In many animals with feet, the foot is a separate[clarification needed] organ at the terminal part of the leg made up of one or more segments or bones, generally including claws and/or nails.

[1] The human foot is a strong and complex mechanical structure containing 26 bones, 33 joints (20 of which are actively articulated), and more than a hundred muscles, tendons, and ligaments.

The two long bones of the lower leg, the tibia and fibula, are connected to the top of the talus to form the ankle.

Connected to the talus at the subtalar joint, the calcaneus, the largest bone of the foot, is cushioned underneath by a layer of fat.

The slight mobility of these arches when weight is applied to and removed from the foot makes walking and running more economical in terms of energy.

With the cuboid serving as its keystone, it redistributes part of the weight to the calcaneus and the distal end of the fifth metatarsal.

The tibia and fibula and the interosseous membrane separate these muscles into anterior and posterior groups, in their turn subdivided into subgroups and layers.

[6] Extensor group: the tibialis anterior originates on the proximal half of the tibia and the interosseous membrane and is inserted near the tarsometatarsal joint of the first digit.

In the non-weight-bearing leg, the tibialis anterior dorsiflexes the foot and lift its medial edge (supination).

The extensor digitorum longus arises on the lateral tibial condyle and along the fibula, and is inserted on the second to fifth digits and proximally on the fifth metatarsal.

[8] The superficial layer of posterior leg muscles is formed by the triceps surae and the plantaris.

The flexor hallucis longus arises on the back of the fibula on the lateral side, and its relatively thick muscle belly extends distally down to the flexor retinaculum where it passes over to the medial side to stretch across the sole to the distal phalanx of the first digit.

The flexor hallucis brevis arises on the medial cuneiform bone and related ligaments and tendons.

The adductor hallucis is part of this group, though it originally formed a separate system (see contrahens).

[14] Due to their position and function, feet are exposed to a variety of potential infections and injuries, including athlete's foot, bunions, ingrown toenails, Morton's neuroma, plantar fasciitis, plantar warts, and stress fractures.

This leaves humans more vulnerable to medical problems that are caused by poor leg and foot alignments.

Also, the wearing of shoes, sneakers and boots can impede proper alignment and movement within the ankle and foot.

For example, high-heeled shoes are known to throw off the natural weight balance (this can also affect the lower back).

A pedorthist specializes in the use and modification of footwear to treat problems related to the lower limbs.

During the gait cycle the foot can pronate in many different ways based on rearfoot and forefoot function.

An individual who neutrally pronates initially strikes the ground on the lateral side of the heel.

This rolling inward motion as the foot progresses from heel to toe is the way that the body naturally absorbs shock.

As with a neutral pronator, an individual who overpronates initially strikes the ground on the lateral side of the heel.

Similarly, an overpronator's arches will collapse, or the ankles will roll inward (or a combination of the two) as they cycle through the gait.

As the individual transfers weight from the heel to the metatarsus, the foot will not roll far enough in a medial direction.

Some people consider it rude to wear shoes into a house and sacred places in multiple cultures like Māori Marae, which should only be entered with bare feet.

The number of metatarsals are directly related to the mode of locomotion with many larger animals having their digits reduced to two (elk, cow, sheep) or one (horse).

The metatarsal bones of feet and paws are tightly grouped compared to, most notably, the human hand where the thumb metacarpal diverges from the rest of the metacarpus.