What is a bursa?

A small structure that helps tissues glide

A bursa is a thin sac lined by a synovial membrane and containing synovial fluid. Its position allows it to reduce friction where neighbouring tissues move against one another. The singular term is bursa; the plural is bursae.

Depending on its location, a bursa may lie between a tendon and bone, between muscle and bone, or between skin and a bony prominence. It is useful to think about the structures on either side of it, rather than considering the bursa in isolation.

Where are bursae found?

Bursae occur in many regions, including the shoulder, elbow, hip and knee. Around the shoulder, a bursa helps reduce friction between neighbouring structures during movement. At the back of the elbow, the olecranon bursa helps cushion the skin over the bony prominence.

These examples show why location matters. A bursa beneath a tendon has a different relationship to movement and loading from one close to the skin and exposed to direct pressure.

What is the difference between a bursa and bursitis?

A bursa is an anatomical structure. Bursitis describes inflammation of a bursa. The terms are related, but they do not mean the same thing: having a bursa is normal, and mentioning one does not imply that it is painful or inflamed.

When a bursa becomes irritated or inflamed, symptoms can include pain, swelling, tenderness and restricted movement. These symptoms need to be considered in the context of the wider presentation.