It can be certainly be frightening if you come out one day and see one of your horse’s legs swollen to two to three times the normal size, and clearly having pain and lameness. Possibilities include a leg fracture or another musculoskeletal injury, so call your vet to examine the horse. However, another possibility is a skin infection called cellulitis and in some cases, it is unknown how the infection develops. Dr. Margaret Mudge with Ohio State indicates in Equus magazine that the bacteria may already be in the tissue or could be introduced through the skin by punctures that are unable to be found. Or the condition can occur when bacteria are introduced through a wound or surgical incision. Multiple types of bacteria can be involved, so usually your vet will take a sample to attempt to identify the bacterial organism causing the problem.
Commonly these infections affect the back legs and if not treated aggressively, the infection can enter deeper structures like joint and tendon sheaths, and can be deadly. Also, if the horse cannot stand on the affected leg, laminitis or founder can occur in the other rear leg as it is supporting all of the horse’s weight. Treatment includes intravenous antibiotics, anti-inflammatories and cold hosing to help remove the swelling. Once the horse has less pain, exercise is the most helpful treatment to reduce swelling but wrapping can also be used to prevent further swelling. The major concern with this infection is if it damages the tissue and affects the lymph system’s ability to draw out fluid and return it to circulation. If this occurs, the leg will always be larger than normal and will be susceptible to infection with any minor break in the skin. If your horse’s leg is even moderately swollen, don’t wait but call your veterinarian right away.