Evidence-based physiotherapy and rehabilitation resources
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Evidence-based physiotherapy and rehabilitation resources
Editorial & review policyHuman Anatomy · Lower limb
Twenty-six bones, thirty-three joints, and the whole weight of the body landing on them thousands of times a day. The foot has to be a soft shock absorber the moment it lands and a rigid lever the moment you push off. This chapter is about how one structure manages to be both.
When your heel strikes the ground the foot must be soft. It has to mould to whatever surface it lands on and absorb the impact. A tenth of a second later, as you push off, the same foot must be a stiff lever or the force from your calf would simply be lost in a collapsing arch.
Almost everything distinctive about the foot exists to switch between those two states. Understand the switch and the rest of the chapter falls into place.
Figure 1 · One foot, two jobs
| Group | Bones | What to remember |
|---|---|---|
| Tarsus (7) | Talus, calcaneus, navicular, cuboid, three cuneiforms | The talus has no muscle attached to it at all. It is moved entirely by the bones around it. |
| Metatarsals (5) | First to fifth | The first is short and thick and carries the most load. The fifth has a prominent base you can feel, and it is a common fracture site. |
| Phalanges (14) | Two in the great toe, three in each of the others | Same pattern as the hand, but built for push-off rather than grip. |
Why the talus matters out of proportion to its size
It is the only bone with no muscular attachment, it transmits the entire body weight from the leg to the foot, and much of its surface is covered in cartilage — which leaves little room for blood vessels to enter. Its blood supply runs largely from distal to proximal, so a fracture across the neck can cut off the body of the bone. That is why talar fractures are watched so carefully for avascular necrosis.
Figure 2 · Bones of the foot
Illustration to be added
Two panels. Panel one: the skeleton of the right foot from above, with all twenty-six bones named - talus, calcaneus, navicular, cuboid and the three cuneiforms, then the five metatarsals and the phalanges - and the tarsal group, metatarsal group and phalangeal group each shaded a different tint so the three regions read at a glance. Mark the base of the fifth metatarsal. Panel two: the same foot from the medial side showing the talus sitting on the calcaneus, with the medial longitudinal arch traced as a line from the calcaneal tuberosity through the talus and navicular to the first metatarsal head, and the three weight-bearing contact points marked with small circles. Bone warm ivory with navy outlines, cartilage pale blue.
The talocrural joint is a hinge. The lower ends of tibia and fibula form a mortise — a three-sided socket — and the upper surface of the talus sits in it.
That talar surface is wider at the front than the back, and this single fact explains a great deal:
| Position | What sits in the mortise | Consequence |
|---|---|---|
| Dorsiflexion, foot pulled up | The wide front of the talus | The joint is packed tight and at its most stable. This is the close-packed position. |
| Plantarflexion, foot pointed | The narrow back of the talus | There is play in the mortise, and the ankle is at its most vulnerable. Almost every sprain happens here. |
The two sides of the ankle are not built the same, and that asymmetry decides which injuries you will actually see.
| Side | Ligament | Character |
|---|---|---|
| Lateral | Anterior talofibular, calcaneofibular, posterior talofibular | Three separate bands. The anterior talofibular is the weakest and is injured first in an inversion sprain. |
| This is by far the commoner side to injure, because the foot rolls inwards more easily than outwards. | ||
| Medial | Deltoid ligament | One thick triangular sheet, far stronger. |
| It is so strong that a severe eversion force often pulls off the tip of the medial malleolus rather than tearing the ligament. | ||
This is the point students most often get wrong. Dorsiflexion and plantarflexion happen at the ankle. Inversion and eversion do not.
| Joint | Movement | Why it matters |
|---|---|---|
| Talocrural (ankle) | Dorsiflexion and plantarflexion | A hinge, and nothing else. |
| Subtalar, talus on calcaneus | Inversion and eversion | This is the joint that lets the foot cope with uneven ground. |
| Midtarsal, talonavicular and calcaneocuboid | Adds to inversion and eversion, and locks or unlocks the forefoot | The switch between soft foot and rigid lever lives here. |
In practice the movements combine. Supination is inversion with adduction and plantarflexion; pronation is the opposite. Those are the terms you will meet in gait analysis.
Figure 3 · The ankle mortise and its ligaments
Illustration to be added
Three panels. Panel one: the ankle from the front with the tibia and fibula forming the mortise and the talus in it, showing the talar surface wider anteriorly than posteriorly - draw the talus in outline above the mortise as well, seen from above, so the wedge shape is unmistakable. Panel two: the lateral side showing the three separate bands of the lateral ligament - anterior talofibular, calcaneofibular, posterior talofibular - drawn as distinct straps. Panel three: the medial side showing the deltoid ligament as one continuous triangular sheet fanning from the medial malleolus. Beneath, a small strip of three foot outlines from behind showing neutral, inversion and eversion, with the subtalar axis marked. Bone ivory, ligaments navy, cartilage pale blue.
The foot is not flat on the ground. It touches at three points — the heel, the head of the first metatarsal, and the head of the fifth — and arches between them.
| Arch | Runs | Held up by |
|---|---|---|
| Medial longitudinal | Calcaneus to the first three metatarsals, through the talus and navicular | The spring ligament beneath the head of the talus, the plantar fascia, and tibialis posterior actively. |
| Lateral longitudinal | Calcaneus to the fourth and fifth metatarsals | Much lower and flatter, and in contact with the ground along most of its length. |
| Transverse | Across the foot at the cuneiforms and metatarsal bases | The tendon of fibularis longus crossing the sole, and the deep transverse ligaments. |
The plantar fascia runs from the calcaneus forwards to the bases of the toes. When you push off and the toes bend upwards, that fascia is pulled taut and wound around the metatarsal heads like a rope around a drum.
Winding it shortens the distance between the front and back of the foot, so the arch rises and the whole foot stiffens — exactly at the moment you need a rigid lever. Then the toes come down, the fascia slackens, and the foot is soft again for the next landing. No muscle has to do anything.
Why this explains heel pain
Every step loads the plantar fascia at its narrow attachment to the calcaneus. Overnight the foot rests in plantarflexion and the tissue settles short. The first steps in the morning stretch it abruptly, which is why the classic complaint is pain that is worst on the first few steps out of bed and then eases — and why calf and fascia length are part of the treatment.
Figure 4 · The arches and the windlass
Illustration to be added
Two panels. Panel one: a medial view of the foot at rest, showing the medial longitudinal arch with the spring ligament under the head of the talus, the plantar fascia running from the calcaneus to the toes, and tibialis posterior passing behind the medial malleolus into the sole. Panel two: the same view with the toes extended at the metatarsophalangeal joints, the plantar fascia drawn taut and wound around the metatarsal heads, and the arch visibly higher - use a faint ghost of the panel one arch behind it so the rise is measurable, and add a curved arrow showing the fascia winding around the drum. Add a small third inset: a cross-section through the metatarsal bases showing the transverse arch with the fibularis longus tendon crossing beneath it. Bone ivory, fascia and ligament navy, muscle brick.
Learn the sole as four layers rather than as a list of muscles. Almost none of them are tested individually, and what matters is the principle: they act together as a set of small stabilisers that fine-tune the arch and grip the ground.
| Layer | Contains |
|---|---|
| First, most superficial | Abductor hallucis, flexor digitorum brevis, abductor digiti minimi |
| Second | The tendon of flexor digitorum longus with the lumbricals, and quadratus plantae |
| Third | Flexor hallucis brevis, adductor hallucis, flexor digiti minimi brevis |
| Fourth, deepest | The interossei, with the tendons of fibularis longus and tibialis posterior |
Nerve supply follows the hand's logic closely. The medial plantar nerve behaves like the median nerve of the foot, and the lateral plantar nerve like the ulnar — supplying the interossei and most of the small muscles.
| Problem | Anatomy behind it | What you find |
|---|---|---|
| Lateral ankle sprain | The narrow back of the talus in the mortise during plantarflexion, and three thin lateral bands | Inversion injury with the foot pointed. Swelling and tenderness in front of and below the lateral malleolus. |
| Talar neck fracture | Blood supply entering distally, and a mostly cartilage-covered bone | Watched for avascular necrosis of the body long after the fracture itself has united. |
| Plantar heel pain | Repeated load at the fascia's narrow calcaneal attachment | Worst on the first steps of the day and after sitting. Often with a tight calf. |
| Calcaneal tendon rupture | Poor blood supply a few centimetres above the insertion | Sudden pain, a palpable gap, and no plantarflexion when the calf is squeezed. |
| Fallen medial arch | Failure of the spring ligament and of tibialis posterior | The arch drops, the heel drifts outwards, and too many toes are visible from behind. |
| Tarsal tunnel syndrome | The tibial nerve passing behind the medial malleolus under a tight retinaculum | Burning in the sole, worse at night, with tingling on tapping behind the malleolus. |
| Hallux valgus | The great toe drifting laterally as the transverse arch spreads | A prominent first metatarsal head, and load shifting onto the lesser metatarsals. |
They happen at the subtalar and midtarsal joints. The ankle is a hinge and does dorsiflexion and plantarflexion only.
The narrow part of the talus is in the mortise there, so the joint is loose by design. Assess it in dorsiflexion too.
The deltoid ligament is a single strong sheet. It more often takes a piece of the medial malleolus with it than tears.
Quiet standing is mostly bone shape, ligament and fascia. Muscles matter when the load rises — walking, running, uneven ground.
The fascia is continuous with the mechanics of the whole foot and a tight calf loads it further. Assess ankle dorsiflexion range.
It is moved by the bones around it. That is why subtalar stiffness changes ankle mechanics so completely.
Ten questions on this chapter. Tap one to see the answer and the reasoning.
Answer: (B) The ankle proper is a hinge doing dorsiflexion and plantarflexion. Inversion and eversion belong to the subtalar and midtarsal joints.
Answer: (B) The talus is wider in front. With the foot pointed, its narrow back sits in the mortise and there is play, which is why most sprains happen in that position.
Answer: (C) It is the weakest of the three lateral bands and the first to fail when the foot rolls inwards in plantarflexion.
Answer: (B) It is far stronger than the three thin lateral bands, so bone gives way before it does.
Answer: (A) No muscle attaches to the talus. It is moved by the bones around it, and its blood supply runs distal to proximal, which is why a neck fracture threatens the body.
Answer: (B) The spring ligament sits directly under the talar head. When it fails along with tibialis posterior, the arch drops.
Answer: (B) Extending the toes winds the plantar fascia around the metatarsal heads, shortening the foot and raising the arch. No muscle contraction is required.
Answer: (B) Overnight the foot rests plantarflexed and the fascia settles short. The first steps stretch it abruptly and then it eases.
Answer: (C) It supplies the interossei and most of the small muscles, just as the ulnar nerve does in the hand. The medial plantar nerve behaves like the median.
Answer: (B) Fibularis longus crosses beneath the sole from the lateral side to the medial, acting like a strap under the transverse arch.
Everything on this page, in one screen
| Book | What it adds here |
|---|---|
| Anatomy and Human Movement Palastanga, Field and Soames |
The clearest account of the arches, the windlass and the locking of the midtarsal joint. |
| B D Human Anatomy, Volume 2 Chaurasia |
The layers of the sole and the regional detail at examination level. |
| Clinical Anatomy by Regions Snell |
The clinical consequences of injury around the ankle. |
| Gray's Atlas of Anatomy Drake, Vogl and Mitchell |
Keep the foot plates open while reading the sole. |
Reviewed by the Physiotherapist India Team. · Human Anatomy contents