The shoulder is a ball and socket joint. The top of the humerus (arm bone) forms the ball, which fits, into the socket of the scapula (shoulder blade). The joint is held together with fibrous tissue that surrounds the socket. This is called the labrum. Its function is to deepen the socket and provide a type of bumper to help prevent the humeral head from sliding out of its socket.
Diagnosis:
Posterior labral injuries are thought to occur in contact athletes. The mechanism of injury is the result of a posteriorly directed force on the shoulder. This can occur with blocking in football. The repeated episodes of excessive shear forces directed against the posterior labrum causes the ultimate failure of the labrum. It has also been proposed that repetitive microtrauma eventually leads to posterior labral failure. A detailed physical examination by a Rothman sports medicine physician can evaluate the shoulder and determine if the labrum is involved in the patients complaints. The patient complains of pain with aggressive shoulder activity. During the physical examination, provocative posterior shifting of the humeral head can duplicate the pain. Plain x-rays would demonstrate any boney injury including fractures of the shoulder. The definitive diagnosis is made with an MRI arthrogram scan.