Pathophysiology: Rotator Cuff Tendinopathy

Physiology
- Rotator cuff is a group of 4 tendons (SITS) that stabilizes the shoulder joint.
- Allows movement: raise and rotate arms.
- When you raise your arm above your head:
o The supraspinatus tendon (upper) and the subacromial bursa will glide on the acromion of scapula.
o The undersurface of acromion may be rough/abnormally shaped. It rubs or scrapes the bursa and tendon.
- Repetitive activities (with overhead motion) can result in
o Bursitis  inflammation of bursa
o Tendinitis  inflammation of tendon

Pathology

Tendinopathy = Tendinitis (inflammation) @ tendinosis (tear)
- Normally, the rotator cuff moves within a confined space (subacromial space) with subacromial bursa (cushion between tendons and bone).
- When the subacromial space becomes smaller due to inflammation, bone spurs or fluid build-up, 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.

- Over time, tendon may wear against the undersurface of acromion, causing TEAR & bleeding.
- Tears heal  replacement by scar tissue (weak/thickened/less flexible/fibrous)
- Gradual scarring of tendon  the entire rotator cuff weakens
- Finally, rotator cuff cannot balance the upward pull of the deltoid muscle
o This may further damage the tendon, renewing the cycle of tearing and scar formation
o The weaker the tendon becomes, the more susceptible it is to partial or complete tears

- Cycle of inflammation  tearing of tendons  scar formation
- This results in pain and loss of function
- May lead to other shoulder problems (e.g. frozen shoulder syndrome)
o Adhesive capsulitis  frozen shoulder
o Stiffness, pain, limited range of movement
o Tissues around the joint stiffen, scar tissue forms

- Rotator cuff tears occur when the tendons become weak from inflammation/scarring/fraying
- Tears result from slow, progressive damage over time.

A rotator cuff is more easily damaged or torn as age-related degeneration develops.

The factors below often occur together or overlap:
a. Bones are that irregularly shaped  affect cuff movement in subacromial space
b. Normal wear and tear lead to changes in rotator cuff, such as:
a. General degeneration of the tendon  thinning, fraying and tearing
b. Decreased blood supply to tendons
c. Arthritis of the acromioclavicular (AC) joint  results in bony growths that can damage rotator cuff
c. Joint looseness and muscle imbalance in the shoulder
a. Formation of scar tissue
b. Changes in the tissue itself
d. Repetitive activities, especially forceful overhead motions
a. Repetitive activity – tendons rub or scrape against the acromion (this can irritate the rotator cuff)
b. Repeated overhead motions – damage stabilizing ligaments and result in an imbalance of opposing shoulder muscles (cause tendons to rub against the bones – impingement)
e. Overuse
a. Young athletes – tendinitis (throwing/swimming/racquet sports)
b. Lead to functional overload (shoulder joint becomes unstable)
c. The ball of humerus (humeral head) moves upward, narrowing the subacromial space where rotator cuff moves.
d. In this narrowed space, the rotator cuff is squeezed, forcing the tendon to rub against bone (impingement).