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Tibia

Synonyms: cnemis, shinbone
German: Tibia

1 Definition

The tibia is after the femur the second longest bone of the human skeleton. It can be roughly subdivided into the tibial shaft (corpus tibiae) and the two portions involved in knee and ankle functions: (extremitas proximalis and extremitas malleolaris).

2 Anatomy

2.1 Extremitas proximalis

The extremitas proximalis - also called caput tibiae - is a large and bulky bone portion which is formed out of two large bony bulges, the condylus medialis and the condylus lateralis. Anteriorly the structures are coated with two concave cartilage facets.

The media facet has a basic oval shape, the lateral facet is almost round. The central components of both joint surfaces articulate with the two femur condyles; the peripheral sections are in contact with the menisci. Between the articular surfaces one finds the eminentia intercondylaris, to both sides of this a prominent tubercle exists, to which the cartilage surfaces extend. Dorsal and ventral to the eminentia intercondylaris are roughened bone cavities, the fossa intercondylaris anterior tibiae and fossa intercondylaris posterior tibiae. The fibres of the anterior and posterior cruciate ligaments and the medial meniscus radiate into these recesses.

2.2 Corpus tibiae

The tibial shaft (corpus tibiae) has a triangular cross-section and, accordingly, exhibits three surfaces (facies) and 3 edges (margines).

2.2.1 Margo anterior

Also called the "crista anterior", the margo anterior is the forward facing bone margin. It begins at the tibial tuborosity tuberositas tibiae and ends distally at the front edge of the malleolus medialis. In its upper part it projects out in a clear edge form, in the lower part it is smooth and rounded. It serves as an attachment point for the deep layer of the lower leg fascia.

2.2.2 Margo medialis

The medial border is rounded off to a significant degree above and below, but becomes more pronounced in the centre. It begins proximal at the back of the medial condylus and ends distally at the posterior margin of the malleolus medialis. Its upper portions serve as an attachment for the ligamentum collaterale tibiale. Here some fibres of the musculus popliteus also insert. Fibres of the musculus soleus and musculus flexor digitorum longus originate in the middle third.

2.2.3 Margo lateralis

The margo lateralis or crista interossea, is a thin, protruding bone edge, which serves as the attachment point of the membrana interossea cruris. It begins proximally in front of the lateral articular surface and distally it further divides into two lamellae.

2.3 Extremitas distalis

The extremitas malleolaris (also: extremitas distalis) is significantly smaller than the extremitas proximalis. It possesses 5 distinguishable areas. On its medial side it has a distinct protuberance, the malleolus medialis.

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3 Development

During the 7th embryonic week the perichondral ossification of the corpus tibiae begins. In the 10th foetal month or during the 1st life year an endochondral bone core appears at the proximal end, whereas the distal pineal epiphyse acquires its endochondral ossification only at the beginning of the 2nd life year. A closure of the epiphyse occurs distally during the 17th and 19 years of age, proximally between 19 and 20 years of age.

4 Clinic

In X-ray images epiphyseal plates, especially those in the area of ​​the distal epiphyse, can be potentially mistaken for fracture lines.

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