The collarbone, or clavicle, is the connection between your axial skeleton, or your trunk, and your body. It runs from the middle of your chest to your shoulder and connects your shoulder blade and your shoulder to the anterior chest wall. The most common injuries are fractures to the clavicle or injuries to the joints on either end of the clavicle. One of those joints is the sternoclavicular joint, which is on the side closest to the chest, and the other is the acromioclavicular joint, which is on the shoulder end. An injury to this joint is commonly referred to as a shoulder separation.
Shoulder separations are very common in sports like football and hockey.
The two mechanisms for injury are direct and indirect injuries. Direct injuries, as their name suggests, are caused by direct blows to the shoulder, particularly from the top of the shoulder. A common example would be going over the handlebars of your bike and landing on your shoulder. Indirect injuries are caused by falling on an outstretched hand or a blow to the outside of the shoulder, which pushes the shoulder into the chest and compresses the clavicle, causing it to be injured. Complete tears in active populations need to be surgically repaired.