Bucked Shins in Horses

Bucked shins, a painful, acute periostitis on the dorsal surface of the third metacarpal bone in horses, is part of the disease complex known as dorsal metacarpal disease. It occurs exclusively in racehorses—most often in the forelimbs of young Thoroughbreds (2-year-olds) in training and racing, and less commonly in Standardbreds and Quarter Horses.

Bucked shins can occur bilaterally and usually occurs sequentially, with the left leg affected first in most cases, because horses in North America are trained and raced in a counterclockwise direction.

Bucked shins can be the result of high-strain cyclical fatigue caused by excessive compression on a bone that has not remodeled enough to tolerate the stress placed on it. Stressed bone forms a new layer of bone at the point of stress. This new bone is weaker, and rapid bone formation causes the periosteum to become elevated and inflamed, and sometimes to develop dorsal cortical stress fractures (see stress fracture image).

Dorsal cortical stress fracture, third metacarpus, radiograph, horse

Image

Courtesy of Dr. Matthew T. Brokken.

Diagnosis of bucked shins is typically based on clinical examination and history (soreness over the dorsal aspect of the cannon bone, soreness after high-speed work or the horse's first race, or soreness the day after).

Radiographic examination determines the amount of periosteal reaction and whether dorsal cortical stress fractures are present.

Treatment of bucked shins typically consists of altering the training schedule to short bursts of speed work 2–3 times per week. Until the soreness and inflammation resolve, rest from training is also important.

The acute inflammation of bucked shins can be relieved by anti-inflammatory analgesics and application of cold packs. Screw placement, with or without osteostixis, carried out under general anesthesia or under standing sedation with local anesthesia, is the method of choice to treat radiographically visible stress fractures.