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.

Down the drain

Occasionally, injuries to the bursa are drained. This makes an
immediate improvement in the capped appearance, but it may not be
a long-term solution.

Bursal sacs tend to secrete more fluid, and the area simply fills
up again. Sometimes the swelling ends up looking larger than
before the sac was drained.

Tight wraps are sometimes placed over the recently drained sac in
an effort to keep the area from refilling. Both the point of the
hock and the elbow are difficult areas to wrap, however, and the
cosmetic results are not always satisfactory. Additionally, the
drained sac can become infected, leading to more significant
problems. For these reasons, surgical drainage or opening of
these hygromas is rarely recommended.