Viewers of the 2006 Preakness horse race received a very disturbing reminder of the dangers of a broken leg for horses. A heavily-favored horse named Barbaro took a misstep shortly after leaving the starting gate, causing his jockey to pull him out of the race immediately. Television cameras caught the dramatic events as they unfolded, from the emergency treatment on the track to the loading of Barbaro onto a specialized ambulance for horses. All initial signs pointed to a broken leg, which is usually considered a fatal complication in horses.

But why is a broken leg so dangerous for horses? There are a number of reasons why owners choose to euthanize horses who suffer severe injuries to their legs. Primarily, it's a quality of life issue for the injured horse, since a broken leg can take months to heal even under the best of circumstances.

Horses do not react to crippling injuries the same way their human owners might. A person with a broken leg can remain immobile or in traction for weeks following the injury. A horse, on the other hand, is naturally compelled to move freely at all times. The idea of extended bedrest is completely counterintuitive to a horse bred for motion.

When a horse suffers a broken leg, the treatment regimen is often complicated and expensive. Only the youngest and healthiest horses are considered for the most aggressive therapies, such as cold laser treatments, therapeutic ultrasound or active magnetic field therapy. Even if a horse can be tranquilized while a broken leg heals, it cannot survive the weeks or months of relative immobility. A horse feeling trapped in a cramped stall tends to tap dance, which can easily aggravate the original broken leg.

Even using a sling to reduce stress on the horse's broken leg has a number of drawbacks. Slings are generally used to load a sick horse into a waiting ambulance or for other short-term transportation needs. A horse recovering from a broken leg cannot remain in a sling for weeks at a time. Constant skin chafing often causes dangerous sores to develop.

A horse's muscular structure requires the legs to bear a significant amount of weight. If the horse is suspended from a sling for an extended period, the leg muscles soon begin to atrophy and weaken. A horse suffering from multiple fractures, such as Barbaro, must use a brace to allow the broken leg to continue to bear weight.

There is also a strong possibility of opportunistic infections developing around a horse's broken leg. If surgical plates or braces are implanted around the affected bones, there is always the risk that the skin may not heal properly. Horses are also prone to a infection of the nail called laminitis. Treatment for other health problems may be especially difficult when the horse already suffers from a broken leg.

The idea of euthanizing a horse because of a broken leg may seem disturbing to some, but the decision is usually reached only after an extensive examination and conference with a qualified veterinarian. Horse owners must balance the potential success of treatment and the horse's potential quality of life. It's never an easy decision to put down a suffering animal, but certain injuries cannot always be treated without causing even more stress for the animal. A broken leg is not the automatic death sentence it once was, but owners need to understand all of the ramifications of an aggressive treatment program.