What Causes Laxity in a Shoulder Injury?
Laxity of the shoulder refers to looseness of soft tissue that surrounds the shoulder joint. A shoulder is generally referred to as lax when the range of its external rotation with the arm on the side exceeds 80 degrees. Laxity may affect the shoulder's ligaments, tendons, muscle and capsule. The shoulder capsule refers to the area of ligament tissue that surrounds the shoulder like an envelope. Shoulder laxity is usually painless, and is commonly associated with athletes such as swimmers and baseball pitchers who typically cock their arms way back while engaging in sports activities.
-
Causes of Shoulder Laxity
-
Shoulder laxity can occur naturally. In this case, a person's collagen, the protein structures that make up soft tissues, is naturally flexible. This means there would be fewer links holding fibers together, therefore resulting in more laxity. Overuse of the shoulder, especially in the case of athletes, can also result in laxity. Athletes who engage in sports activities with a lot of repetitive, overhead shoulder motions generally develop more laxity in their shoulders. Repetitive overhead movements cause the ligaments and capsule surrounding shoulder joints to become loose. Some athletes are naturally predisposed to generalized ligamentous laxity, which means their bodies' joints are generally looser than the average person's.
Laxity vs. Instability
-
It is important to make a distinction between shoulder laxity and instability, as the two terms can easily be interchanged. As opposed to laxity, shoulder instability is a condition characterized by painful increased range of motion. Instability can cause the shoulder to slip in its socket, a condition known as subluxation, or a complete dislocation of the shoulder joint, which would require emergency relocation maneuvers. Instability can occur as a result of a single traumatic event or from repetitive stress due to overuse. Athletes with ligamentous laxity are prone to having multidirectional subluxation.
-
Risk Factors
-
Excessive shoulder laxity puts individuals at an increased risk of shoulder instability and dislocation. Individuals with lax shoulders are therefore encouraged to often participate in joint strengthening exercises, especially if they are athletic. Individuals with too much shoulder give should also seek advice before participating in sports activities that would require repetitive overhead motions.
Generalized Laxity Test
-
A simple test can be performed in order to determine whether or not you have generalized ligamentous laxity. The test involves sticking out one of the thumbs and then bending the wrist downward. Using the opposite hand, try to reach the stuck-out thumb to the forearm. If the thumb comes close to or reaches the forearm, you have generalized ligamentous laxity.
Tips and Warnings
-
The normal shoulder range of laxity varies from person to person. One person's shoulder may be more lax than another's. A physician must therefore make the distinction between shoulder laxity and instability.
Unlike laxity, instability is usually painful and the extra motion presents a problem.
-
References
Resources
- Photo Credit Image by Flickr.com, courtesy of Josh Pesavento
