Horses engaged in athletic pursuits are at risk for skeletal damage. Bucked shins, bone chips, and fractures are commonplace in the world of high-performance horses, but other problems, like bone bruises, are less ordinary.
A bone bruise is an injury to subchondral bone, which is the bone layer that abuts cartilage in weight-bearing joints. Subchondral bone is rife with blood vessels, which not only ferry oxygen and nutrients to the bone but also to the underlying cartilage. Bone bruises are usually brought on by repetitive trauma and subsequent insult during racing or training. Inflammation associated with the injury causes degeneration of healthy subchondral bone, thus compromising its strength and integrity.
“In response to traumatic insult, the skeleton repairs itself by removing damaged bone and replacing it with more bone. Changes in bone are expected in response to training, but the difficulty lies in the fact that bones can only repair, and thus strengthen, themselves so quickly,” explained Laura Petroski, B.V.M.S., veterinarian at Kentucky Equine Research (KER).
“If insufficient time is afforded for healing, the remodeling process is disturbed, and over time the subchondral bone thickens and becomes less flexible. Repeated overloading of diseased bone results in bone bruises and pain. Damage may also occur to corresponding joint cartilage, which may compound soundness issues. As most horse owners know, destruction of cartilage leads to the development of degenerative joint disease, or arthritis,” she continued.
Bone bruises are most often diagnosed in horses trained at high intensity, such as Thoroughbreds and Standardbreds, and problems manifest primarily in the fetlocks. High-impact work exposes the horse to the traumatic forces needed for a bone to become denser and then subsequently bruise. In Thoroughbreds, bone bruises usually occur in the front fetlocks, while in Standardbreds they affect hind fetlocks more frequently. Bone bruises are observed occasionally in knees. Subchondral bone disease at any site can put horses at risk for fracture.
Horses usually present as unsound, though the lameness might range from mild to severe. “Complaints of poor performance, where the horse is suddenly not performing at the same level, are also typical and alert owners and veterinarians of a problem. The pain is localized to the affected site by using nerve blocks, flexion tests, and palpation. At that point, we recommend radiography or advanced imaging,” said Petroski.
“In the past, veterinarians have diagnosed this disease using radiography; however, we’ve learned changes noted on radiograph tend to be permanent changes and the disease is quite advanced at that stage,” she remarked.
Today, veterinarians rely on nuclear bone scintigraphy and MRI to reveal early signs of this disease. “This technology has been revolutionary when it comes to diagnosing, treating, and managing these horses properly. The earlier the treatment begins, the better our prognosis for returning the horse to full work.”
Treatment of bone bruises involves primarily rest and recovery. Unlike certain soft tissue injuries, veterinarians often suggest that horses with bone bruises be turned out into a small field for several months and allowed to move.
Blood flow to this area is important for tissue healing, and free-choice exercise in a small paddock is encouraged. Any forced exercise is discouraged. Other treatments include anti-inflammatory drugs, intra-articular injection of steroids, pharmaceuticals to promote bone repair, and surgery. These treatments are not universal to all horses with bone bruises, so treatment plans are devised on a case-by-case basis.
Nutrition of horses with bone bruises begins with a well-fortified diet. Many horses with skeletal damage are involved in intense athletic pursuits, so they are likely fed high-quality forages and concentrates. Calcium is a critical nutrient in any well-fortified diet, but especially those of young athletes.
“While we cannot prevent bones from laying down more calcium, it would be wise to protect other bones from becoming weaker due to insufficient calcium intakes. The body tends to take calcium from other bones if there is not enough calcium available in the blood. The loss of calcium from other bones changes the structure of that bone and weakens it,” said Petroski.
Because young, growing racehorses are often affected by bone bruises, demand for calcium within the body is high. Once a bone bruise is diagnosed and rest instituted, the diet should be adjusted appropriately to reflect the change in workload, though a well-balanced diet is important at all times. Further, targeted nutritional supplementation may help these horses.
“Triacton, a triple-action supplement designed by equine nutritionists, may be useful in these situations,” said Catherine Whitehouse, M.S., a nutritionist for KER. Triacton contains a novel source of highly digestible calcium and other bone-building nutrients to increase bone quality. “In addition to its skeletal benefits, Triacton also provides buffering for gastric and hindgut health,” she continued.
In addition to promoting bone health, young horses in training benefit from receiving Synovate HA, a high-molecular weight sodium hyaluronate that has anti-inflammatory, lubricating, and shock absorbing properties for optimal joint health.
Injuries cause stress in horses, which predisposes them to gastric ulcers and possibly hindgut upset, explained Petroski. This may be further exacerbated by a change in routine as treatment protocols are established. “I believe in preventing problems rather than treating them, if possible. Because we know that changes in routine will often lead to distress and compromise to the gastrointestinal tract, especially in young horses, it is best to be proactive in protecting the stomach and hindgut.”
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