A fat embolism is a type of embolism that is often (but not always) cause by physical trauma. Fat emboli can occur whenever there is a chance for fat to enter the circulatory system, such as during surgery. One of the more common scenarios is the fatty marrow entering the circulation after a fracture to a large long bone, such as the femur, or after surgery on this bone, which then lodges in the lung, causing inflammation of the lung and pulmonary failure. Blood clots that travel to the lung are usually known simply as "pulmonary emboli".