The shoulder joint is a ball and socket joint, similar to the hip. However, the socket of the shoulder joint is extremely shallow and thus inherently unstable. This means that the bones of the shoulder are not held in place adequately. Extra support is needed—that's where the labrum comes in. This cartilage is important for a properly functioning shoulder, as a torn labrum can impact movement. Luckily, most treatments aren't invasive.
To compensate for the shallow shoulder socket, the joint has a cuff of cartilage called a labrum that forms a cup for the end of the arm bone (humerus) to move within. The labrum circles the shallow shoulder socket (the glenoid) to make the socket deeper.
This cuff of cartilage makes the shoulder joint much more stable and allows for a very wide range of movements (in fact, the range of movements your shoulder can make far exceeds any other joint in the body).[1]
