Bursitis
Bursitis refers to the inflammation of a bursa, esp. between bony prominences and muscle or tendon, as in the shoulder and knee. Common forms include rotator cuff, miner’s or tennis elbow, housemaid’s knee, and bunion.
Bursa is a padlike sac or cavity found in connective tissue usually in the vicinity of joints. It is lined with synovial membrane and contains a fluid (synovia) that reduces friction between tendon and bone, tendon and ligament, or between other structures where friction is likely to occur.