THE SPECTRUM OF SHOULDER INSTABILITY
There is considerable variability among people in terms of their shoulder anatomy and function. Because of this, we all find ourselves somewhere on the spectrum of shoulder stability. On one extreme, we find people with “tight” shoulders that are highly resistant to dislocating, but with limited shoulder motion and often some degree of pain, depending on their activities. On the other extreme, we find people with “loose,” highly mobile, unstable shoulders, some of whom can dislocate their joints on command with minimal to no pain. And, regardless of where we begin on that spectrum, injuries, life events, aging, deconditioning, and other medical conditions can push us further in either direction.
For those patients who find themselves closer to the unstable end of the spectrum, but have not yet experienced a full dislocation, we often call this micro-instability. Patients who have experienced a shoulder dislocation are often broadly grouped into one of two categorizes.
The first main type of instability typically involves a traumatic event in an individual with normal tissue elasticity, resulting in a single-direction dislocation and tearing of soft tissue structures. This is particularly common in younger patients and is often treated with surgery. For example, in the most common scenario, the ball dislocates in an anteroinferior direction, resulting in tearing of the anteroinferior portion of the labrum, referred to as a Bankart lesion.
The second main category of shoulder instability is multidirectional. These are patients who have loose/elastic tissues due to their own genetics, resulting in capsular ligaments that simply stretch out over time. Because of the instrinsic qualities of the collagen in these types of patients, the stretched capsular structures typically remain attached and tearing of the labrum may not occur. These patients may experience dislocations in multiple directions and often involving both shoulders as a result of minimal or no trauma (e.g. when sleeping, reaching, etc.). Although surgery can become necessary, most patients respond well to rehabilitation.
Nels Sampatacos, MD
Orthopedic Surgeon and Sports Medicine Specialist
