Rotator cuff disorders are caused by a combination of factors. The
rotator cuff moves within a confined space called the subacromial space. Also
within that space is a small sac of fluid (subacromial
bursa), which serves as a cushion between the
tendons and bone. When the subacromial space becomes
smaller due to inflammation, bone spurs, or fluid buildup, the rotator cuff
tendons may be squeezed and rub against bone (impingement). As a
result, the tendons may become damaged and irritated, causing bleeding and
inflammation of the bursa or tendons. With continuing
damage, the tendons become stringy (fibrous), weaker, and less flexible. Eventually, this may lead to partial or even
A rotator cuff is more easily damaged or torn as
age-related degeneration develops (tendinosis). The factors below often occur together or
Bones that are irregularly shaped can affect
how the rotator cuff moves in the subacromial space. You may be born with these
irregularities, or they may occur after some type of injury, such as a broken
bone. If the acromion is hooked or curved,
impingement or degeneration of rotator cuff tendons may be more
As you age, everyday activities and normal wear and tear
lead to some changes in the rotator cuff, such as:
General degeneration of the tendon, which
includes thinning, fraying, and tearing.
Joint looseness and muscle imbalance in the
shoulder can cause damage to the tissue.
Repetitive activities, especially forceful
overhead motions, can damage the rotator cuff. These motions are common in
certain sports or occupations, including throwing a baseball, the overhead
swing in tennis, swimming, lifting, or painting.
Repetitive activity can cause tendons to
rub or scrape against the acromion, which can irritate the rotator
Repeated overhead motions can damage stabilizing ligaments
and result in an imbalance of opposing shoulder muscles, which may cause
tendons to rub against the bones (impingement).
Overuse may occur with or be closely related to
repetitive activities. Normal motions made frequently over a long period can
stress or injure rotator cuff tissues. Athletes, including young people, may
develop tendinitis from overuse in throwing, swimming, and racquet sports.
Overuse can cause the shoulder joint to
become unstable and allow the ball of your upper arm bone (humeral head) to
move upward, narrowing the subacromial space where the rotator cuff moves. In
this narrowed space, the rotator cuff is squeezed, forcing the tendon to rub
against bone (impingement).