Prepatellar bursitis, also known as housemai's knee, is a common cause of swelling and pain above the patella (kneecap), and is due to inflammation of the prepatellar bursa. This structure is a superficial bursa with a thin synovial lining located between the skin and the patella. The bursa develops within the first years of life as a result of mechanical pressure and friction, and it serves the purpose of reducing friction on underlying structures and allowing maximal range of motion in the knee. Aseptic prepatellar bursitis is commonly caused by repetitive work in a kneeling position, hence the name "housemaid's knee".