Bursae in the ankle

A "bursa" is a small fluid-filled sac that sits near a bone. It cushions and protects nearby tissues when they rub on or slide over bones. These sacs, called "bursae," are found in many places throughout the body. Bursitis happens when a bursa gets irritated and swollen.

The bursa in the ankle most likely to get bursitis is called the "retrocalcaneal bursa." The "subcutaneous calcaneal bursa" can also be affected by bursitis.