A horse has a well-developed skeleton that provides a rigid framework for support, protection and movement. The skeleton also acts as a storage facility for minerals, principally calcium and phosphorus. The skeleton consists of two main parts; the appendicular skeleton and the vertebral column. The appendicular skeleton includes the bones that form the limbs. This includes the pelvis, which attaches the hindlimb and the scapula, which attaches the forelimb. The vertebral column extends from the base of the skull to the tip of the tail. It consists of approximately 54 individual vertebrae.
The horse has two forelimbs and two hindlimbs, which are adapted for fast running. The forelimbs contain the humerus, radius and ulna. The humerus connects with the scapula to form the shoulder joint. The ulna supports the radius, which forms the elbow joint. The carpal bones, metacarpals, phalanges and sesamoid bones form the hindlimb. The horse’s paw is designed for gripping.
A horse’s ribs are bandlike and vary in length, breadth and curvature. The ribs in the front are curved and thinned at the cranial end, while they become slenderer and thicker as they move caudally to the sternum. The sternum is canoe-shaped and compressed laterally except in its caudal part. The upper ribs are narrower and longer than the lower ones.
In contrast to humans, the scapula of horses is not attached to the humerus and ulna. It is attached to a long rod called the clavicle, which is connected to the humerus via the olecranon process at its proximal end. This connects to the ulna via an interosseous space and carries most of the weight of the arm.
The femur of the horse is a long, strong bone that provides a large surface area for attachment of major muscles that generate power and locomotion. The tibia of the horse is also a long bone. The tibia connects with the fibula to form the knee joint. The patella, which is the equivalent of the human kneecap, provides a shock-absorbing structure for the knee joint.
The tarsus of the horse is made up of six short tarsal bones; the talus, calcaneus and three distal tarsal bones (metatarsal phalanges). There are also three short metatarsal sesamoids. The feet of a horse have four toes. The horse’s hoof capsule has an angle of articulation with the ground of about 30 degrees. The hoof capsule is lined with a tough, strong membrane. This helps to protect the horse’s hooves from wear and tear caused by excessive pressure on the frog or hoof wall. The hoof capsule is also responsible for maintaining the shape of the foot. It is important that a horse’s hoof capsule has a good angle of articulation with the ground, otherwise the foot would be very prone to injury. A good angle of articulation with the ground also helps to reduce bruising and friction. A good hoof capsule can prevent a thrush infection. This condition is a serious threat to the health of the horse and needs to be treated immediately.