Housemaid's knee is also known as prepatellar bursitis. It is caused by inflammation of the bursa (a small fluid-filled sac) in front of the kneecap. It more commonly occurs in people who spend long periods of time kneeling. Treatment is usually supportive only and the outlook is generally very good.
Bursitis means inflammation within a bursa. A bursa is a small sac of fluid with a thin lining. There are a number of bursae in the body. Bursae are normally found around joints and in places where ligaments and tendons pass over bones. They can also be found in other places if there has been unusual pressure or friction placed on that area.
Generally, the function of a bursa is to help reduce friction and allow maximal range of motion around joints. When there is inflammation within a bursa (bursitis), the bursa swells due to an increase in the amount of fluid within the bursa sac.
There are four bursae located around the knee joint. They are all prone to inflammation, or bursitis. However, the prepatellar bursa (the bursa in between the skin and the kneecap) is most commonly affected. Its position is shown in the diagram. Housemaid's knee is the name given to inflammation of the prepatellar bursa.
There are a number of different things that can cause housemaid's knee:
For example, a fall or direct blow on to the knee.
This usually happens after spending long periods of time kneeling down, putting pressure on the patella (knee cap). Historically, this was typical of housemaids who spent long periods of time scrubbing floors on their knees; hence the term housemaid's knee.
The fluid in the prepatellar bursa sac can become infected and cause bursitis. This is particularly common in children with housemaid's knee. This usually follows a cut, scratch or injury to the skin on the surface of the knee. This injury allows bacteria (germs) to spread infection into the bursa.
If you already have an inflammatory disease such as rheumatoid arthritis, you have an increased risk of developing a bursitis. Rheumatoid arthritis is a form of arthritis that causes inflammation, pain and swelling of joints.
If you have gout, you have an increased risk of developing a bursitis. Gout is caused by a build-up of uric acid crystals. Uric acid is a chemical in the blood that is usually harmless and passed out with the urine. In gout, it builds up and collects within a joint, causing pain, inflammation and joint swelling.
Any age group can be affected by housemaid's knee. It is generally more common in males than in females. Housemaid's knee in children is more likely to be caused by infection. Infection is also a common cause of housemaid's knee in people whose immune system is not working normally. Such people include those receiving steroid treatment or those on chemotherapy treatment for cancer.
Housemaid's knee is more common in tradesmen who spend long periods of time kneeling. For example, carpet fitters, concrete finishers and roofers.
Housemaid's knee causes pain and swelling of the affected knee. You may notice redness of the skin over the knee and your kneecap may be tender. You may also have difficulty bending your knee and difficulty kneeling and walking. If housemaid's knee is caused by infection, you may have a fever (high temperature).
Your doctor is usually able to diagnose housemaid's knee simply by examining your knee. They may ask you questions about your occupation or if you have had any recent knee injury. They may also ask whether you have any history of other joint problems.
If your doctor suspects that housemaid's knee is caused by infection, they may suggest that they draw some fluid from the bursa. This is a straightforward procedure. The skin on the front of your knee is sterilised with some fluid and the procedure is carried out in a clean environment. A small needle is used to take a sample of the fluid from your prepatellar bursa, which is directly underneath the skin in front of your kneecap. This fluid is sent off to the laboratory to look for signs of infection. If infection is confirmed, the laboratory may be able to suggest which antibiotics will treat it.
You do not need any X-rays or scans to diagnose housemaid's knee.
The treatment options for housemaid's knee depend on whether or not it is caused by infection.
If your doctor suspects that your housemaid's knee is caused by infection, they may draw some fluid from your knee, as described above. They can send this fluid off to the laboratory for tests. Whilst waiting for the results, they may prescribe some antibiotics for you to take. Usually, these antibiotics can be taken by mouth. If the infection is severe, your doctor may suggest that you be admitted to hospital and given intravenous antibiotics (antibiotics into your veins).
When the doctor gets the results back from the laboratory after a couple of days, they may suggest that your antibiotics be changed. They should now know the antibiotic that is most likely to be effective in treating the infection.
If your symptoms do not seem to be improving despite 36-48 hours of antibiotics, your doctor may suggest that a small incision should be made on the front of your knee to allow the infected fluid to drain out from the bursa. This may require referral to hospital but does not normally mean an overnight stay.
Most episodes of housemaid's knee will settle with supportive treatment and do not require drugs or surgery.
Generally, the outcome is very good with appropriate treatment. You should find the condition clearing up in a few weeks.
However, if housemaid's knee is chronic (persistent) or keeps coming back you might get long-term pain and have problems moving your knee.
You should take care if you have a job or hobby that involves kneeling for a long time or frequently. In such cases, you should use thick foam cushions, or knee pads. Knee pads should especially be used by people who have already had an episode of housemaid's knee in order to prevent it from coming back.