Bursa

Bursa, a sac containing fluid interspersed between a tendon and the surface over which it glides; or lying beneath the skin covering some long prominence. Bursae of the former class are called synovial bursae, and when situated in the neighbourhood of a joint they frequently communicate with the joint cavity. The other variety of bursa is the bursa mucosa, an example of which is the bursa patellae, or the bursa situated over the olecranon process of the elbow. Bursae are liable to enlargement under the influence of pressure. A familiar example of such a condition is the enlarged bursa patellae produced by kneeling, and causing the condition known as housemaid's knee, a trouble of an allied nature sometimes developed in miners - the miner's elbow - being due to enlargement of the bursa over the olecranon process. Suppuration may occur in the sac of an enlarged bursa producing a bursal abscess.