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Tibia

Other Terms: Shin bone

Type

long

Description

The tibia is the more massive medial bone of the leg skeleton. It is the second longest bone of the body, only exceeded in length by the femur. Its strong shaft, consisting of thick walls of compact bone, is triangular in cross-section. The shaft expands proximally into a fluted extremity of spongy bone with a flat plateau-like superior surface largely covered with articular cartilage. The smaller distal end is more knob-like with a pronounced medial projection, the malleolus. The shaft has a strong anterior crest with sloping surfaces to either side. The bone is easily palpable throughout its length.

Etymology

Tibia arises from the Latin term meaning a pipe or flute. In later Latin it directly translated as the shin-bone. There is some uncertainty about which name came first, the bone or the flute. It was common in ancient times to fashion flutes or musical pipes from bones. The tibia of birds was often used to create these wind pipes.

Articulations

The tibia articulates with three bones: the femur, the fibula, and the talus. The proximal end of the tibia has two shallow, oval faces on its superior aspect that form the articular cartilage surfaces for the femoral condyles. Posterolaterally on the lateral condyle of the tibia is the inferiorly directed fibular facet. At this surface the fibular head forms a synovial articulation with the tibia. On the distal tibia's lateral aspect the fibular notch receives the distal end of the fibula. This junction is a syndesmotic joint with an intermediate interosseous ligament. The distal end of the tibia forms a surface for articulation with the talus.

Ossification

The tibia ossifies from three centers. The first begins in the middle of the tibial shaft at approximately the seventh week of embryonic life. At birth this center has spread to each end completely defining the tibial body or shaft. Slightly before or just after birth, a second center appears in the center of the proximal end. This begins to slowly ossify. In the tenth year it projects an oblong process antero-inferiorly as the smooth anterior surface of the tibial tuberosity. Sometimes this tuberosity contribution arises as a separate center of ossification which joins the proximal epiphysis. The proximal epiphysis fuses to the shaft anywhere from the sixteenth to twentieth year. The distal epiphyseal center arises from early in the first year to the second year of life. It ossifies with the shaft between the fifteenth and eighteenth year. Both epiphyses ossify with the shaft earlier in females than in males.

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