Bursitis Causes

The most common causes of bursitis are trauma, infection, and crystal deposits.

Trauma

Trauma causes inflammatory bursitis from repetitive injury, which results in widening of the blood vessels. This allows proteins and extracellular fluid into the bursae and the bursae react against these "foreign" substances by becoming swollen.

• Chronic: The most common cause of chronic bursitis is minor trauma that may occur to the shoulder (subdeltoid) bursa from repetitive motion, for example, throwing a baseball. Another example is prepatellar bursitis (in front of the knee) from prolonged or repetitive kneeling on a hard surface to scrub a floor or lay carpet.
  
  
• Acute: A direct blow (let's say you accidentally bang your knee into a table) can cause blood to leak into the bursa. This rapid collection usually causes marked pain and swelling, most often in the knee.

Infections

Bursae close to the surface of the skin are the most likely to get infected with common organisms; this is called septic bursitis. These bursitis-causing bacteria are normally found on the skin: Staphylococcus aureus or Staphylococcus epidermis. People with diabetes or alcoholism and those undergoing steroid treatments or with certain kidney conditions, or who may have experienced trauma may be higher risks for this type of bursitis. About 85% of septic bursitis occurs in men.

Crystal deposits

People with certain diseases such as gout, rheumatoid arthritis, or scleroderma, for example, may develop bursitis from crystal deposits. Little is known about how this process happens. Uric acid is a normal byproduct of daily metabolism. People who have gout are unable to properly break down the uric acid, which crystalizes and deposits in joints-a mechanism for causing bursitis.