Bursa is the Greek word for 'a wine skin'. When a bursa becomes inflamed it's known as bursitis. Prepatellar bursitis is commonly called 'housemaid's knee'. The bursa becomes tender and swollen, and movement of the joint may become restricted. If the bursa becomes infected it may become red, hot, and painful.
Prepatellar bursitis is usually caused by repeated friction between the skin and the patella. It can also be caused by injury, infection, or underlying inflammatory condition. However, often the cause is unknown.
The condition occurs in situations where someone is repeatedly on their knees. It used to be characteristic of housemaids who spent a lot of their working day on their knees cleaning - hence the name. Now it's more common among those who have to spend time on their kneees at work, such as carpet fitters.
People can reduce their risk of bursitis by avoiding repeated friction between the skin and the patella, for example by avoiding kneeling.
Treatment usually involves rest, cold and heat therapy, and non-steroidal anti-inflammatory drugs. Fluid may need to be aspirated from the bursa, and hydrocortisone may be injected. If the condition persists then surgical excision may be recommended