Back in the Wild West, a horse with a broken leg may have spent its last seconds staring at the barrel of a cowboy’s gun. Horses are often shot after a broken leg because they have a very small chance of a successful recovery. Even today, horses often die after breaking their legs.
In the video, the racing horse accidentally tripped over an obstacle, which is a tire, causing both it and the person above to fall. Unfortunately, after that collision the horse broke its left leg making it unable to walk

Here’s why: Horse legs are hard to heal due to a combination of factors. Their legs must absorb considerable shock as their muscular bodies gallop at high speed. Horses engage in a lot of physical activity, and the consequences of this behavior can eventually lead to degenerated leg bones and an increased likelihood of falls.

Another thing to consider is how many leg bones a horse has. Of the 205 bones that make up the entire horse’s body, 80 are located in the leg [source: O’Brien and Sellnow]. The complex system of joints, bones, ligaments, tendons, cartilage, lubricants, membranes, and hooves that contribute to a horse’s incredible speed may also be responsible for its decline. Furthermore, 58 percent of a horse’s weight is on its front legs — which is why most horse injuries occur there [source: Swann Equine Osteopathy].

Many problems can affect a horse’s legs, such as inflammation, osteoarthritis, joint diseases and of course fractures. The recovery process is even more complicated because horses cannot lie down during their recovery. Horses are programmed to stay upright most of the time – even when they’re asleep. As a predator, they must be ready to run away as quickly as possible, which is why horses are on tiptoe (or more precisely, hoofs) [source: Tikkanen].

However, assisted suicide is not always a certainty. New surgical techniques and technologies present options that were once elusive in such a situation.+