Rotator Cuff Injury

Rotator cuff tears are tears of one, or more, of the four tendons of the rotator cuff muscles. A rotator cuff injury can include any type of irritation or damage to your rotator cuff muscles or tendons.

The rotator cuff muscles, a group of four muscles that surround the shoulder, are the: supraspinatus, infraspinatus, teres minor and subscapularis. The four rotator cuff muscle tendons combine to form a broad, conjoined tendon, called the rotator cuff tendon, and insert onto the bone of the humeral head in the shoulder. The humeral head is the ball side of the “ball and socket” shoulder joint; the socket is called the glenoid fossa. The tendons of the rotator cuff, not the muscles, are most commonly torn. Of the four tendons, the supraspinatus is most frequently torn; the tear usually occurs at its point of insertion onto the humeral head at the greater tuberosity.

Illustration of the skeletal structure of the shoulder.

Illustration of the skeletal structure of the shoulder.


Illustration of the muscles and tendons of a normal shoulder.

Illustration of the muscles and tendons of a normal shoulder.


Illustration of shoulder impingement and partial rotator cuff tears. A bone spur appears on the undersurface of the acromion.

Illustration of shoulder impingement and partial rotator cuff tears. A bone spur appears on the undersurface of the acromion.

Many rotator cuff tears cause no pain nor produce any symptoms, and are known to have an increasing incidence with increasing age. The most frequent cause of rotator cuff damage is age related degeneration and less frequently by sports injuries or trauma. Partial and full thickness tears have been found on post mortem studies and on MRI studies, in people who do not have a history of shoulder pain or symptoms.

Tears of the rotator cuff tendon are described as partial thickness tears, full thickness tears and full thickness tears with complete detachment of the tendons from bone.

  • Partial thickness tears often appear as fraying of an intact tendon.
  • Full thickness tears are through-and-through tears. These can be small pin-point tears or larger button hole tears or tears involving the majority of the tendon where the tendon still remains substantially attached to the humeral head and thus maintains function.
  • Full thickness tears may also involve complete detachment of the tendon(s) from the humeral head and may result in impaired shoulder motion and function may be significantly affected.

The most reliable symptom for determining a rotator cuff tear is probably the least common and is found when there is a complete rupture with detachment of the rotator cuff leading to the complaint of complete loss of function, such as, loss of the ability to actively move the arm away from the side of the body (loss of abduction). Fortunately, this finding is rare and when tears are symptomatic, most tears present as pain with limitation of function, a non-specific complaint that cannot distinguish between tendinitis, bursitis or arthritis. The clinical picture of a completely detached tear is more clear-cut, while the more common shoulder problems greatly overlap in their clinical presentation.

Impingement Syndrome

Primary shoulder problems may cause pain over the deltoid muscle that is made worse by abduction against resistance, called the impingement sign. Impingement reflects pain arising from the rotator cuff but cannot distinguish between inflammation, strain, or tear. Patients may report their experience with the impingement sign when they report that they are unable to reach upwards to brush their hair or to reach in front to lift a can of beans up from an overhead shelf.

The rotator cuff muscle tendons pass through a narrow space between the acromion process of the scapula and the head of the humerus. Anything which causes further narrowing of this space can result in impingement syndrome. This can be caused by bony structures such as subacromial spurs (bony projections from the acromion), osteoarthritic spurs on the acromioclavicular joint, and variations in the shape of the acromion. Thickening or calcification of the coracoacromial ligament can also cause impingement. Loss of function of the rotator cuff muscles, due to injury or loss of strength, may cause the humerus to move superiorly, resulting in impingement. Inflammation and subsequent thickening of the subacromial bursa may also cause impingement.

Symptoms Of A Rotator Cuff Injury

Patient history will often include pain or ache over the front and outer aspect of the shoulder, pain aggravated by leaning on the elbow and pushing upwards on the shoulder (such as leaning on the armrest of a reclining chair), intolerance to overhead activity, pain at night when lying directly on the affected shoulder, pain when reaching forward (e.g. unable to lift a gallon of milk from the refrigerator). Weakness may be reported, but is often masked by pain and is usually found only through examination. With longer standing pain, the shoulder is favored and gradually loss of motion and weakness may develop which, due to pain and guarding are often missed by the patient and are only brought out during the examination.

Service Providers

Henry Small, M.D.

Dr. Small is a board certified orthopedic surgeon. He has 23 years of experience.