A bursa is a fluid-filled sac that serves to prevent friction within a joint, particularly in synovial joints which allow for significant movement and flexibility.
A pad-like sac or cavity that prevents friction within a joint is known as a bursa. Bursae are fluid-filled sacs located in regions where skin, muscle, tendons, or ligaments may rub against bone. Specifically, they are positioned to reduce friction in synovial joints like the knee, elbow, and shoulder by acting as a cushion between bones and overlying soft tissues, or between adjacent soft tissues. These structures facilitate smooth movement and prevent the direct rubbing of bones against muscles or skin.
Synovial joints, characterized by a synovial cavity filled with lubricating synovial fluid, rely on such additional structures to minimize friction and ensure efficient mobility. Bursae are found in various locations such as subcutaneous (under the skin), submuscular (between muscle and bone), and subtendinous (between tendon and bone), providing essential lubrication in various parts of the human body.