Calcific bursitis refers to calcium deposits within the bursae. This most occurs in the shoulder area. The most common bursa for calcific bursitis to occur is the subacromial bursa. A bursa is a small, fluid-filled sac that reduces friction, and facilitates movements between its adjacent tissues (i.e., between tendon and bone, two muscles or skin and bone). Inflammation of the bursae is called bursitis.