The limbs are the primary means of locomotion in horses and, therefore, must be strong and healthy. However, the skeletal structure of the horse is very different from that of humans and many horses with incorrect conformation can suffer serious problems in their legs. These problems may be minor and cause discomfort, but they can also lead to lameness or abnormal gait. It is important to understand the muscles and bones in the horse’s limbs to be able to diagnose and treat problems.
The horse has a pelvis that provides the base for the limbs, and a series of short, strong bones that act as the limbs’ attachment points. The major muscles of the hind limb are attached to the femur, which is very large and powerful. The tibia, a long bone that runs down the leg, is connected to the pelvis by an articulation with the fibula. The articulation of the femur and tibia forms the stifle joint, which is supported by a strong, flexible kneecap called the patella.
In the stifle, the femur is articulated with a long bone in the tibia known as the tibial tuberosity. The tibia has two other bony projections, the medial malleolus and the lateral malleolus, that allow the joint to be stabilized by the cruciate ligaments. The stifle is also supported by three patellar ligaments.
The distal femur has medial and lateral condyles that articulate with the tibial plateaux. The tibial plateaux is supported by the calcanean tuber(osity). The ulna and radius are fused into a single bone, which is used to bear weight. The olecranon process on the proximal end of the ulna forms the point of the elbow (fig. 4).
There is a small, bony opening in the pelvis called the lesser sciatic foramen, which exits through the sacrosciatic ligament in BOVINE and BUFFALO and through the internal obturator foramen in EQUINE. The caudal gluteal muscle (DDF_P) extends over this joint.
The bones in the horse’s feet are referred to as the phalanges and are located in the forefoot and hind foot. The phalanges are composed of a proximal phalanx, middle phalanges, and distal phalanges. The proximal phalanx has a sesamoid bone. The middle phalanges have a triangular-wedge shape and are shaped to resemble human metatarsal joints. The proximal phalanges connect to the navicular bone in the inner forefoot and to the talus in the outer forefoot. The distal phalanges connect to the hoof cartilages. The navicular bone, which is also called the coffin bone, is a long ovoid-shaped bone (1 in each equine foot and 2 in each bovine foot). It is located in the heel of the RIGHT forefoot. The navicular bone has a dorsal surface with a groove, and the lateral and medial cuneiform bones are situated on its dorsal side. The lateral cuneiform bone has a deep groove in which the phalanges fit. The navicula are ovoid, splint-shaped, and have dorsal and ventral surfaces. The navicula are surrounded by the cuspidal plate and are firmly connected to the phalanges.