What is shoulder instability?
Shoulder instability is when a person suffers from a shoulder dislocation or the feeling of the shoulder “slipping out” or feeling “unstable.” This can occur from a traumatic injury such as falling or contact during a sporting event. A smaller percentage of people have atraumatic or “multi-directional” instability where the shoulder feels unstable and slips in and out of joint in the absence of a previous shoulder injury or dislocation. Chronic shoulder instability is when the shoulder has dislocated multiple times after the initial injury.
Why does a shoulder become unstable and dislocate?
The shoulder is stabilized by the complex anatomy surrounding the joint. This includes the joint capsule and ligaments (lining of the joint), the surrounding musculature (rotator cuff), and the bony shape of the joint itself. Injury or an abnormality of any one of these three components can cause a shoulder to be unstable. When a shoulder dislocates, the most common location of injury is at the labrum – a thickened portion of the joint capsule that serves as the attachment point of the strong stabilizing ligaments to the shoulder socket, or glenoid. Occasionally a piece of the socket itself can fracture during a dislocation, often resulting in a higher degree of shoulder instability. Less commonly, and typically in older individuals, tears of the rotator cuff or fractures of the ball portion of the joint (humerus) can occur after a dislocation and lead to further instability. Variations and combinations of all three components are often seen in patients dealing with a chronically unstable shoulder. Most patients with traumatic shoulder instability know the exact position where their shoulder is in danger of slipping out, and avoid this position at all costs.
In contrast to a discrete and traumatic shoulder dislocation, patients with multi-directional instability often describe a history and ability to slip their shoulder out of joint at will. They have symptoms of frequent “shifting” of the joint in many different positions. The cause of this type of instability is less understood, but likely is caused by a slightly more “stretchy” joint capsule that is genetic in origin. Patients often describe themselves as double-jointed and extremely flexible.
How is shoulder instability treated?
The optimal treatment for an unstable shoulder varies depending on your age, activity level, the structural injury to the shoulder, as well as the degree of instability. This becomes much less clear for patients with multi-directional instability patterns.
In general, the younger you are at the time of your first dislocation, the higher the risk of having more dislocations. Similarly, the higher your activity level, the higher your risk of re-dislocating. This is most accurate for contact and overhead athletes. The third group at high-risk of re-dislocation are patients with large amounts of bone loss or bony injury as part of the dislocation. These individuals lack the appropriate bony structure to support the shoulder and can continue to be unstable even after a typical arthroscopic stabilization procedure.
The first-line treatment for most shoulder dislocations consists of a brief period of rest and immobilization. This is followed with early, supervised physical therapy to work on regaining pain-free motion of the shoulder with a step-wise progression back to full activity. Many patients who are not in a high-risk category can recover uneventfully without continuing feelings of instability.
For higher-risk patients - those under the age of 23 involved in collision sports, those with bone loss on either the ball or socket (or both), and those who have re-dislocated after surgical treatment, we will often recommend surgery. The type of surgery depends on the structures involved.
The most common treatment is through a minimally-invasive arthroscopic stabilization, also known as a Bankart repair (referring to the most common injury of the labrum on the front of the shoulder, widely known as a Bankart tear). Through the use of the arthroscope, we are able to repair and tighten he torn ligaments, as well as smaller bony fracture fragments through three or four small incisions around the shoulder. Larger bony defects can sometimes be treated arthroscopically; however, recent research suggests that patients missing more than 20-25% of the bone on the socket should have an open (incision on the front of the shoulder) coracoid transfer or bone graft. This is a much bigger surgery that involves taking a piece of bone from one part of the shoulder (the coracoid), and attaching it to the area of the socket that is lacking bone. Failed arthroscopic stabilization procedures are often treated in this way as well.
For patients with multi-directional instability, the mainstay of treatment is rehab, rehab, rehab - and more rehab. The vast majority of patients with this pattern of instability will recover fully with strengthening of the surrounding musculature and improved control of the stabilizers of the shoulder blade. If exhaustive physical therapy has failed, surgical tightening of the loose capsule can occasionally be attempted with caution – outcomes are less predictable with this instability pattern.
Do I need surgery?
If you dislocated your shoulder and continue to have episodes of instability and slipping of the joint that affects your quality of life and ability to remain healthy, active, and productive, we would recommend a surgical evaluation. Again, not everyone with a shoulder dislocation needs surgery; but patients with persistent instability and those at high-risk of re-dislocation are often recommended some type of surgical stabilization.
For further, in-depth information regarding shoulder dislocations and instability, we have provided links to the American Academy of Orthopaedic Surgeons patient portal, as well as the University of Washington’s Department of Orthopaedic Surgery and Sports Medicine website.
For more information, please visit the following links:
AAOS Orthoinfo Chronic Shoulder Instability
UW Traumatic Shoulder Instability
UW Atraumatic (multi-directional) Shoulder Instability