Swelling of the Hock in Horses

Curb is commonly found condition in highly active horse and is distinguished by swelling in the plantar ligament, the long band of tissue that runs down the lower part of the back of the hind leg, or hock, connecting the bones of the leg and hoof and stabilizing the leg. When this area of the leg becomes inflamed, the horse is said to have “thrown a curb.” The condition is due to a series of traumas to the soft tissue of the distal plantar hock.

Curbing is frequently seen in younger horses, often occurring spontaneously and without obvious reason. This may be because they tend to be highly active and naïve. Likewise, racehorses are commonly afflicted with this painful condition, as are horses that are regularly engaged in physically demanding activities, such as hunting, jumping, or pulling heavy loads (e.g., draft horses, carriage horses).  

The symptoms may seem to come on all of a sudden, and can lead to some lameness if not treated immediately and appropriately. While this injury can be treated successfully in most cases, the pain can reach a  peak of intensity before it gets any better. Conversely, if left untreated, with the horse being forced to continue placing pressure on the injury, curb will reach a chronic stage – the last stage before relief can occur without treatment.

Symptoms and Types

• Inflammation of the plantar ligament (back of the leg close to the foot)
• Curved swelling in the ligament between the hock and the cannon bone
• Swelling below the hock
• Swelling of or above the rear cannon bone
• Warmth in the affected area
• Slight lameness (may seem to come on suddenly)

Causes

Excessive work or an active lifestyle (e.g., hunting, jumping, pulling heavy loads) may all lead to curbing due to the strain on the plantar ligament. Other possible underlying causes include:

• Poor conformation of the hock
• Sickle hock – irregularly angled hock
• Cow hock – legs point outward due to irregularly set back knees

Diagnosis

The veterinarian will examine the horse’s hock joint thoroughly, using ultrasound to gain a better view of the lower leg. Curb can be associated with a number of tissue, ligament or tendon injuries, and in some cases a combination of injures is found to exist.