Prepatellar bursitis / Housemaids knee
Commonly known as housemaid’s knee, prepatellar bursitis refers to a painful swelling over the kneecap (patella). Bursitis means inflammation (-itis) of the bursa, a small fluid-filled sac that acts as a soft cushion preventing friction between bones and the surrounding soft tissues in a joint.
The knee joint is protected on the front and sides by more than a dozen bursae. The prepatellar bursa is the one in front, located between the knee cap (patella) and the overlying skin. Its role is to reduce friction between the bone and the skin when the knee is flexed. Inflammation leads to swelling and pain at the front of the knee. The overlying skin becomes tender and bending the knee causes pain.
Factors leading to prepatellar bursitis:
Inflammation of the prepatellar bursa may be acute (sudden onset) or chronic (developing over time).
Acute inflammation usually results from a direct trauma such as falling on the knees. This ruptures the minute blood vessels in the lining of the sac, which may cause bleeding and swelling. Inflammation starts to repair the damage.
Acute infection, as a result of contamination of the bursa from an open skin wound may also stimulate an inflammatory response.
Chronic bursitis develops gradually as a result of repeated minor trauma. Kneeling on hard surfaces for prolonged periods as while scrubbing or polishing floors (hence the name “housemaid’s knee”), puts extra stress on the bursa and leads to inflammation.
Other joint diseases may also lead to inflammation of the prepatellar and other knee bursae, such as:
Gout in which there is deposition of uric acid crystals in the joint space which irritate the surrounding tissue leading to localised inflammation.
Rheumatoid arthritis, a generalised inflammatory disorder involving several body organs, but which mainly affects the joints.
All the classic signs of inflammation are present. These include:
- Pain and tenderness on the front of the knee above and just below the kneecap.
- Swelling of the area may be gross in severe cases.
- The temperature of the overlying skin is raised and the skin appears red
- Movement is difficult; bending the knee irritates the bursa leading to pain
- In the case of infection an abscess may form over the kneecap.
- Fever, in case of severe infection
- In the case of chronic prepatellar bursitis a tender mobile lump may be palpated over the kneecap.
Diagnosis is mostly clinical, based on the tell-tale symptoms and appearance. To rule out infection, a small amount of fluid is aspirated from inside the inflamed bursa and is tested in the laboratory.
For prepatellar bursitis caused by acute trauma the first line of therapy includes painkillers and the RICE regime to control symptoms. This includes providing rest to the irritated site, ice application and mild compression over the knee cap, and elevating the affected leg. This protocol helps prevent pain and swelling.
Any skin wound also needs to be addressed. Antibiotics are prescribed if lab tests are positive for infection. Penicillin is the antibiotic of choice for the treatment of knee bursitis. Treatment should not be delayed as the infection may spread to involve adjacent joint structures, especially in immunocompromised individuals.
If the swelling does not subside after initial supportive therapy, fluid may need to be drained – a small needle is used to aspirate the fluid from the inflamed bursa. The fluid may need to be drained multiple times.
Steroids have a strong anti-inflammatory action and steroid injections at the site drastically reduce symptoms over a short period of time, however their use is not without significant complications. Moreover, as steroids weaken the body’s defense mechanism; these should only be prescribed once infection has been ruled out and then only in refractory cases.
For chronic cases, the underlying cause of the damage to the bursa should be discovered and corrected. For those who work in a kneeling position, knee supports or braces are advised.
A knee support is a protective padding that covers the front of the knee, providing additional cushioning to the kneecap. It thus prevents further agitation of the already inflamed prepatellar bursa.
In persistent or recurrent bursitis, surgery may be necessary. The inflamed bursa is removed permanently. This does not affect the functioning of the knee and carries no risk of any disability.
Avoiding local trauma is imperative for proper treatment and future prevention.