Doctor's Notes on Rotator Cuff Injury
The rotator cuff is a group of four tendons that stabilize the shoulder joint. The tendons connect to the four muscles that move the shoulder in various directions: the subscapularis muscle, the supraspinatus muscle, the infraspinatus muscle, and the teres minor muscle. An injury to the rotator cuff is a very common cause of shoulder pain and can be caused by an acute injury or from repetitive strain. There may be partial or complete tearing of the tendons.
Symptoms and signs of rotator cuff injury include pain in the shoulder and upper arm that can be severe. The pain may be felt at night or when moving the arm in certain ways. If the injury is due to repeated small traumas over time, the pain may start as mild and may worsen over time. If the injury is sudden (acute) the pain may come on suddenly and be intense. Associated symptoms can include a cracking sound when moving the shoulder.
Rotator Cuff Injury Symptoms
Symptoms of a rotator cuff injury are due to the inflammation that accompanies the strain. This inflammation causes swelling, leading to the clinical picture of pain and decreased range of motion. Because the muscles and tendons of the rotator cuff are hidden well below skin level, it may be hard to feel the swelling that accompanies the injury, but that swelling within the small space that makes up the shoulder joint prevents the normal range of motion of the shoulder and causes the pain that occurs with movement.
- Acute rotator cuff tear
- Symptoms can be a sudden tearing sensation followed by severe pain shooting from the upper shoulder area (both in front and in back) down the arm toward the elbow. There is decreased range of motion of the shoulder because of pain and muscle spasm.
- Acute pain from bleeding and muscle spasm: This may resolve in a few days.
- Large tears may cause the inability abduct the arm (raise it away from the side of the body) due to significant pain and loss of muscle power.
- Chronic rotator cuff tear
- Pain usually is worse at night and may interfere with sleep.
- Gradual weakness and decreased shoulder motion develop as the pain worsens.
- Decrease in the ability to abduct the arm (move it out to the side). This allows the arm to be used for most activities but the affected person is unable to use the injured arm for activities that entail lifting the arm as high as or higher than the shoulder level to the front or side.
- Rotator cuff tendinitis
- More common in women 35-50 years of age
- Deep ache in the shoulder also felt on the outside upper arm over the deltoid muscle
- Point tenderness may be appreciated over the area that is injured
- Pain comes on gradually and becomes worse with lifting the arm to the side (abduction) or turning it inward (internal rotation)
- May lead to a chronic tear: When a rotator cuff tendon becomes inflamed (tend=tendon +itis=inflammation), it runs the risk of losing its blood supply, causing some tendon fibers to die. This increases the risk that the rotator cuff tendon can fray and partially or completely tear.
Rotator Cuff Injury Causes
Injuries to muscle-tendon units are called strains and are classified by the amount of damage to the muscle or tendon fibers. Grade I strains involve stretching of the fibers without any tears. Grade II injuries involve partial muscle or tendon tearing, and grade III injuries are defined as a complete tear of a muscle or tendon.
The muscles and tendons in the rotator cuff group may be damaged in a variety of ways. Damage can occur from an acute injury (for example from a fall or accident), from chronic overuse (like throwing a ball or lifting), or from gradual degeneration of the muscle and tendon that can occur with aging.
- Acute rotator cuff tear
- This injury can develop from sudden powerful raising of the arm against resistance or in an attempt to cushion a fall (for example, heavy lifting or a fall on the shoulder).
- A rotator cuff tear requires a significant amount of force if the person is younger than 30 years of age.
- Chronic tear
- Chronic rotator cuff tears are typically found among people in occupations or sports requiring excessive overhead activity (examples, painters, baseball pitchers, tennis players)
- The chronic injuries may be a result of a previous acute injury that has caused a structural problem within the shoulder and affected the rotator cuff anatomy or function (for example, bone spurs that impinge upon a muscle or tendon, causing inflammation).
- Repetitive trauma to the muscle by everyday movement of the shoulder
- A chronic tear may lead to degenerative changes to the tendon, leading to worsening pain, decreased range of motion, and decreased function.
- Degeneration (wearing out) of the muscles and tendons with age
- This usually occurs where the tendon attaches to bone. The area has poor blood supply and a mild injury may take a long time to heal and potentially lead to a secondary tear of the cuff.
- Calcific tendinitis describes a condition characterized by calcium deposits that develop within the tendon itself where it has sustained chronic inflammation.
- Glenohumeral subluxation
- If the shoulder joint is unstable and loose, the rotator cuff needs to work harder to make certain the joint does not partially dislocate (subluxate) with movements.
- Repetitive stress of these muscles can lead to rotator cuff muscle weakness, discomfort, and chronic injury.
Rotator cuff tears can be career-ending for professional athletes and are one of the most common causes of shoulder pain for everyday folks. So, what is a rotator cuff and how can it tear?
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Kasper, D.L., et al., eds. Harrison's Principles of Internal Medicine, 19th Ed. United States: McGraw-Hill Education, 2015.