The fetlock is formed where the cannon bone and the long pastern bone meet. The joint includes two sesamoid bones at the back, which the flexor tendons pass over, and is strengthened by ligaments spanning the cannon and pastern bones.
When a horse is galloping or jumping the joint almost touches the ground when carrying the horse’s full weight. Routine stress combined with poor conformation and or a lack of fitness can result in fetlock injuries.
Before the vet can diagnose a swollen fetlock, it is important to identify the position of the swelling and whether the horse is lame.
Windgalls are soft swellings filled with synovial fluid towards the rear of the fetlock. They are seen in many horses and rarely cause a problem.
Articular windgalls are a swelling of the joint pouch between the suspensory ligament and the cannon bone. Horses commonly have small articular windgalls in all four fetlocks. If there is no pain on flexing the joint and no lameness, there is usually nothing to worry about.
Tendinous windgalls are a swelling of the tendon sheath seen between the suspensory ligament and the flexor tendons. Most horses have tendinous windgalls on the hind fetlocks. Treatment is of little value as they tend to refill with synovial fluid if they are drained.
Wear and tear
Arthritis or degenerative joint disease (DJD) is common in the athletic horse. They can result from an initial injury such as a kick, a chip fracture or wear and tear. The articular cartilage is damaged producing increased friction between the joint surfaces. The joint is painful when flexed, and slightly swollen.
The horse will appear intermittently lame, but the lameness may become more severe after heavy exercise and the vet must be called. Initial treatment is rest, followed by controlled exercise. The vet may inject drugs directly into the joint. However, DJD is incurable.
A septic joint will result in a greater level of lameness. Usually caused by a penetration wound from wire or a kick, it can happen when any foreign material enters the sterile area of the joint capsule.
The pain is so severe that the horse will hardly bear weight on its leg. The fetlock will be swollen, hot and painful, and a small cut is usually visible. If you suspect a septic joint call the vetimmmediately, as the joint will need flushing with saline solution.