1. Multidirectional Instability Involves Anterior, Posterior and Inferior
Usually shoulder instability is anterior, and most shoulder dislocations are out the front. However, the shoulder can also be partially dislocated, or sublux, out the back (posterior) and down (inferior). When the shoulder is loose in multiple directions, this is termed multidirectional instability (MDI).
2. Repetitive Stretching and Extreme Flexibility Indicate MDI
Oftentimes, people with multidirectional instability of the shoulder also have signs of generalized ligamentous laxity. Their fingers bend backwards, and they can bend their thumb down and touch their forearms. They can hyperextend their elbows, and have loose kneecaps, or hypermobile patellae. Overall, their collagen, or connective tissue of the joints, is simply more stretchy. Because the shoulder is an inherently unstable joint, loose collagen makes it less stable.
Another cause of MDI is repetitive stretching of the tissues. This occurs in athletes such as swimmers, gymnasts, volleyball players and throwers. Because these athletes place their joints in extreme positions, it stretches out the shoulder capsule over time. Of course, their extra motion may be what makes them great athletes in the first place.
3. Bilateral MDI Is Common
Because this is a result of loose connective tissue, it usually happens in both shoulders. However, even though both shoulders may be loose, they may not cause pain. In other words, people may have laxity, or looseness, but not necessarily instability or pain due to the looseness.
4. Physical Therapy Improves Most Cases of MDI
Because the body's tissues have increased laxity, strengthening the muscles around the joint is important to improve shoulder stability. The rotator cuff muscles as well as the other muscles around the shoulder blade are important in providing dynamic stability to the joint and are the target of physical therapy. This is not a quick cure as it can take months to improve.
5. Consider Surgery Only When Other Treatments Fail
When all else fails, surgery can improve instability by physically shrinking down the joint space, which creates a tighter shoulder joint. This can be done is a number of ways, including arthroscopic and open techniques.
