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The bones of the lower extremity
Last reviewed: 04.07.2025
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The skeleton of the lower limbs consists of their girdle and free parts of the lower limbs.
The lower limb girdle (cingullum membri inferiores) is formed by two pelvic bones, which are practically immobile with the sacrum at the back and with each other at the front. The skeleton of the free part of the lower limb (skeleton membri inferioris liberi) is divided into the proximal section - the femur, the middle section - the tibia and fibula (two bones of the lower leg) and the distal section - the bones of the foot. In the area of the knee joint there is a large sesamoid bone - the patella. The distal section, in turn, is divided into three parts: the bones of the tarsus, the bones of the metatarsus and the phalanges of the fingers.
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Bones of the lower limb girdle
The pelvic bone (os coxae) up to 12-16 years of age consists of three separate bones connected by cartilage: the ilium, pubis and ischium, which at this age fuse with each other.
The ilium (os ilium) consists of two sections. The lower, thickened section - the body of the ilium (corpus ossis ilii) - participates in the formation of the acetabulum. The upper, widened section - the wing of the ilium (ala ossis ilii). It is a wide curved plate, thinned in the center. On the periphery, the wing is thickened, fan-shaped and ends in the iliac crest (crista iliaca).
The pubic bone (os pubis) has an expanded part - the body, and two branches. The body of the pubic bone (corpus ossis pubis) forms the anterior part of the acetabulum. From it, the superior branch of the pubic bone (ramus superior ossis pubis) goes in front with the iliopubic eminence (eminentia iliopubica), located along the line of fusion of the pubic bone with the ilium.
The ischium (os ischii) has a thickened body (corpus ossis ischii), which complements the acetabulum from below and passes anteriorly into the branch of the ischium (ramus ossis ischu).
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Skeleton of the free part of the lower limb
The femur is the longest tubular bone in the human body. It has a body and two ends. At the upper (proximal) end is the head of the femur (caput femoris) for connection with the pelvic bone.
Shin bones
The shin has two bones. The tibia is located medially, and the fibula is located laterally. Each bone has a body and two ends. The ends of the bones are thickened and have surfaces for connection with the femur at the top (tibia) and with the bones of the foot at the bottom. Between the bones is the interosseous space of the shin (spatium interosseum cruris).
The tibia is the thickest bone of the leg. The proximal end of the bone is thickened and forms the medial and lateral condyles (condylus medialis et condylus lateralis). The superior articular surface (facies articularis superior) faces upward and articulates with the condyles of the femur.
The fibula is thin and has the head of the fibula (caput fibulae) at its upper thickened (proximal) end. On the medial side of the head is the articular surface of the head of the fibula (facies articularis cdpitas fibulae) for articulation with the tibia.
The foot (pes) is divided into 3 sections: the tarsus, metatarsus and toes. The skeleton of these sections is the bones of the tarsus (ossa tarsi), the bones of the metatarsus (ossa metatarsalia) and the bones of the toes (ossa digitorum pedis).
Tarsal bones
The tarsus consists of seven spongy bones arranged in two rows. The proximal (back) row consists of two large bones: the talus and the calcaneus. The remaining five bones of the tarsus form the distal (front) row.
Metatarsal bones (ossa metatarsi). They include five tubular short bones. The shortest and thickest is the first metatarsal bone, the longest is the second. Each bone has a body (corpus), head (caput) and base (basis). The bodies of the metatarsal bones have a convexity facing the back. The bases are equipped with articular surfaces for articulation with the bones of the tarsus.
The toes, like the fingers, have a proximal phalanx (phalanx proximalis), a middle phalanx (phalanx media), and a distal phalanx (phalanx distalis).