Anatomy of a Horse Leg Bones

anatomy of a horse leg bones

The horse’s leg is composed of a number of bones that form the framework and support structure for tendons and ligaments. These connect muscle to bone (the levers) and position the bones to allow movement. A number of joints in the leg allow movement forward and backward, but the joint in the coffin bone of the hoof allows very little movement.

The lower leg bones are known as the phalanges and include the metacarpals, phalangeal and the coffin bone. The phalangeal bones articulate with each other, allowing the extension/flexion (movement) of the foreleg. The phalangeal joints also provide rotation of the foreleg.

Toward the end of the phalangeal bone are two elongated terminal structures that appear like a claw, the distal phalanx. The distal phalanx is the longest bone in the foot and provides a unique characteristic to the horse’s hoof. The shape of the distal phalanx changes in different horses and is related to hoof conformation.

At the top of the phalangeal is the navicular bone. The navicular bone has an unusually large surface mirroring the angle of the hoof wall and is an ideal site for the attachment of a number of tendons and ligaments. It is also the source of a remarkable number of blood vessels in the hoof.

Just below the navicular bone is the coffin bone. The coffin bone has a similar shape to the navicular but does not have a navicular medulla. It does have a wide surface and an equally impressive amount of blood vessels, but its main function is to provide strength and stability to the hoof.

In addition to their role as the frame of the hoof, the hooves are responsible for absorbing and transmitting forces that occur in a variety of situations. The most common force is the weight of the horse and this is mainly supported by the hind legs. This means that a lot of stresses can be put on the hind feet and the bones within. These bones are constantly rebuilding themselves in response to a variety of factors including hoof trimming, training and nutrition. This can cause them to grow in a natural and desirable manner or in an unnatural and undesirable manner. If these bones are not balanced properly this can result in a serious foot unsoundness known as ringbones. This condition occurs when the long pastern bone is crowded or shortened by the short pastern. This results in uneven distribution of pressure across the hoof and can cause pain and discomfort. Regular hoof trimming and shoeing by a qualified farrier will help prevent this problem. Histological slides of Equus specimens showing a distribution of large nerves and VAN triads are outlined in black, and vascular areas in red. The specimens are from a fetal fetus and an adult horse (Equus caballus). The specimens were prepared from a Ward’s Natural Science pre-fixed in formalin and frozen and then sliced with a band saw. They were then stained with haematoxylin and eosin to create the images.