When it comes to the legs of a horse, it is the ones in the lower legs that are most susceptible. Usually, a bone breakage occurs when a horse falls: the weight and momentum behind such falls can easily snap even their strong bones. There are certain bones very likely to break:
The Pedal Bone: This bone usually breaks when a horse lands on an uneven surface, or in some cases when it kicks a wall. As long as the coffin joint doesn’t break along with it, it can usually heal relatively easily. If the coffin joint is involved, surgical intervention will be needed.
The Pastern Bone: The pastern bone, when it breaks, often occurs in a way where it extends down from the fetlock joint. Depending on the severity of the break, mere bandaging and rest could be enough to heal, but compound fractures here will limit future potential.
Sesamoid Bones: These are two small bones near the back of the fetlock joint, and they support ligaments at the rear of the pastern and cannon bone. As part of the suspensory apparatus that allows the horse to hold its weight, breaking these can often result in permanent lameness, leading a horse to be euthanized.
The Cannon Bone: These fractures often extend into the fetlock joint. Breaking the cannon bone is very similar to breaking the pastern bone, and you can expect similar treatments and prognoses based on the severity of the break.
The Knee Joint: Knee fractures are usually chips, rather than full breaks. These can result in pain and inflammation but rarely incapacitate a horse. However, even in such cases, surgery can often be necessary.