Bursa is a fluid-filled sac between layers of MUSCLEthat buffers the movement of muscles against each other. A synovial membrane, which secretes a lubricating fluid (synovial fluid), lines the inside of the bursa. This is the same kind of membrane and fluid that encloses and lubricates the joints. Most people have between 130 and 160 bursae throughout their bodies, typically located near joints. Bursae are vulnerable to INFLAMMATION (BURSITIS) and fibrosis (scarring), both of which cause pain and interfere with the bursa’s proper function.
For further discussion of bursae within the context of musculoskeletal structure and function, please see the overview section “The Musculoskeletal System.”