Tarsus (skeleton)
Cluster of seven bones forming the ankle and hindfoot.
The tarsus is a group of seven bones in each foot that connect the lower leg bones (tibia and fibula) to the metatarsus. These seven bones are divided into the hindfoot—made up of the talus and calcaneus—and the midfoot, which includes the cuboid, navicular, and three cuneiform bones (medial, intermediate, and lateral). The tarsus meets the metatarsus, which then connects to the toe bones (proximal phalanges). The joint where the tibia and fibula meet the tarsus is called the ankle joint. The largest tarsal bone is the calcaneus, which bears weight in the heel.
The talus, or ankle bone, connects above with the tibia and fibula to form the talocrural (ankle) joint, and below with the calcaneus at the subtalar joint. Together, the talus and calcaneus make up the hindfoot. The five irregular midfoot bones—cuboid, navicular, and three cuneiforms—form the foot’s arches, which absorb shock. Muscles and the plantar fascia link the midfoot to the hindfoot and forefoot.
Subtalar joint motion is complex, occurring in three planes and producing inversion and eversion. This joint, along with the transverse tarsal joint (which includes the talonavicular and calcaneocuboid joints), converts tibial rotation into forefoot supination and pronation. The subtalar joint’s axis of rotation angles upward 42 degrees from horizontal and 16 degrees medially from the foot’s midline. The subtalar facets form a screw-like shape (right-handed in the right foot), so during inversion, the calcaneus rotates clockwise and shifts forward along the screw axis. Typical subtalar motion ranges from 20 to 30 degrees of inversion and 5 to 10 degrees of eversion; during walking, functional motion is about 10 to 15 degrees, with the heel striking the ground in slight inversion then quickly everting.
The transverse tarsal joint (Chopart’s joint) has two axes. Inversion and eversion occur around a longitudinal axis angled 15 degrees upward and 9 degrees medially. Flexion and extension happen around an oblique axis angled 52 degrees upward and 57 degrees forward-inward. In laboratory tests, the talonavicular joint moves about 7 degrees in flexion-extension and 17 degrees in pronation-supination, while the calcaneocuboid joint moves about 2 degrees in flexion-extension and 7 degrees in pronation-supination.
The subtalar and transverse tarsal joints work together to make the foot flexible or rigid. When the subtalar joint is everted, the two transverse joint axes are parallel, allowing movement. When the subtalar joint is inverted, those axes converge, locking the transverse joint and making the midfoot rigid.
In primitive tetrapods like *Trematops*, the tarsus had three rows of bones: three proximal tarsals (tibiale, intermedium, fibulare), a row of four centralia, and five distal tarsals (each connecting to a metatarsal). Most living tetrapods have modified this pattern through bone loss or fusion. Reptiles and mammals typically have only two proximal tarsals: the calcaneus (from the amphibian fibulare) and the talus (likely a fusion of several bones). In mammals, including humans, the talus forms a hinge joint with the tibia—especially developed in artiodactyls—and the calcaneus forms a heel for the Achilles tendon; reptiles lack these adaptations. The fifth distal tarsal disappeared early in evolution, and the remaining ones became the cuneiform and cuboid bones. Reptiles usually keep two centralia, while mammals typically have just one (the navicular). In birds, the tarsus is gone: the proximal tarsals fused with the tibia, the centralia vanished, and the distal tarsals fused with the metatarsals into a single tarsometatarsus, giving the leg a third segment.
- field
- Human anatomy
- known_for
- Cluster of seven articulating bones in each foot forming the ankle and hindfoot
Quick Facts
- Latin
- ossa tarsi
- Partof
- Foot
Facts from the source article.
Lore & Background
In humans, the largest bone in the tarsus is the calcaneus, which is the weight-bearing bone within the heel of the foot. The talus bone, or ankle bone, is connected superiorly to the tibia and fibula to form the ankle joint (talocrural joint) and inferiorly, at the subtalar joint, to the calcaneus. Together, the talus and calcaneus form the hindfoot. The five irregular bones of the midfoot—the cuboid, navicular, and three cuneiform bones—form the arches of the foot, which serve as a shock absorber. The midfoot is connected to the hind- and forefoot by muscles and the plantar fascia. The complex motion of the subtalar joint occurs in three planes and produces subtalar inversion and eversion. Along with the transverse tarsal joint (talonavicular and calcaneocuboid joint), the subtalar joint transforms tibial rotation into forefoot supination and pronation. The axis of rotation in the joint is directed upward 42 degrees from the horizontal plane and 16 degrees medially from the midline of the foot. The subtalar facets form a screw or Archimedean spiral (right-handed in the right foot) about which subtalar motion occurs. Average subtalar motion is 20-30 degrees inversion and 5-10 degrees eversion. In primitive tetrapods, such as Trematops, the tarsus consists of three rows of bones: three proximal tarsals, a second row of four centralia, and a row of five distal tarsals. In reptiles and mammals, there are normally just two proximal tarsals: the calcaneus (equivalent to the amphibian fibulare) and the talus (probably derived from a fusion of multiple bones). In mammals, including humans, the talus forms a hinge joint with the tibia, and the calcaneus is modified to form a heel for the attachment of the Achilles tendon. In birds, the tarsus has disappeared, with proximal tarsals fusing with the tibia and distal bones fusing with the metatarsals to form a single tarsometatarsus bone.
Reader's Guide
The tarsus is significant as the structural foundation of the foot and ankle, enabling weight-bearing, locomotion, and shock absorption. Its seven bones—the talus, calcaneus, cuboid, navicular, and three cuneiforms—form the hindfoot and midfoot, articulating with the lower leg bones above and the metatarsals below. The largest tarsal bone, the calcaneus, bears the body's weight through the heel. The subtalar joint's complex three-plane motion, with an axis oriented 42 degrees upward and 16 degrees medially, allows inversion and eversion essential for adapting to uneven terrain. The transverse tarsal joint (Chopart's joint) has two axes of motion, contributing to foot flexibility or rigidity depending on subtalar position. In comparative anatomy, the tarsus shows evolutionary variation: primitive tetrapods had three rows of bones, while reptiles and mammals typically have two proximal tarsals (calcaneus and talus). Mammals uniquely developed a hinge joint between the talus and tibia and a calcaneal heel for the Achilles tendon. Birds have fused tarsal bones into a tarsometatarsus. These adaptations highlight the tarsus's role in diverse locomotor strategies across vertebrates.
Did You Know?
- The largest bone in the human tarsus is the calcaneus, which is the weight-bearing bone within the heel.
- The subtalar joint's axis of rotation is directed upward 42 degrees from the horizontal plane and 16 degrees medially from the midline of the foot.
- In primitive tetrapods such as Trematops, the tarsus consisted of three rows of bones: proximal tarsals, centralia, and distal tarsals.
- In birds, the tarsus has disappeared, with proximal tarsals fusing with the tibia and distal bones fusing with the metatarsals to form a single tarsometatarsus bone.
Frequently Asked Questions
What is the Tarsus (skeleton)?
The tarsus is a group of seven small bones in each foot that together form the structural base of the ankle and the back portion of the foot. It acts as the bridge between the lower leg (tibia and fibula) and the midfoot and forefoot.
How many bones make up the Tarsus (skeleton)?
Each foot contains exactly seven tarsal bones, split into two subgroups. The hindfoot contributes the talus and calcaneus, while the midfoot contributes the navicular, medial, intermediate, and lateral cuneiforms, plus the cuboid.
Where exactly is the Tarsus (skeleton) positioned in the body?
It sits directly below the distal ends of the tibia and fibula and directly above the metatarsal bones of the forefoot. The joint formed where the lower leg meets the tarsus is what is commonly referred to as the ankle joint proper.
What are the individual bones within the Tarsus (skeleton)?
The seven members are the talus, calcaneus, navicular, medial cuneiform, intermediate cuneiform, lateral cuneiform, and cuboid. Together they create the arches and articulating surfaces that support weight-bearing and foot movement.
How does the Tarsus (skeleton) connect to the rest of the foot and leg?
It articulates superiorly with the tibia and fibula to form the ankle joint, and inferiorly with the metatarsus, which in turn links to the proximal phalanges of the toes. This continuous chain of joints allows the foot to flex, extend, and carry the body's weight.
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