Bursas are thin, slippery sacs located throughout the body that act as cushions between bones and soft tissues. They contain a small amount of lubricating fluid that allows the skin to move freely over the underlying bone. The olecranon bursa lies between the loose skin and the pointy bone at the back of the elbow called the olecranon. Normally, the olecranon bursa is flat. If it becomes irritated or inflamed, more fluid will accumulate in the bursa and bursitis will develop.