What is the clinical anatomy of bursae relative to bursitis?

Updated: Dec 11, 2020
  • Author: Kristine M Lohr, MD, MS; Chief Editor: Herbert S Diamond, MD  more...
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Answer

Bursae are flattened sacs that serve as protective buffers between bones and overlapping muscles (deep bursae) or between bones and tendons or skin (superficial bursae). These synovial-lined sacs are filled with minimal amounts of fluid to facilitate movement during muscle contraction. Deep bursae (eg, subacromial and iliopsoas bursae) are located in the fascia. Superficial bursae (eg, olecranon and prepatellar bursae) are located in the subcutaneous tissue.

There are two types of bursae: constant and adventitial. Both types can be involved in acute or chronic bursitis. Constant bursae have the following characteristics:

  • They form during embryologic development
  • They are lined with endothelial cells
  • They are located between bones and tendons or skin
  • They contain synovial cells that secrete a lubricating fluid rich in collagen and proteoglycans

Adventitial bursae (examples include those that develop over a bunion and osteochondroma) have the following characteristics:

  • They form later in life in response to repeated trauma or constant friction and pressure
  • They lack endothelial cells
  • They do not contain synovial fluid

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