Bursitis is the inflammation of one or more bursae in the body. Bursae are small sacs filled with lubricating synovial fluid that decrease friction at contact points between bones, skin, tendons, and muscle. Irritation of the bursae usually occurs as a result of overuse or trauma, but may also occur due to systemic illnesses. While there are more than 150 bursae in the human body, common sites of bursitis include the shoulder, elbow, hip, and knee. Bursitis is typically associated with redness and swelling, but may also be associated with pain, warmth, or decreased range of motion. Bursitis is typically treated with conservative management, but additional evaluation and treatment may be required if initial management fails.