The knee on a horse, as with the fetlock joint above it, is one of the most complex areas in the leg. The area contains a number of small bones and ligaments which not only help the knee to maintain stability but also act as shock absorbers. This region is prone to both congenital and acquired lameness problems which compromise a horse’s long term comfort and athletic performance.
The front leg knee is a very important part of the front limb for all horses. It is what allows the horse to swing his front leg forward for propulsion and to come back down onto the ground after he has passed over it. Without this movement the front leg would be more like a strut than a knee and the horse would not be able to move effectively.
While the front leg knee does not flex like a human’s it is actually quite similar to the stifle joint in the back leg. The stifle is formed by the bottom of the femur and the top of the tibia and is held in place by various ligaments. In comparison the front leg knee is made up of 8 bones organized in two rows and three joints. The bones of the knee are called carpi and are somewhat comparable to the bones in a human wrist.
As with all joints in the body the front leg knee is prone to injury. The most common problem is soft tissue damage. These injuries are generally due to trauma and can take weeks or months to heal. It is important to remember that soft tissue damage often has a secondary bone injury as well. This can prolong healing and can result in re-injury.
Conformation is also very important with the front leg knee and conformational defects associated with the knee are associated with increased risk of injury and lameness. The most common conformation defect seen in this region is a ‘turning out’ of the knee which can lead to a chip fracture in the kneecap (carpal).
Other problems include over-training whereby the carpal bones harden and become more likely to crack, or to suffer from external trauma such as being struck by another horse. Cannon bone length is an important factor as a long cannon bone is more likely to develop a chip.
If your horse has been injured it is important to rest the leg as soon as possible. This might mean weeks or even months of confinement and hand-walking followed by a gradual return to exercise as dictated by your veterinarian. Non steroidal anti-inflammatory medication may be given but long term use is discouraged due to the risks of gastrointestinal and kidney complications. The veterinarian will determine if there is an internal problem with the knee structure and advise on a course of treatment.