What is Instability?
The shoulder joint, one of the most mobile joints in the body, is also one of the most unstable. Instability is when the bones in one of the shoulder joints move out of their normal position. This may result in dislocation or subluxation and cause pain and unsteadiness when raising the arm or moving it away from the body. Subluxation is when the joint partially dislocates.
The ball slides partly out of the socket but does not actually dislocate completely. Dislocation occurs when the ball is completely displaced out of the socket. A sensation of this is when lifting the arm overhead the shoulder may feel like it is slipping out of place. Sometimes the feeling may just be uncomfortable, as if the arm is “dead” or numb. Patients are often “apprehensive” with certain motions.
Types of Instability
By far, the most common type of instability is anterior, when the shoulder comes out the front. Multidirectional instability refers to the joint being unstable in more than one direction. A typical multidirectional instability involves anterior (front) instability and inferior (down) instability. However, a posterior (back) direction could also be involved, but is rare and usually only seen with an unusual trauma or seizure disorders. Multidirectional instability can be seen in swimmers or other athletes who repetitively use their upper arm and shoulder.
Depending on the severity of the injury and the patient’s age, treatment options vary. In younger patients the shoulder is more likely to repeatedly dislocate which can significantly limit a person’s activities and lead to possible joint degeneration. For recurrent dislocations, surgery may be recommended to repair torn ligaments and capsule. There are arthroscopic and open surgical techniques available for shoulder stabilization.