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Evidence-based physiotherapy and rehabilitation resources
Editorial & review policyHuman Anatomy · Lower limb
The upper limb was built for reach. The lower limb was built to carry you, and every difference between them follows from that. Heavier bones, deeper sockets, stronger ligaments, and a whole architecture devoted to getting weight safely to the ground.
Set the two limbs side by side and the contrast is instructive.
| Upper limb | Lower limb | |
|---|---|---|
| Attaches by | One small joint at the sternum | The sacroiliac joint, massive and almost immobile |
| Girdle | Mobile; the scapula slides freely on the chest | A rigid ring: two hip bones and the sacrum, fused into the pelvis |
| Proximal socket | Shallow glenoid holding a third of the head | Deep acetabulum enclosing most of the head |
| Priority | Range and dexterity | Stability and load transmission |
| Commonest failure | Dislocation | Fracture. The joint usually holds; the bone gives way. |
Figure 1 · How body weight reaches the ground
That chain is worth carrying in your head, because it tells you where to look when something in it fails. A problem anywhere along it changes how load reaches the ground, and the effects show up above and below the site rather than only at it.
Figure 3 · Bones of the lower limb
Illustration to be added
A full articulated plate of the lower limb skeleton, anterior and posterior views side by side. Name every bone: hip bone with ilium, ischium and pubis distinguished by colour, femur, patella, tibia, fibula, tarsals, metatarsals, phalanges. On the hip bone mark iliac crest, anterior and posterior superior iliac spines, ischial tuberosity, ischial spine, acetabulum, pubic tubercle, greater sciatic notch. On the femur mark head, neck, greater and lesser trochanters, intertrochanteric line and crest, linea aspera, medial and lateral condyles and epicondyles, intercondylar fossa. On the tibia mark condyles, tibial tuberosity, anterior border, medial malleolus; on the fibula head, neck and lateral malleolus. Include a small inset showing the neck-shaft angle of the femur and the inward slant of the shaft. Bone warm ivory, navy line work, gold leader lines.
Each hip bone is three bones that fuse during adolescence: ilium above, ischium behind and below, pubis in front. All three meet in the acetabulum, which is why that socket is so strong — it is built from three converging struts.
| Part | Landmarks | Why you need it |
|---|---|---|
| Ilium | Iliac crest, anterior and posterior superior iliac spines, iliac fossa, greater sciatic notch | The crest and both spines are palpable, and they are your reference points for assessing pelvic position. |
| Ischium | Ischial tuberosity, ischial spine, ramus | The tuberosity is what you sit on, and the hamstring origin. The spine is a landmark in the pelvis. |
| Pubis | Body, superior and inferior rami, pubic tubercle, symphyseal surface | The two pubic bones meet at the symphysis, which loosens in pregnancy. |
| Acetabulum | A deep cup with a horseshoe-shaped articular surface and a central notch | Deep enough that dislocation needs major force. |
The longest and strongest bone in the body, and the one whose geometry matters most.
| Region | Features |
|---|---|
| Upper end | Head, with a small pit for the ligament of the head; neck, angled upwards and inwards; greater and lesser trochanters; intertrochanteric line in front and crest behind. |
| Shaft | Smooth and slightly bowed forwards, with the linea aspera, a prominent roughened ridge, running down the back for muscle attachment. |
| Lower end | Medial and lateral condyles with their epicondyles, separated behind by the intercondylar fossa, and the patellar surface in front. |
Two angles that explain a great deal
The neck-shaft angle is roughly 125 degrees in an adult. Increased, the limb is pushed into what is called coxa valga; decreased, coxa vara. Either changes the leverage of the hip abductors and the load on the neck itself.
Because the femoral heads are set wide apart and the knees are not, the shaft slants inwards. That slant is greater in a wider pelvis, which increases the angle at the knee and is one reason patellofemoral problems are more common in women. It is anatomy, not weakness.
The largest sesamoid bone in the body, lying within the quadriceps tendon. It has a roughly triangular shape with the apex pointing down, and its back surface is covered by the thickest articular cartilage anywhere in the body — which tells you how much load passes through it.
Its job is leverage. By holding the quadriceps tendon away from the knee's axis it increases the muscle's moment arm, so the same muscle force produces more turning effect. Remove the patella and quadriceps efficiency falls substantially.
| Tibia | Fibula | |
|---|---|---|
| Role | Carries essentially all the body weight | Carries almost none. It is a strut for muscle attachment and it stabilises the ankle. |
| Upper end | Medial and lateral condyles, intercondylar area, and the tibial tuberosity in front for the patellar tendon | Head, articulating with the tibia below the knee, not part of the knee joint |
| Shaft | Triangular, with a sharp anterior border and a broad medial surface lying directly under the skin | Slender, deeply buried in muscle |
| Lower end | Medial malleolus | Lateral malleolus, which extends further down |
Two consequences of that table
The medial surface of the tibia is subcutaneous along its whole length. That makes it easy to palpate, easy to injure, and slow to heal when the skin over it breaks down.
The lateral malleolus reaches further down than the medial. This blocks eversion more than inversion, which is a large part of why inversion sprains of the ankle are so much commoner.
Twenty-six bones, arranged so the foot can be a rigid lever at one moment and an adaptable platform the next.
Figure 2 · The foot skeleton and its arches
Illustration to be added
Three panels. Panel one: the foot from above with all seven tarsals drawn and colour-separated (talus, calcaneus, navicular, cuboid, and the three cuneiforms), the five metatarsals numbered, and the phalanges. Panel two: the foot from below showing the same bones with the plantar surface, marking the tubercle at the base of the fifth metatarsal and the weight-bearing points at heel and metatarsal heads. Panel three: a medial view in section showing the medial longitudinal arch with its keystone, the lateral longitudinal arch, and the plantar fascia running from calcaneus to the toes, plus the spring ligament supporting the head of the talus. Add a small transverse section across the midfoot showing the transverse arch. Bone in warm ivory, ligaments navy, fascia pale gold.
| Group | Bones | Notes |
|---|---|---|
| Tarsals | Talus, calcaneus, navicular, cuboid, and three cuneiforms | The talus receives the whole body weight from the tibia and has no muscle attached to it at all. The calcaneus is the largest, and takes the heel strike. |
| Metatarsals | Five, numbered from the great toe | The base of the fifth projects backwards as a palpable tubercle, and is a common fracture site. |
| Phalanges | Fourteen: two in the great toe, three in each of the others | Same arrangement as the hand, with far less independent movement. |
The bones are not laid flat. They form arches — a medial longitudinal arch, a lower lateral one, and a transverse arch across the midfoot. The arches are held by bone shape, by ligaments beneath, and by muscles. They are what let the foot absorb load on contact and then stiffen to push off.
Figure 4 · The hip joint and the femoral neck
Illustration to be added
A coronal section through the hip. Show the femoral head deep within the acetabulum, the acetabular labrum deepening the rim, the ligament of the head running to the acetabular fossa, the fibrous capsule attached around the rim and along the intertrochanteric line, and the articular cartilage on both surfaces. Mark the neck-shaft angle clearly with a dotted construction line. In a second panel show the blood supply: the retinacular vessels running along the femoral neck beneath the capsule to reach the head, the artery in the ligament of the head, and a fracture line drawn across the neck cutting the retinacular vessels, to explain avascular necrosis. Bone warm ivory, cartilage pale blue, capsule and ligaments navy, arteries red.
| Landmark | Where |
|---|---|
| Iliac crest and both anterior superior iliac spines | Along the waist and at the front of the pelvis. Your reference for pelvic level. |
| Posterior superior iliac spines | The dimples in the lower back |
| Greater trochanter | The bony prominence at the side of the hip |
| Ischial tuberosity | Deep in the buttock; found with the hip flexed |
| Patella and its borders | At the front of the knee, movable when the quadriceps is relaxed |
| Tibial tuberosity | A bump below the patella; the patellar tendon runs to it |
| Joint line of the knee | Either side of the patellar tendon with the knee bent |
| Head of fibula | Lateral, just below the knee. The common fibular nerve wraps around its neck. |
| Subcutaneous medial tibia | The whole shin |
| Both malleoli | At the ankle; lateral lower than medial |
| Base of the fifth metatarsal | A prominence on the outer border of the foot |
The fibular neck
The common fibular nerve winds round the neck of the fibula, where it is superficial and lies directly on bone. A fracture there, a tight plaster, or prolonged pressure on the outer knee can damage it — producing foot drop. It is the commonest nerve injury in the lower limb and it is easy to cause by careless positioning.
Different job, different design. Here the joints usually hold and the bone breaks.
It carries almost none. It is a muscle attachment and an ankle stabiliser, which is why a length of it can be taken as a graft.
The lateral reaches further down. That asymmetry is why inversion injuries outnumber eversion ones so heavily.
Every muscle passes over it to reach elsewhere. Combined with its cartilage cover, that leaves little surface for vessels, which is why its blood supply is precarious.
A greater inward slant of the femur is anatomy. It changes knee mechanics, and it is a reason to train differently, not a fault to correct.
Sustained pressure there causes foot drop. It is preventable, and preventing it is your job.
Ten questions on this chapter. Tap one to see the answer and the reasoning.
Answer: (C) Every structural difference follows from that: a rigid girdle, a deep socket, heavier bones and stronger ligaments.
Answer: (B) Ilium, ischium and pubis, and all three meet in the acetabulum. That three-way convergence is why the socket is so strong.
Answer: (C) About 125 degrees. An increase is coxa valga and a decrease coxa vara, and either alters abductor leverage and the load on the neck.
Answer: (B) It is a sesamoid whose job is leverage. Removing it reduces the turning effect the same muscle force can produce.
Answer: (C) It transmits almost no weight, does not take part in the knee joint, and serves as a muscle attachment and ankle stabiliser.
Answer: (B) The longer lateral malleolus blocks eversion, so the ankle gives way into inversion far more readily. The strong deltoid ligament medially adds to this.
Answer: (B) Every muscle passes over it to reach elsewhere. With much of its surface covered by cartilage, little area remains for vessels to enter, so its blood supply is precarious.
Answer: (C) The medial surface. It is easily palpated, easily injured, and slow to heal when the overlying skin breaks down.
Answer: (B) The common fibular nerve winds round the fibular neck, superficial and lying on bone. It is the commonest lower limb nerve injury and is easily caused by careless positioning.
Answer: (B) It increases the angle at the knee and alters patellofemoral mechanics. It is normal anatomy, and a reason to train differently rather than a fault.
Everything on this page, in one screen
| Book | What it adds here |
|---|---|
| B D Human Anatomy, Volume 2: Lower Limb, Abdomen and Pelvis Chaurasia |
The standard Indian regional text for this limb. |
| Anatomy and Human Movement Palastanga, Field and Soames |
Bony architecture explained through the loads it carries. |
| Gray's Atlas of Anatomy Drake, Vogl and Mitchell |
Keep the lower limb plates open alongside this chapter. |
| Surface Anatomy Lumley |
For the palpation table, on a living person. |
Reviewed by the Physiotherapist India Team. · Human Anatomy contents