WHAT CAUSES SHOULDER INSTABLITY?
With significant trauma to a previously normal joint, the humeral head can be forcefully subluxed or dislocated. The capsule, ligaments, or labrum can be stretched, torn, or detached from the bone. When the humeral head is back in place (reduced) [Figure 4] these structures can heal in a loose or stretched position which may increase the risk of future episodes of subluxation or dislocation. [Figure 4] With each additional episode, further tissue damage can occur increasing the tendency towards future instability. Alternatively, some people are born with somewhat loose shoulder ligaments (the have a loose or spacious capsule). Instability can occur without any trauma or following relatively minor injury.
