Comparative anatomy of the tibia

Tibia
The tibia is one of the major weight bearing bones of the hind limb and is involved in both the stifle and hock. The tibia can be divided into three distinct sections:

1.Proximal Extremity

It is three sided and has two condyles which are separated by the popliteal notch on its caudal aspect. The condyles have an articular surface which articulates with its corresponding femoral condyle or the distal surface of the meniscus. In between these articular surfaces lies the intercondylar eminence. The central intercondylar area divides this into a higher medial part and a lower lateral part. Cranial and caudal to the eminence are depressions where ligaments attach. The lateral side of the condyle has an articular facet for the articulation with the fibula. The extensor groove is a large notch on the craniolateral aspect which allows passage of the long digital extensor muscle.

2.Tibial Shaft

It is craniocaudally compressed. The tibial tuberosity/tibial crest projects cranially from the proximal part of the shaft and is an important palpable landmark. The cranial border of the tibia is an extension of the crest distally. It divides the cranial aspect of the shaft in two. The medial aspect is subcutaneous and the lateral aspect is covered in muscles.

3. Distal Extremity

This carries the cochlea which has two grooves divided by a ridge. This central ridge is directed sagittally in most species. The cochlea articulates with the trochlear ridges of the talus. The medial malleolus lies on the medial side of the cochlea and is a bony protuberence. The lateral aspect of the cochlea is highly variable in domestic species.

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Fibula
The fibula lies laterally to the tibia and proximally doesn't interact with the stifle joint. The fibula consists of a proximal head, a neck, a shaft and a distal extremity/lateral malleoulus. During evolution, the fibula has been reduced in size and so also in relative strength and function. The amount of reduction is highly variable in domestic species.

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