What's Housemaid's Knee?

Arthritis treatment doesn't strictly always involve joint disease.

Bursitis is one of the most common soft tissue disorders seen by a rheumatologist. The term "bursitis" describes inflammation of a bursa. A bursa (plural is "bursae") is a small fluid-filled sack that cushions a joint or areas near joints.

The most common cause of bursitis is probably trauma. Repetitive motion and infection can also cause it.

One of the more common types of bursitis is termed "housemaid's knee." This is a form of bursitis that affects the prepatellar bursa. The prepatellar bursa lies in front of the patella (kneecap) and the patellar tendon. It is called "housemaid's knee" because the most common cause is trauma due to kneeling.

Another bursa, the infrapatellar bursa lies just below the prepatellar bursa and it also may be affected at the same time.

Bursitis in this area can be seen in plumbers, carpet layers, electricians, and other people for whom long-term kneeling is an important part of the work process.

What is seen on examination is swelling in front of the kneecap. There may also be redness and heat. Tenderness occurs if pressure is applied. Also, bending the knee increases the pain felt in front of the kneecap.

The diagnosis is apparent by history and physical examination. Diagnostic ultrasound can help confirm the presence of fluid within the bursa. X-rays are generally not useful and may show soft tissue swelling only.

Magnetic resonance imaging is rarely needed... but it may disclose the diagnosis in difficult cases.

The major concern when a patient with prepatellar bursitis presents, is infection. This is called "septic bursitis" and is considered a medical emergency. Heat, swelling, redness, and pain are almost always present in the presence of infection.

Fever and chills may also occur. The history usually uncovers a history of trauma involving the knee perhaps with an associated puncture wound or scrape. Tenderness is exquisite.

The diagnosis is established by aspirating fluid from the bursa (best done using ultrasound guidance).

Once aspirated, the fluid should be sent for culture. Steroids should not be injected! If infection is present, then the appropriate antibiotic should be started. While oral antibiotics are usually sufficient, intravenous antibiotics may be required if the infection is serious or has progressed.

It may be necessary to repeat the aspiration of the bursa multiple times to ensure sterilization of the bursal fluid has occurred. Prevention of recurrence is importance. Kneepads are extremely useful for this task.