What does it mean when a horse bucks its shins?

Question

What does it mean when a horse bucks its shins?

Answer 1

To Buck or Not to Buck (Shins)

The Horsemen's Journal - Winter 2006

Horsemen have been battling bucked shins since we first began asking the question “Who’s horse is faster?” And the cause has always been the same – too fast, too soon.

“They (bucked shins) are a response of the cannon bone to microfractures,” explained Dr. Brian Nielsen of Michigan State University.

As a young Thoroughbred begins its race training, the cannon bone is constantly modeling (growing) in order to handle the demands being placed upon it.

“When an animal exercises,” commented Nielsen, “the bone bends as weight is put on it. If the load placed on it is too great, or if the number of times it is bent is excessive, damage to the bone can occur. Fortunately, bone has the ability to repair itself if given enough time.”

Bone modeling only seems to occur in the juvenile skeleton as compared to bone remodeling which occurs throughout life, Nielson explained. “Bone modeling is either the net deposition or resorption of bone, while remodeling is the resorption followed by deposition. Since modeling occurs in the juvenile skeleton, the young horse is much more susceptible to bone loss when disuse of the bone occurs.”

Speed is a necessary component in order to build strong cannon bones. But there exists a fine line between the right amount of speed to strengthen the bone and too much speed, which can harm.

“It appears that bucked shins is an inflammatory response to the damage that is occurring (during training),” explained Nielson.

Because more new bone is deposited on the surface of the cannon bone when an animal bucks its shins, many trainers subscribe to the old adage, “buck ‘em good,” in the belief that the bone becomes stronger in response to the inflammation. In a study published by Dr. David N. Nunamaker, Jacques Jenny Professor of Orthopedic Surgery at the University of Pennsylvania’s New Bolton Center, it was determined that bucked shins generally occurred in Thoroughbred racehorses during the first year of training – usually as a two-year-old. Horses that had been brought along slowly – what trainers refer to as “putting a bottom” into them – before being asked for speed were more likely to buck their shins once speed work began.

“It seems that providing some stimuli to the bone, either through turn-out or through short-programmed works, is the best way to prevent the problem or at least minimize the occurrence of it,” Nielsen asserted.

Researchers have shown that when young horses have been put into stalls without any access to sprinting, the mineral content of their cannon bones is reduced. Add to that the lack of high-speed work during the first few months of training, and the scenario has been set for bucked shins.

“Adding short sprints to the early long-slow distance part of training as a method to prevent bucked shins seems to be very successful,” Nielson commented.

As anecdotal evidence of the stalling versus mineral content argument, Nielsen talked with a trainer of National Hunt horses while on a visit to Northern Ireland. According to Nielson, “One trainer informed me that these National Hunt horses have been known to buck their shins as late as when they are five-year-olds. After questioning him further, it turns out that these horses are stalled for weaning, then kept in stalls all winter long so as to not tear up the pastures. This seems to suggest that the long term confinement rearing of horses may predispose them to problems such as this (bucked shins) even later in life.”

Nielson explained that as for treatment of bucked shins, the trainer may just need to back off on speed work. Even if a horse has a “shin,” the slow gallops can still be incorporated into the training. The problem lies in not letting them heal sufficiently before asking for more speed.

Nielsen suggests that the horse with bucked shins be kept in light training or given turn-out time. Because of the bone mineral density loss association, he does not like to see a horse put on complete stall rest. He asserted that “just 15 or 20 minutes a day turn-out” can be enough to stave off bone loss.

If a trainer is uncertain of whether or not an animal has recovered, Nielsen suggests he let the animal tell him. An animal’s attitude can tell you a lot, explained Nielson. If the horse begins showing signs of not wanting to train (i.e. fighting saddling, refusing to leave the barn, etc.), then it probably is not recovered.

“If they’re hurting, then they aren’t enjoying what they’re doing,” Nielson added. “The pain is there for a reason.” Additionally, the trainer will want to palpate the shin for any signs of tenderness. According to Nielson, “By using this combination, a trainer can determine when to start bringing the animal back.”

Many trainers will opt to blister or pinfire a horse’s shins. “This is a pro-active approach,” said Nielsen. He went on to explain, however, that it has no therapeutic value in treating bucked shins. What it does do is force the trainer to give the horse enough time off to completely heal.

“If it (pinfiring and blistering) really worked, you’d do it in humans,” said Nielsen.

Bucked shins are not a career threatening injury – at least not in and of themselves. But Nunamaker’s research has shown a significant relationship between bucked shins and a career ending injury.

“From our observations after questioning clients, it appears that almost all the animals that develop saucer fractures had previously bucked their shins,” he reported. “If this is true, the adage ‘buck ‘em good’ will lose its status.”

Neilsen sums up his advice to trainers, “one should always try to avoid having a horse buck its shins.”

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