Muscles of the Crus - Horse Anatomy

Introduction

These muscles can be divided into two groups. On the craniolateral aspect of the limb are the flexors of the tarsus and extensors of the digit. On the caudal aspect are the extensors of the tarsus and flexors of the digit.

Craniolateral Muscles of the Crus

These muscles arise from the distal femur or proximal tibia or fibula. Their tendinous insertions are often multiarticular and insert on the metatarsals or phalanges. They are innervated by the peroneal nerve.

Flexors of the tarsus

Cranial Tibial

Origin - the lateral condyle and tuberosity of the tibia.

Insertion - the metatarsal tuberosity and the combined first and second tarsal bones.

Its tendinous insertion has a synovial sheath, and a bursa is present between its medial branch and the medial ligament of the hock.

Peroneus tertius

Origin - extensor fossa of the femur.

Insertion - proximal extremity of the third metatarsal bone and third tarsal bone. Also the calcaneus and fourth tarsal bones.

An almost exclusive tendinous muscle that plays an important part in the stay apparatus.

Extensors of the Digits

Long digital extensor

Origin - extensor fossa of the femur.

Insertion - extensor process of the third phalanx, and the dorsal surfaces of the proximal extremities of the first and second phalanges.

Its tendon of insertion passes over the front of the hock, and is held in place by three annular ligaments and a synovial sheath. The tendon of the lateral digital extensor joins the tendon a hands breath distal of the tarsus.

Lateral digital extensor

Origin - lateral patella ligament, fibula, lateral border of the tibia and the interosseous ligament.

Insertion - the long digital extensor tendon.

It appears to have no function, apart from maybe to support the long digital extensor.

Caudal Muscles of the Crus

These are innervated by the tibial nerve.

Extensors of the Tarsus

Gastrocnemius

Origin - lateral head from the lateral supracondyloid crest of the femur. The medial head from the medial supracondyloid crest.

Insertion - Calcaneus.

The two bellies combine in the middle of the crus, which twists around to the dorsal aspect of the superficial digital flexor. A large bursa lies between these two tendons and a small bursa lies between the gastrocnemius and the its point of insertion on the calcaneus.

Soleus

Origin - the head of the fibula.

Insertion - the gastrocnemius tendon.

Its function is mainly to assist the gastrocnemius.

Flexors of the Digits

Superficial digital flexor

Origin - the supracondyloid fossa of the femur.

Insertion - the calcaneus, the eminences on the sides of the proximal extremity of the second phalanx, and the distal extremity of the first phalanx behind the collateral ligament of the pastern joint.

A large synovial bursa lies under the tendon from the distal fourth of the tibia to the middle of the tarsus. A subcutaneous bursa is sometimes present at the point of the hock.

Deep digital flexor

Origin - the lateral condyle of the tibia, the caudal and medial aspect of the tibia.

Insertion - the semilunar crest and adjacent surface of the cartilage of the third phalanx.

The tendon has a synovial sheath from the distal fourth of the tibia, to a third of the way down the metatarsus.

Muscles of the Crus - Horse Anatomy Learning Resources
Drag and Drop (Dragster) Test your knowledge using drag and drop boxes	Equine Crus and Pes Surface Anatomy Resources (I, II & III)