When caring for a horse, it’s important to understand some basic horse leg anatomy. This information will help you better care for the animals in your sanctuary and prevent common foot problems such as thrush and corns.
A horse’s front legs are much longer than their hind legs. This is because the horse needs to carry more of its own weight on the front legs to aid in locomotion. Fortunately, the structure of the horse’s limbs has evolved to accommodate this increased weight. The front legs articulate with the navicular bone and a short pastern bone (called the coffin bone in humans). There is also a small bone called the navicular sesamoid bone which is tucked behind the pastern and helps stabilize the coffin bone. There are two major tendons that help support the bones and move them: the extensor tendon which attaches to the front of the coffin bone and straightens the leg; and the deep digital flexor tendon which runs down the back of the hoof and wraps around the navicular bone, bending and flexing the leg.
The back of the leg, also known as the frog, is thick and spongy. Its primary purpose is to absorb the initial impact of the horse’s stride. When healthy, the frog has a pliable inner wall that can dissipate shock quickly. The frog also contains sensitive tendons and ligaments. This area should be kept free of debris, as it can harbor germs and lead to thrush.
In addition to providing stability and support, the frog is also responsible for building the sole of the hoof. In healthy horses, the frog is full and has a well-formed ridge that provides traction. The frog is also home to the horse’s sensitive metacarpal (knee) joints, and it can be difficult to diagnose a lameness problem in this area without x-rays.
Lastly, the horse has two bony pencil-like structures in its rear legs: the cannon bone or hock (front) and the splint bone or fetlock (back). The fetlock is a hinge joint that moves the leg forward and backward as it strides. When the fetlock is swollen, it can cause the horse to buck or kick out with its back leg.
The outer hoof wall is pigmented and tough and acts as a shield to protect the internal structures from damage. It is also almost impermeable, so water or other substances that come in contact with it are unable to penetrate the wall. If a horse is suffering from nutritional imbalance or a disease, the outer hoof wall may begin to break down and allow these substances to seep in. This is why it is important to feed a nutritious diet to ensure your horse has a strong, healthy outer hoof wall.