Bones of the Foot

BiologyHuman biology

The Foot

The foot is one of the intricate structures comprising 26 bones linked at 33 joints. The foot bones provide mechanical support both while walking and standing by supporting the body weight.

The foot bones are grouped under the following three categories −

  • Tarsals

  • Metatarsals

  • Phalanges.

Tarsals

A set of seven irregular bones form the tarsals situated at the proximal end of the ankle joint. Let us see each set in detail spreading out from the ankle joint.

  • The talus or ankle bone − the two lower leg bones, tibia and fibula, connect with the talus at the top of the ankle joint.

  • The calcaneus or the heel bone − situated just below the talus, the calcaneus or the heel bone is the largest of the tarsal bones and helps in supporting body weight.

  • Cuboid − connecting immediately to the front side of the heel bone is the cuboid on the lateral side of the foot.

The below mnemonic will help remember the tarsals.

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Navicular − It is a curved bone situated between the talus and the cuneiforms

Cuneiforms − A set of three cuneiforms branch out from the navicular to the front. They are called the medial, lateral and intermediate cuneiforms which attach to the metatarsals on the other end.

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Articulations of the Talus

Located superiorly, the talus forms three connections (articulations) to the nearby bones and helps in transmitting the body weight evenly to the foot, description as follows −

  • On the superior side, the talus connects to the bones of the lower leg (tibia and fibula) at the ankle joint.

  • On the inferior side, the talus connects to the calcaneus at the subtalar joint.

  • On the anterior side, the talus connects to the navicular bone at the talonavicular joint.

Proximal Group

The talus is responsible to transfer forces from the tibia to the heel bone. By being wider at the anterior end compared to the posterior end, the talus provides additional stability to the ankle. There are several ligaments attached to the talus while no muscles originate or pass through it.

The calcaneus forms two connections to the bones nearby. On the superior end, the calcaneus connects to the talus at the subtalar joint. On the anterior end, the calcaneus connects to the cuboid at the calcaneocuboid joint.

It is the calcaneus that takes the body weight as the heel hits the ground, protruding posteriorly. Calcaneal tuberosity at the posterior end of the heel bone is where the Achilles tendon connects to the calcaneus.

Intermediate Group

The navicular bone connects to the talus at the posterior end, to the three cuneiform bones at the anterior end and to the cuboid laterally. The navicular attaches to a part of the tibialis posterior tendon at the plantar surface.

Distal Group

The cuboid lies anterior to the calcaneus and attaches to the fourth and fifth metatarsals. This cube-shaped bone is attached to the fibularis longus tendon on the plantar surface. The cuneiforms are wedge-shaped bones giving the foot its arch form. The cuneiforms connect to the metatarsals anteriorly and the navicular posteriorly.

They also attach to several muscles namely anterior tibialis, (a part of) posterior tibialis, fibularis longus, and flexor hallucis brevis.

Metatarsals

Metatarsals are a set of five bones and each has a similar structure. Each elongated metatarsal bone attaches from the tarsal to the phalanges and is numbered 1 to 5, with the toe metatarsal called number 1. From the distal end, each metatarsal bone consists of a head, neck, shaft and base as it extends to the proximal end.

The first three metatarsals attach to the cuneiforms at the proximal end forming the tarsometatarsal joint.

Each metatarsal bone is attached to the adjacent metatarsals forming the intermetatarsal joints laterally.

The head of each metatarsal bone is connected to the respective phalanges distally forming the metatarsophalangeal joint.

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Phalanges

Phalanges are the toe bones. Just like the metatarsals, each phalanx consists of a head, shaft and base. Starting from the metatarsophalangeal joint, second to the fifth toes consist of three phalanges on each toe - proximal, middle and distal phalanges.

The big toe consists of only two phalangeal bones – the proximal and the distal. The metatarsophalangeal joint forms the ball of the fool at the plantar surface.

Ligaments

Several ligaments criss-cross the foot connecting different bones and plays an integral part in supporting the foot and its various functions.

Deltoid ligaments

These ligaments are also known as the medial ligaments that form the bulge on the inside of the ankle. Starting from the end of the tibia, four ligaments spread out to connect the talus, calcaneus and navicular bones. This bone acts as a bridge between the talus on one side and the three shorter bones on the other, which go on to connect the toe bones.

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The following are the four main ligaments of the foot.

  • The plantar fascia ligament

  • The plantar calcaneonavicular ligament (spring ligament)

  • The calcaneocuboid ligament, and

  • The Lisfranc ligaments

The plantar fascia connects the heel bone to the toe bones in the plantar surface of the foot at the metatarsophalangeal joint. Supporting the arch of the foot, this ligament acts as a shock absorbed while walking.

The plantar calcaneonavicular ligament is a thick fibrous band that connects the heel bone and the navicular bone on the plantar surface at the shelf-like facet of the heel. It supports the head of the talus bearing a remarkable amount of body weight.

The calcaneocuboid is a short ligament that connects the calcaneus and the cuboid on the plantar surface. It helps in the movement and strengthening of the foot.

The Lisfranc ligament connects the medial cuneiform and the base of the second metatarsal. This ligament maintains proper alignment between the tarsal and metatarsal bones and also acts as the shock absorber and weight bearer.

Nerves of the Foot

Five main nerves run from the lumbar region and pass through the foot.

Four of the foot nerves are grouped as sciatic nerves. Out of the four sciatic nerves, two nerves – the tibial nerve and the peroneal nerve branch out before they meet the knee joint. The tibial nerve further branches into the sural nerve while the peroneal nerve branches out to form the deep peroneal and superficial peroneal nerve.

The saphenous nerve is the fifth nerve that branches out from the femoral nerve.

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The intricacy in the alignment of the foot bones while making it fit to walk also makes it prone to injuries and fractures. An important structure that helps us in multiple functions such as locomotion and support needs a lot of care.

FAQs

Q1. What are tarsals?

Ans. A set of seven irregular bones form the tarsals situated at the proximal end of the ankle joint. They are the talus, the calcaneus, cuboid, navicular and the cuneiforms (medial, lateral and intermediate).

Q2. What are metatarsals and phalanges?

Ans. Metatarsals are a set of five bones and each has a similar structure. Each elongated metatarsal bone attaches from the tarsal to the phalanges and is numbered 1 to 5, with the toe metatarsal called number 1. From the distal end, each metatarsal bone consists of a head, neck, shaft and base as it extends to the proximal end.

Phalanges are the toe bones. Just like the metatarsals, each phalanx consists of a head, shaft and base.

Q3. What are the main ligaments of the foot?

Ans. The plantar fascia ligament, the plantar calcaneonavicular ligament (spring ligament), the calcaneocuboid ligament, and the Lisfranc ligaments are the four main ligaments of the foot.

Q4. How many nerves run through the foot?

Ans. Five main nerves run from the lumbar region and pass through the foot. Four of them are grouped as sciatic nerves. The saphenous nerve is the fifth nerve that branches out from the femoral nerve.

Q5. How many phalanges are there in each toe?

Ans. Starting from the metatarsophalangeal joint, second to the fifth toes consist of three phalanges on each toe – proximal, middle and distal phalanges. The big toe consists of only two phalangeal bones – the proximal and the distal.

raja
Updated on 13-Oct-2022 11:19:47

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