Acromioclavicular joint injury
If you live on the Front Range of Colorado you probably know at least a few mountain bikers, if you are not one yourself. And if you talk to mountain bikers about their injuries you will start to see a trend: lots of collarbone injuries. Falling over the handlebars -- a right of passage among mountain bikers -- is a common culprit for collarbone injuries. The most common collarbone injury amongst mountain bikers is an AC joint separation.
AC joint separation occurs most commonly when a downward force is placed on the shoulder or upper arm, tractioning the arm from the body (including the clavicle). This occurs in biking with a crash onto the shoulder, or in football when a player takes a strong hit to the top of the shoulder. The joint at the end of the clavicle -- the acromioclavicular joint -- takes the most stress in this injury and the ligaments that hold the joint in place can tear.
Degree of injury
AC joint separations are graded from I to VI depending on the type and severity of separation. In a Grade I sprain, the ligaments are minimally torn and normal activity can usually resume pain-free within a few weeks. Grade II includes more ligament tearing and can result in a small bump deformity on the top of the shoulder, but usually heals within two months without functional deficit. Grade III sprains involve a complete tear of the ligaments and visible “step deformity” over the top of the shoulder. The “piano key sign” occurs with this grade of separation where you can push down on the raised collarbone and it will pop back up like a piano key. Grade III injuries can be treated surgically, especially if someone is concerned with their physical appearance, however, functional outcomes are roughly equal between those who undergo surgery or not. Grade IV-VI AC joint separations are rare, but more serious, and require surgery.
So what can you do if you separate your AC joint? In the short term you want to let it heal without injuring it again. Icing it is likely beneficial for at least the first week and taping over the joint with kinesiotape or a more rigid tape can help give a feeling of stability for a few months. Avoiding high contact sports until it’s completely healed will help prevent a worsening of the joint separation. As it starts to feel pain free, the strengthening phase begins. Because of the separation of the joint and tearing or stretching of ligaments, the shoulder joint will be inherently less stable; using muscular strength to support the AC joint becomes more important. Strengthening exercises include rotator cuff, shoulder blade, upper trap (top of shoulder), and chest strengthening to provide support all around the joint. A physical therapist can guide this strengthening phase over the course of a few weeks to a few months, depending on the severity of injury
As a rule of thumb, if there is a visible bump on the shoulder more than a quarter inch and/or pain lasting more than 2 weeks it is advised to get the injury evaluated by a physician or physical therapist to help grade the injury and guide recovery. If pain is severe or the separation is more than a half an inch then immediate medical attention is advised as surgical treatment for this injury, if needed, can be time sensitive.