Tibia

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The tibia (plural: tibiae) is the largest bone of the leg and contributes to the knee and ankle joints. (shin- or shank-bone are lay terms). It is medial to and much stronger than the fibula, exceeded in length only by the femur.

Gross anatomy

Osteology

The tibia has a prismoid shaft, expanded ends, proximal larger condylar shelf articulating at the knee, and distal smaller end with a strong medial malleolus forming the ankle.

Proximal tibia

The tibia has a broad weight-bearing surface consisting of the medial and lateral condyles, each having an articular concave surface and internal intercondylar tubercles projecting superiorly into the knee. The intercondylar area separates the medial and lateral plateau and is divided into the anterior and posterior areas. The anterior intercondylar area houses the attachment of the anterior cruciate ligament, anterior horn of medial meniscus and a small part of the anterior horn of lateral meniscus. The posterior intercondylar area inclines down and back, exhibits a medial intercondylar tubercle for the posterior cornu of the medial meniscus and a smooth tapering ridge for attachment of the posterior cruciate ligament.

The tibial tuberosity is a bony projection of the area where the anterior condylar surface merges. It receives the patellar tendon attachment and is separated from the skin by the subcutaneous infrapatellar bursa.

Gerdy's tubercle is located at the anterolateral aspect of the proximal tibia, where the iliotibial band (ITB) attaches.

Shaft

The diaphysis of the tibia is triangular in cross section and has medial, lateral and posterior surfaces, separated by the anterior, lateral (interosseous) and medial borders. The shaft is thinnest at the junction of middle and distal thirds.

Distal tibia

The slightly expanded end of the tibia is rotated laterally (tibial torsion) and has five surfaces, namely, anterior, posterior, medial, lateral and distal. The lateral surface exhibits a triangular notch which attaches to the fibula.

Articulations

The medial and lateral condyles articulate with corresponding femoral condyles at the knee. The lateral condyle of the proximal tibia has a circular facet articulating with the fibula at the proximal tibiofibular joint.

The distal articular surface of tibia is concave sagittally and slightly convex transversely. The concave surface (also called the sellar surface) fits over the dome of talus at the talocrural joint (a.k.a. tibiotalar joint)

Attachments
Musculotendinous
Ligamentous
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Relations

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Blood supply

  • genicular arterial anastomosis supplies the proximal metaphysis
  • posterior tibial artery branch, the nutrient artery which enters through the nutrient foramen at the level of soleal line, is the major arterial supply
  • anterior tibial artery branch, the periosteal arteries
  • arterial anastomosis at ankle supplies the distal end of tibia

Nerve supply

Proximally innervated by branches supplying the knee joint, distally by those supplying the ankle. The periosteum of the diaphysis receives nerve twigs from the overlying muscles attaching to the tibia.

Variant anatomy

Radiographic features

Plain radiograph
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Development

Ossification

The tibia ossifies from three centers, one in the diaphysis and one each at proximal and distal epiphysis.

The diaphyseal ossification center appears at seventh week antenatally. The proximal ossification center appears at birth and fuses at sixteenth year in females and eighteenth year in males. The distal ossification center appears at the first year of life and joins the shaft at fifteenth year in females and seventeenth year in males.

The medial malleolus is merely an extension from the distal epiphysis and ossifies at seventh year of life.

Related pathology

Anatomy: Lower limb

Anatomy: Lower limb