A knee fracture is a break in one or more of the knee bones, usually the kneecap. The ends of the thighbone and shinbone where they meet can also be fractured. Sometimes, the bone(s) can be broken into several pieces or shatter.
Many knee fractures are caused by high-energy accidents, like car accidents or falling from a tall ladder. Men are twice as likely as women to fracture the kneecap. Thighbone fractures are common in people who are older or have weak bones.