Bursitis of the knee is an inflammation of one or more of the bursae in the knee. Bursae are small, fluid-filled sacs that reduce friction and cushion pressure points between bones and the tendons, muscles, and skin near joints. Knee bursitis most commonly occurs over the kneecap or on the inner side of the knee below the joint. Symptoms of knee bursitis include pain, warmth, tenderness, and swelling in the affected area. The pain can increase when moving or even at rest. Knee bursitis can be caused by overuse or strenuous activity, frequent and sustained pressure, such as from kneeling, bacterial infection of the bursa, or complications from osteoarthritis, rheumatoid arthritis, or gout in the knee. Knee bursitis can be diagnosed by a physical examination, inspection of the skin over the tender area, and imaging tests such as X-rays. Treatment for knee bursitis includes activity modification, ice, elevation, medications, therapy, and surgical or other procedures.