An avulsion fracture happens when which structure pulls off a piece of bone?

An avulsion fracture occurs when a piece of bone is pulled away by a structure that is attached to it. This can happen with muscles, tendons, or ligaments, which all have the potential to exert enough force to pull a small fragment of bone off when they contract or are suddenly stretched.

Muscles are attached to bones via tendons, and when a muscle contracts excessively, it can lead to an avulsion fracture at the point where the tendon is attached. Similarly, ligaments connect bone to bone at joints, and if a ligament experiences a strong enough force, it can also cause an avulsion fracture by pulling a piece of bone at its attachment site.

Since all three structures—muscles, tendons, and ligaments—can independently lead to an avulsion fracture under certain conditions, it is accurate to say that an avulsion fracture can occur because of any of these structures. Therefore, the answer encompasses all three types of connective tissues that can be involved in this injury mechanism.