Illustration shows the normal bony anatomy of the shoulder area. The red arrow points to the joint that comes apart in a shoulder separation injury.
If the force is severe enough, the ligaments attaching to the underside of the clavicle are torn. This causes the separation of the collarbone and the shoulder blade. The shoulder blade (scapula) actually moves downward from the weight of the arm. This creates a bump or bulge above the shoulder.
The injury can range from a mild sprain without a bump to a complete disruption with a very large bump. Good pain-free function often returns even with a very large bump. The greater the deformity, the longer it takes for pain-free function to return.
A mild shoulder separation involves a sprain of the AC ligament that does not move the collarbone and looks normal on X-rays.
A more serious injury tears the AC ligament and sprains or slightly tears the coracoclavicular (CC) ligament, putting the collarbone out of alignment to some extent with a smaller bump.
The most severe shoulder separation completely tears both the AC and CC ligaments and puts the AC joint noticeably out of position, with a larger bump.
This figure shows the intact ligaments around the acromioclavicular joint. The red arrow points to the ligaments that are around the joint itself. The gray arrow points out the important stabilizing ligaments underneath the collarbone.
Nonsurgical treatments, such as a sling, cold packs, and medications can often help manage the pain. Rarely, a doctor may use more complicated supports to help lessen AC joint motion and pain.
It is often worthwhile to wait and see if reasonable function returns without surgical treatment. Most patients, even with very severe injuries, are often managed effectively without surgery.
Surgery can be considered if pain persists or the deformity is severe. A surgeon might recommend trimming back the end of the collarbone so that it does not rub against the shoulder blade bone (acromion).
Where there is significant deformity, reconstructing the ligaments that attach to the underside of the collarbone is helpful. This type of surgery works well even if it is done long after the problem started. These operations can be done arthroscopically or open, with a plate or without. Sometimes, if a plate is used to assist with the surgery, it is usually removed after healing of the shoulder separation.