What is the rotator cuff?

The rotator cuff is a group of four muscle/tendon units which are responsible for certain motions of the shoulder joint. Actually, the shoulder consists of at least four different joints but the primary joint in question is the glenohumeral joint, the joint comprised of the head of the humerus (the “arm-bone”) and the glenoid fossa (the outer rim of the scapula or shoulder blade).

What is the purpose of the rotator cuff?

The rotator cuff tendons are responsible for motion, strength and control of activities involving the arm. For example, tasks involving lifting, rotation, pulling, and pushing, all require the rotator cuff muscles. In addition, sports activities such as throwing, swimming, weight lifting, and racquet sports, all involve usage of the rotator cuff muscles.

Who gets a rotator cuff problem?

Virtually everybody by middle age has some damage to their rotator cuff, if one were to examine the rotator cuff under a microscope. The reason for this is the unique anatomy of the rotator cuff. First, there is a region of limited blood supply within the tendons; this limited circulation predisposes the tissues to injury and makes the healing process more tenuous. Second, the shoulder joint has the greatest flexibility (total range of motion) of any joint in the body, thus allowing a remarkable number of movement patterns for the arm. This increased flexibility also predisposes to increased risk of injury. Third, the acromion process of the scapula (shoulder blade) over-hangs the glenohumeral joint; the rotator cuff tendons course from the upper back (the scapular region), under the acromion, to attach to the upper arm and therby control upward and outward motion of the arm (elevation and abduction). Therefore, as the arm moves upward and outward, these tendons can become trapped between the head of the humerus and the acromion process. This process is known as impingement. In summary, the tenuous circulation, unique flexibility, and potential for impingement of the rotator cuff tendons result in almost univeral microscopic injury by middle age.

What is the consequence of impingement?

Normally, there is fraying of individual fibers of the rotator cuff tendons, most commonly the supraspinatus tendon which is responsible for elevation and outward motion (abduction). When individual fibers tear, there may be microscopic bleeding into the injured tissue. This results in inflammation, edema 9swelling), and pain. As the tissues attempt to heal, there may be fibrosis (scar tissue) with consequent decreased flexibility or decreased strength. Sometimes in the healing process, calcium deposits may accumulate due to the healing process. If the process is allowed to repeat itself, ultimately there may be a gross tear of the rotator cuff tendon.

What is the clinical presentation of the patient with impingement?

Patients may complain of a variety of problems related to rotator cuff injury. These include tendonitis (the impingement syndrome), calcific tendonitis, bursitis, rotator cuff tear, or adheasive capsulitis (frozen shoulder). These will now be discussed in greater detail.