what is the primary purpose of bursae?
Knee bursa. Fluid-filled, saclike cavities are known as bursae. These are located where muscles and tendons move over bony joint areas. Their function is to reduce friction caused by muscles and tendons moving against skin and bones, as well as to facilitate movement. A knee bursa, also known as a subcutaneous prepatellar bursa, aids with movement when we walk, run, stretch, or even cross our legs.