Overview of Glenohumeral Instability

Description: Overview of Glenohumeral Instability, Michael L. Pearl, MD. Web Archive copy Last posted 2006
The shoulder faces unique challenges in comparison to other joints when it comes to stability. The arm moves through an extremely wide ROM, and often does so while under very heavy mechanical loads. To understand the mechanisms of glenohumeral stability, it is instructive to compare this joint with the hip and knee. The hip, with its ball and socket configuration, has intrinsic mechanical stability and a truncated spherical ROM. In contrast, the knee has minimal intrinsic bony stability and must rely on a complex array of ligaments for its stability, an arrangement that allows for essentially 2 degrees of freedom. The shoulder borrows from both of these mechanisms with modifications that provide less stability and greater ROM.