Lumps, bumps, bruises and swellings of all types occur frequently in horses. Of these contusions, capped hocks and elbows are the most common, the term "capped" referring to the swollen, distended appearance that these areas take on following trauma.
Trauma to these areas comes in many forms. The hocks are frequently damaged when the horse kicks out and contacts a solid surface. Horses kicking in an enclosed area are more likely to cap a hock. Trailers and small stalls, especially those with walls of concrete or other unforgiving materials, are the most common places for horses to develop problems with capped hocks.
The elbow is a bit different because it is well protected, by the chest wall and the big muscles of the upper leg, from direct contact. The elbow is unique, however, in that it is an area that comes into contact with the horse's foot and shoe when the horse lies down. As the horse curls its leg up under itself, the hoof comes to rest close to the elbow. Horses that have large heel extensions, heel caulks, high pads, or any types of additions to the heels of the shoe will potentially be putting pressure on the elbow area. When the horse lies down, the shoe can sometimes be folded under so quickly that the elbow can be hit with considerable force. Trauma of this nature to the elbow was so common during the height of the draft horse/working horse days that it was given a special name that has survived to this day; repeated trauma to the elbow from an elevated heel shoe results in a swollen irritated area known as a shoe boil.
Many working horses were required to haul heavy loads on cobblestone streets and had large caulks attached to the shoe's heels to provide traction. These caulks would unfortunately irritate the horse's elbows when it lay down. Some horses would wear collars of heavy padded material around the pastern when they were put up at night. These collars served to keep the heel of the shoe away from the elbow.
Capped hocks and shoe boils are the common names for what should more correctly be called hygromas. The point of the hock and the top of the elbow are similar in that they have a synovial bursa - a sac lined by synovial or joint-like tissue - under the skin. This fluid-filled sac reduces the pressure on the tendon as it moves across the bones and helps to keep the tendon from being traumatized by repeated flexing and extending of the hock or elbow joint.
When trauma occurs in these areas, the bursa can be damaged, and the resulting capped appearance is really an increase in the fluid in this sac. If the sac is punctured or opened by the trauma, it can become infected and may be very difficult to heal.
When these hygromas first occur, they are usually hot and tender and the horse may be lame. With time, they cool and there is rarely any lameness associated with an old or chronic hygroma. Treatment in the initial stages should consist of eliminating the cause of the trauma, cold hydrotherapy and rest. Later, when the swelling is cold and non-painful, treatment can be expanded to include topical DMSO applications and injections of steroids into the bursa. Steroids reduce the irritation and lessen the swelling of the sac.
Most problems in the horse are better avoided than treated, and hygromas certainly fit that picture. Yet avoiding them or managing the horse and its environment so that caps and bumps and knots do not occur can be quite difficult As the enlargement gets older it becomes smaller and harder, but is always liable to re-injury.
Padded leg wraps used in transport can help mitigate kicking injuries in the trailer; behavioral modification can reduce stall kicking in some horses. Correct shoeing and pastern roll guards can help prevent elbow injuries. Another method of preventing further aggravation of a capped elbow is to shoe the horse with a special shoe from which the inner quarter and the heel have been removed. It is this part of the shoe which will cause or exacerbate this injury.
But horses will still have parts of the body that stick out and they will still bump, bruise and hit these areas. Capped hocks and shoe boils will still occur. Recognizing these conditions and quickly beginning the appropriate treatment may help lessen their severity and improve the overall appearance of the horse.
Taken From Horse And Horse info