Rotator Cuff Anatomy

“In My Office”

‘I was lifting a box overhead and felt a painful pop in my shoulder – what is the rotator cuff?’

The shoulder is a ball (humeral head) and socket (glenoid) joint, which permits a great deal of motion and flexibility. Four separate muscles attach to the wingbone (scapula) and as they travel out to the side, each attaches to an individual tendon. The tendons blend together to form a sheet that covers or “cuffs” the ball of the shoulder.  When the muscles are activated, they help to stabilize or rotate the shoulder. Thus, the sheet of tendon tissue is called the “rotator cuff”. A bony roof of the shoulder (acromion) covers over a portion of the rotator cuff and can both protect or injure the rotator cuff. A bursa or thin tissue sack rests between the cuff and the roof of the shoulder. A small amount of fluid is present in the sack and allows the walls to slide easily past each other. In the healthy shoulder, this protective structure helps the rotator cuff glide beneath the bony roof without incurring damage or wear. One of the two biceps tendon attachments around the shoulder is a rope-like structure that travels from the arm up into the shoulder between the front and top tendons of the rotator cuff. Biceps tendon degeneration often accompanies rotator cuff disorders.

The rotator cuff is a component of your shoulder that is often injured during heavy lifting or repetitive overhead use. The tissue may become inflamed and result in ‘rotator cuff tendonitis”. Similarly, inflammation of the bursa is termed, ‘bursitis’. While the rotator cuff is a robust and stout structure when we are young, with age and use it can become worn and frayed resulting in a partial-thickness tear. Eventually the tendon separates completely from the arm bone and a full thickness defect in the tendon is present. Those complete thickness tears tend to progress and become larger with time. You may experience deep aching and / or night pain although symptoms are quite variable. As tears become larger, atrophy or shrinkage of the muscles along with shoulder weakness may worsen over time. When you are early in the development of rotator cuff problems, more management options are available and treatment results tend to be better. So, its worthwhile having your shoulder evaluated if pain persists more than a few weeks.