There are over 200 bones in a horse’s body, and they work together to make up the skeleton. These bones create a rigid frame for support, protection and movement. Proper nutrition during the horse’s early formative years will encourage healthy bone growth. When the bones are aligned correctly, they work efficiently to allow movement without unnecessary strain on tendons and ligaments.
The skeletal structure of the horse is divided into two parts, the axial skeleton and the appendicular skeleton. The axial skeleton is essentially the ribcage and the backbone, which provides a stable frame for movement. The appendicular skeleton is comprised of the bones that make up the forelimbs and hindlimbs.
Compared to other quadrupeds, the equine skeleton has a greater proportion of long bones. This is due to the horse’s longer legs and larger feet, which need more stability. The articulation between the long bones is also wider and more flexible than in other quadrupeds, and this allows for a greater range of movement.
A horse’s ribcage is made up of six pairs of sternal and costal bones. These bones are attached to the sternal plate, which is in turn connected to the thoracic spines. The thoracic spines are broad dorsoventrally and wide, especially caudally, with a pair of tubercles replacing the ventral crest. In the last four or five thoracic vertebrae there is no transverse foramen, and in some horses, this number can drop to eighteen.
The tibia bone of the lower leg is long and quadrangular with a ridge groove running along its anterior surface (known as the tuberosity). At the proximal extremity of the tibia, there are lateral and medial saddle-shaped articular surfaces for the femur. There is a distal articular surface for the calcaneus with a ridge groove and a distinct eminence called the intercondyloid ridge.
This bone is one of the strongest in the skeleton. It articulates with the scapula to form the shoulder joint and with the radius and ulna to form the elbow joint. It is angled inward at the proximal end to allow for maximum shock absorption during movement.
The carpus, which forms the foot of the front limb, is composed of a short pastern and a long pedal bone, with a third bone known as the accessory or cannon bone. The metacarpals are numbered from II to IV, with the third or large metacarpal bearing weight. The foot is further characterized by the presence of three sesamoids, two proximal ones located at the back of the short pastern and incorporated in the coffin joint and one distal one that is encapsulated within the hoof. These act as pulleys to help reduce friction at the flexor tendon as it moves through the joint.