broken bone is usually the result of an accident, such as falling down from a high place, or being hit by a monster. Cats most often break their legs, and while medicine cats try to bind the bone with cobwebs, the injury usually results in the cat remaining crippled for the rest of their life. The only cat known to fully recover after breaking a leg was cinderheart.
A more severe injury is when a cat breaks their backbone. This results in the cat being unable to feel or move parts of their body. If the break is bad enough the cat will be killed on or shortly after impact. briarlight broke her backbone, and as a result, her back legs no longer function and she has no control over her bowel movements. WildFur also broke his backbone, and since he only sat in his nest all day, he got fluid in his lungs and eventually died from not exercising.