There is much to enjoy for a new Thoroughbred racing fan. There’s the beauty of the animals, the thrill of watching them move, and the exhilarating feeling of outwitting the other horse players and collecting a bet.

But there’s a cold fact about the sport that can be hard for fans to accept, and impossible for critics: Sometimes a horse gets hurt, and sometimes it’s put down, often on the track.

Earlier this month, seven horses died at Churchill Downs ahead of the Kentucky Derby, including four that broke down while racing or training. And National Treasure’s, trained by Bob Baffert, victory in the Preakness was marred by the collapse and euthanasia of another Baffert racehorse earlier that day at Pimlico Race Course.

People who are opposed to horse racing on principle often point to such facts when presenting their case. Even for racing fans, the unsettling reality of breakdowns can raise the question: Does something as seemingly simple as a broken leg have to kill a horse? The unfortunate answer, vets say, is usually yes.

Horses are just different from many animals, even other equines. “They can run very fast,” said Dr. Scott E. Palmer, equine medical director for the New York State Gaming Commission. “And because they’re about 1,100 pounds, the forces acting on their legs are really profound.”

Palmer continued: “All his muscles are up. When you go down to the lower leg, there is literally skin, bone, tendons, blood vessels, and nerves. If something breaks, circulation to the area can easily be compromised by the injury.”

As a result, horses are vulnerable to breaking their legs; it happens running on the racetrack, or running in a pasture, or kicking in a barn door. The problem is that it is very difficult to heal a broken leg on a horse.

Breaks in horses can also be much more severe than in humans or other mammals, due to their weight and the fragility of their legs. “Because of the high-energy impact, the horse can break that bone, more than just a crack, making repair much less likely,” Palmer said.

To fix a broken bone in any animal, the break must be immobilized. But immobilizing a horse brings a number of challenges. Horses are restless and skittish. Thoroughbreds are bred to race. Keeping them in one place for a long period of time is difficult.

Horses also spend most of their time on all fours, even when they are sleeping. So all four legs support its weight. If suddenly three legs have to carry that weight, the healthy legs can quickly develop problems.

Most common and dangerous, horses can contract laminitis, a painful condition that develops in the tissue between the hoof and bone. “The hoof is attached to the bone by organic fasteners like a Velcro system,” Palmer said. “If those hooks swell, they disengage. That’s impossible to fix.”

The whole treatment experience can bring severe pain to a horse who, of course, cannot understand what is going on in the same way that a human undergoing painful treatment would.

The pain for the horse is the consideration “No. 1, No. 2 and No. 3,” Palmer said.

Laminitis brings “incredible pain,” he said. “They can’t stand on that leg. Now you have a horse with a broken leg and it can’t stand on the second one.”

Horses cannot simply lie down for extended periods to avoid putting weight on their legs. Lying down for more than a few hours will cause muscle damage, restricted blood flow, and pooling of blood in the lungs.

Any elaborate or unusual process to try to repair a severely broken bone can cost thousands of dollars. Few horse owners are willing to spend that kind of money on a painful treatment process that might not work and probably won’t get the horse back on the racetrack. Euthanasia is the unfortunate choice most of the time.

When 2006 Kentucky Derby winner Barbaro broke his leg in the Preakness two weeks later, his owners, Roy and Gretchen Jackson, decided to try to save him.

His injury was serious: the leg bone was broken into 20 pieces. She had five hours of surgery to insert 27 pins and a stainless steel plate.

Palmer was on the scene the day of the injury. “I said, ‘The fracture is horrible, but none of the wounds went through the skin. Therefore, I believe that surgery is possible.’ Honestly, I thought it was the best chance he had to survive.”

Two months after his surgery, Barbaro developed laminitis, which required the removal of most of one hoof. He then had a few good months. But the hoof didn’t grow back properly, leading to another procedure. He bruised his foot and further operations followed. Complications led to laminitis in two more extremities, and Barbaro’s distress increased significantly.

“We just got to a point where it was going to be difficult for him to continue without pain,” Roy Jackson said. In the end, the extraordinary efforts extended his life by only eight months.

“From a purely surgical perspective, it was extremely unsatisfactory because it didn’t make it,” Dr. Dean W. Richardson, the surgeon, said at the time. “Professionally, I think we did the best we could.”

The stunning Ruffian filly in 1975 had 12 hours of surgery following a bad break. Upon awakening from her, she began to squirm in her position, causing another rupture and leading to her being euthanized.

If euthanasia is the only option, the horse is sedated and a barbiturate solution is then administered, usually behind a screen to block the view of bystanders.

Advances have been made in recent decades in the treatment of horses, including the development of better antibiotics and the aluminum splint and improvements in the understanding of laminitis.

There have also been improvements in prevention which, given the unusual anatomy of the horse, may be the most promising way forward.

After a series of horse deaths at Aqueduct in 2011 and 2012, Palmer and others made recommendations, including improving the racing surface, changing the claim and bag rules, and strengthening drug regulation. Those have helped the number of racing deaths. get down and stay down.

Palmer is hopeful of Fitbit-like devices: biometric sensors that can detect horses with gaits that could cause injury before those injuries happen. A test at Saratoga Race Course last year was promising, he said.

But the challenge of caring for the horses is likely to remain forever. Palmer said of the difficulties of the surgery: “We have to reattach a broken leg with screws and plates, and they have to be able to stand on it immediately after surgery. That is a huge challenge.”