The labrum is the articular surface (the area where the ball of the arm bone or humerus connects to the actual joint surface or glenoid cavity *the socket of the shoulder). Its like looking at the Universal Joint on a car crankshaft. The surface on the inside of the socket is where the labrum forms a secure ‘cuff’ for the bony humerus to insert into. Like a ring of fibre that makes the articulation more secure, it helps to create a deeper rim. Like the rubber ring on a preserving jar.
The chewing action of jaw is often taken for granted, but this highly specialised joint is something that can have far reaching implications to sufferers. TMD (Temporomandibular Joint Disorders) or TMJ (Temporomandibular Joint) issues are often cited by medical professionals as a cause of all manner of symptoms and ailments. Like 'sciatica' many 'Dr Googles' lead people to believe that they have this condition that becomes a generic term describing any pain that may sometimes be inexplicable or undefinable.