The most common shoulder injury from falling off a bike has to be shoulder separation. This is when the three parts of the shoulder separate. The three bones in the shoulder comprise of the collar bone, shoulder blade and the arm bone. It is usually the arm bone that separates from the shoulder bone and the shoulder blade, as it is attached with the help of ligament fibres. Since it is a joint that is held in place with the help of ligament fibres , in the event of an accident the arm is usually stretched to the point of breaking. It also leads to frequent dislocation of the arm.