The front legs support 65% of the horse’s weight at rest and 85% when moving. This puts them under a lot of stress. Faults in front leg conformation have more serious consequences than in the hind legs. They affect speed, athletic ability and soundness in later life.
The forelimbs of the horse, like all four legs, begin high up at the shoulder joint (humeral radial). This is a hinge-like joint that supports the front part of the horse’s body. The next bone down is the long tibia and smaller fibula that make up the lower leg. This is followed by the hock. The hock is another hinge-like joint made up of six small bones, and this is where most strain and wear occurs. Muscles, tendons and ligaments run down the leg from the hock joint.
When a front leg is badly aligned it has to bear extra concussive forces. The leg must be strong enough to cope with the pressure and also have good flexibility. Incorrect alignment can cause lameness, arthritic changes and even arthritis. The front legs are also more vulnerable to injury than the hind legs because they have a greater range of movement.
Ideally, the joints in a horse’s forelimb should be as broad from all sides as possible. This is because a wide joint has more surface area to absorb and dissipate force. The joint between the cannon and pastern is particularly important because it has to be broad from all angles. If it is too narrow (carpal varus) the horse will be out-at-the-knees or pigeon-toed, and this places added strain on the knee bones, the inside portion of the fetlock joints and pasterns. This can lead to a choppy gait, which leads to fatigue in the legs and feet.
It is important to observe a horse’s forelegs when they are at rest, because they can look quite normal. However, when a horse is at the trot or galloping, a poorly-aligned foreleg can become obvious.
The forelegs of a healthy horse are well-aligned at the shoulder, knee and fetlock joints and at the hock. There is a gentle slope in the pastern which helps to give and dissipate force. When the pastern is too steep, it will put strain on the tendons and ligaments in the back of the fetlock joint. This can lead to a painful condition called windpuffs in the back of the fetlock which causes the horse to become sore when it exercises. This is a common problem in young horses. It can be corrected by trimming or shoeing, but the underlying alignment problems may remain.