Tibialis cranial muscle

The tibialis cranial muscle is a muscle of the pelvic limb located craniolaterally to the tibia.

Conformation: It is a flat, long muscle composed of a fleshy body in its proximal portion, which is continued by a distal tendon. This muscle is wide and gradually narrows distally. It fits the lateral fossa of the tibia and the medial surface of the extensor digitorum longus muscle with its flattened shape. The tendon of this muscle is bifid in humans and equines.

Origin: Proximal part of the lateral surface of the tibia, distal to the extensor groove and on the adjacent parts of the tibial tuberosity and lateral tibial condyle.

Insertion: Variable depending on the species, but is either on the metatarsal or on the tarsal bones.

Relations: Covered by the extensor digitorum longus muscle on ungulates. In humans, carnivores and rabbits, it is more superficial and covered directly by the crural fascia. It covers the cranial tibial vessels. Its tendon passes through the retinaculum of crural extensors. It has a passing vagina synovium under the retinaculum. It possesses its own subtendinous bursa in various species.

Action: Flexion of the tarsus and lateral rotation of the paw.

Vascularization: Multiple branches of the cranial tibial vessels.

Innervation: Deep fibular nerve.

Description: The tibialis cranial muscle is located on the craniolateral surface of the tibia. It is flat and long, fitting the lateral fossa of the tibia, and its fleshy part is partialy covered by extensor digitorum longus muscle in ungulates. It is more superficial in humans, carnivores and rabbits, where it partially covers the extensor digitorum longus muscle and is covered by the crural fascia. It covers the tibial cranial vessels, whose branches vascularize the muscle. Its origin is on the proximal part of the lateral surface of the tibia, distal to the extensor groove and on the adjacent part of the tibial tuberosity and lateral tibial condyle. Its tendon passes through the retinaculum of crural extensors, where it is surrounded by the tendinous sheath of cranial tibial muscle to facilitate mouvement. In humans, equines and bovines, it has a small subtendinous bursea. Its insertion depends on the species; it attaches to metatarsal or tarsal bones. The deep fibular nerve innervates this muscle. This muscle causes mainly the flexion of the tarsus. In plurydactyl species, it can cause a slight lateral rotation.

Variations:

• In equines, this muscle is deep, covered by extensor digitorum longus muscle and by the fibularis tertius muscle. It originates from the lateral surface of the tibia, on its most proximal part. Its fleshy part is thin and attaches, on its distal half, to the fibularis tertius muscle. Its tendon passes through the ring formed by the tendon of the fibularis tertius muscle before separating into two endings, one attaching to the fused tarsus I and II and the other to the tuberosity of the third metatarsal. The tarsal ending has its own subtendinous bursea.