Shoulder Instability


The shoulder joint is made up of bones held in place by muscles, tendons, and ligaments. Tendons are tough cords of tissue that hold the shoulder muscles to bones, and help the muscles move the shoulder. Ligaments hold the three shoulder bones to each other and help make the shoulder joint stable.

Anyone can experience a shoulder problem – men, women, children, and people from all races and ethnic backgrounds, although shoulder issues are most commonly seen in people older than 60 years old. As you might suspect, shoulder problems also commonly occur in the athlete.

A shoulder issue that our physicians commonly see at Orthopedic Specialists of Seattle is shoulder instability, a condition where the structures that surround the glenohumeral (shoulder) joint do not work to secure the ball within its socket. If the joint is too loose, is may slide partially out of place, a condition called shoulder subluxation. If the joint comes completely out of place, it’s called a shoulder dislocation.

Athletes can be prone to weakened or injured shoulder ligaments. Shoulder instability may occur as a result of previous dislocations, but it can also occur from repetitive movements such as pitching, throwing or serving. Athletes can have such severe instability that they may routinely dislocate their shoulder throughout a sports season

Types of Instability

? Anterior Instability is the most common type of shoulder instability. In this case, the most vulnerable positions are rotating the hand and arm out and back, and away from the body.

? Posterior Instability is less common. Athletes or patients sustaining traumatic forces may experience posterior instability. However, the most common mechanism for posterior instability is dramatic involuntary muscle contraction by the shoulder (e.g. seizure).

? Multi-directional Instability most commonly occurs when the rotator cuff muscles are weak or not functioning properly. Athletes or those who perform repetitive overhead movements are prone to multi-directional instability.

How do you know if you’re experiencing shoulder instability?

Some situations are obvious, such as feeling pain after a shoulder injury, or experiencing a shoulder dislocation. If your shoulder joint is unstable, you might have a persistent sensation of the shoulder feeling lose. You may be able to actually feel that you’re about to dislocate your shoulder.


There is a wide range of treatment, depending on the nature and degree of instability. The age of the patient is also a factor, as younger patients are more likely to have chronic instability. Many patients can be treated with physical therapy, although some will require surgery.