Bursitis is swelling or inflammation of a bursa. A bursa is a sac of fluid that cushions bones, tendons and muscles from each other. Your body has about 160 bursae, of which 11 are in the knee. Knee bursitis is inflammation of one or more of these 11 bursae.

Knee bursitis affects the bursa over the kneecap; this is medically termed prepatellar bursitis, colloquially termed housemaid’s knee. Knee bursitis also commonly affects the inner side of the knee.

How serious is bursitis?

Bursitis can affect any of your bursae, mostly those in the buttocks, elbow, foot, knee, hip, thigh, or shoulder, and is not normally serious. It causes only mild pain and discomfort, and, with suitable treatment, usually goes away within a month or less. Knee bursitis is no exception so if you have knee bursitis, there’s no need to worry too much.

Any bursitis may, however, reflect a more serious underlying problem. Consequently, if you suffer from knee bursitis, you should see your GP so that he or she can examine you and send you to an orthopaedic specialist if necessary.

What causes knee bursitis?

The causes of knee bursitis are the same as those of any bursitis:

  • Sustained pressure to the joint: this will usually be frequent. The kneeling practised by housemaids in the past gives the condition its common name.
  • Frequent trauma to the joint: sports that involve frequent falls, such as rugby, risk bursitis. This, along with sustained pressure, is the most common cause of bursitis.
  • Severe trauma to the joint: any hard blow, as in a bad fall, may cause bursitis.
  • Bacterial infection of a bursa: this is more serious, and may, if left untreated, lead to more serious conditions such as septic arthritis, osteomyelitis and cellulitis.

What are the symptoms of knee bursitis?

Symptoms of knee bursitis vary according to the cause and the specific bursae affected. Common symptoms include pain if you move or put pressure on your knee, swelling and your knee feeling warm if you touch it.

If your knee bursitis is caused by bacterial infection, you will probably also experience fever. If so, consult your GP immediately.

Who is at risk of knee bursitis?

Several distinct groups risk knee bursitis:

  • Those with specific occupations or pastimes: people who put sustained pressure on, or risk frequent trauma to, their knees. This includes football players, all-in wrestlers and martial arts enthusiasts. People whose occupations necessarily involve frequent and sustained kneeling such as carpet-fitters and gardeners are also at risk of knee bursitis.
  • Those with specific medical conditions: the most important of these are osteoarthritis and obesity.
  • Those with an impaired immune system: these carry special risk of bacterial infection. People in this category include those suffering from diabetes, cancer and HIV/AIDS. People with alcohol or other drug abuse problems are also at risk. If you are diabetic and suffer from knee bursitis, see your GP immediately: the infection needs to be treated urgently.

How do I avoid knee bursitis?

Obviously, avoid prolonged kneeling and situations in which you are likely to fall or in other ways suffer trauma to your knees. If your occupation demands that you kneel frequently, wear knee pads. If you are an athlete, warm up using light aerobic exercise before engaging in vigorous physical activity. Remember that good muscle tone reduces the risk of any bursitis.

How is knee bursitis diagnosed?

Your GP will first perform a physical inspection. He or she will also want to know about your lifestyle and of any trauma that you think may have caused your problem. Your doctor may also wish to rule out other conditions that may be confused with knee bursitis such as bone fractures. You may therefore need one or more scanning techniques to inspect the inside of your knee – an X-ray, an MRI scan or an ultrasound scan, for example.

If your doctor suspects that infection is the cause of your knee bursitis, he or she may take a sample of your bursa fluid. This is termed aspiration and involves the drawing of the fluid by insertion of a hypodermic needle; this will probably cause short-term pain but the discomfort can be treated with an over-the-counter painkiller. The sample will then be sent away for analysis.