ''talipes valgus''. For ligamentous injury, there are three main landmarks on X-rays: The first is the ''tibiofibular clear space'', the horizontal distance from the lateral border of the posterior tibial malleolus to the medial border of the fibula, with greater than 5 mm being abnormal. The second is ''tibiofibular overlap'', the horizontal distance between the medial border of the fibula and the lateral border of the anterior tibial prominence, with less than 10 mm being abnormal. The final measurement is the ''medial clear space'', the distance between the lateral aspect of the medial malleolus and the medial border of the talus at the level of the talar dome, with a measurement greater than 4 mm being abnormal. Loss of any of these normal anatomic spaces can indirectly reflect ligamentous injury or occult fracture, and can be followed by MRI or CT.

Abnormalities

Clubfoot or talipes equinovarus, which occurs in one to two of every 1,000 live births, involves multiple abnormalities of the foot. Equinus refers to the downard deflection of the ankle, and is named for the walking on the toes in the manner of a horse. This does not occur because it is accompanied by an inward rotation of the foot ( varus deformity), which untreated, results in walking on the sides of the feet. Treatment may involve manipulation and casting or surgery. Ankle joint equinus, normally in adults, relates to restricted ankle joint range of motion(ROM). Calf muscle stretching exercises are normally helpful to increase the ankle joint dorsiflexion and used to manage clinical symptoms resulting from ankle equinus. Occasionally a human ankle has a ball-and-socket ankle joint and fusion of the talo-navicular joint.

History

The word ankle or ancle is common, in various forms, to

Germanic languages The Germanic languages are a branch of the Indo-European languages, Indo-European language family spoken natively by a population of about 515 million people mainly in Europe, North America, Oceania, and Southern Africa. The most widely spoke ...

, probably connected in origin with the

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

, or

Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...

, meaning bent.

Other animals

Evolution

It has been suggested that dexterous control of toes has been lost in favour of a more precise voluntary control of the ankle joint.

Footnotes

References

* * *

Additional images

File:Slide3Bubu.JPG, Dorsum of Foot. Ankle joint. Deep dissection. File:Slide2bubu.JPG, Dorsum of Foot. Ankle joint. Deep dissection. File:Slide2tat.JPG, Ankle joint. Deep dissection. Anterior view. File:Slide2coco.JPG, Dorsum of Foot. Ankle joint. Deep dissection.

External links

* * {{Authority control Foot *Ankle Lower limb anatomy

Structure

Region

Ankle joint

Ligaments

Retinacula, tendons and their synovial sheaths, vessels, and nerves

Mechanoreceptors

Function

Clinical significance

Traumatic injury

Fractures

Imaging

Abnormalities

History

Other animals

Evolution

See also

Footnotes

References

Additional images

External links