The labrum is a lip of cartilage that goes around the rim of the glenoid, or saucer portion of the ball-and-saucer shoulder joint. The presence of the labrum helps to deepen the saucer and therefore provide some stability to the joint. Also, this is the structure through which ligaments that connect the ball and saucer to each other pass. Consequently, when there is a tear in the labrum, the shoulder joint can become unstable. Also, the labral tear can itself be painful.
Labral tears can be difficult to diagnose, even with the latest imaging techniques such as MRI. Sometimes they can only be suspected and not reliably diagnosed until actual inspection of the joint through arthroscopic surgery. Fortunately, most labral tears are amenable to being addressed through arthroscopic surgical techniques, in the hands of those surgeons skilled in arthroscopic surgery.