Within the armpit and groin run very large vessels and nerves. Wounds to either these areas are fairly common in horses, and range greatly in severity. Wounds here are often large and deep, and usually happen when a horse rears or jumps and comes down on an upright rigid post.

Another cause of this injury is a gore wound from a bull (I actually treated a horse that had been gored in the armpit by a bull elk). In some cases, there is foreign material such as wood splinters still deeply embedded in the wound. This can cause the wound to continue to drain and not heal.

The most important factor is the location and depth of the wound and the structures involved. These injuries can be life-threatening if they involve an important internal organ or structure. However, this area has an amazing ability to heal with time and basic nursing care.