Causes of bursitis

Bursitis candevelop in three main ways. It can be caused by an injury or infection, oras the result of a pre-existing health condition.

Injury

If a bursa(the small fluid-filled sac which forms around the joints) is injured, the tissue inside it can become irritated, leading to inflammation (swelling).

In most cases, the injury develops overtime because joints, muscles and tendons near the bursae are overused. Repetitive movement is a particular risk for this type of injury.

Waysthat the bursa can be injured include:

• lifting or reaching overhead can damage the shoulder
• repeatedly bending and straightening the elbow, or falling on it
• repeatedly moving the kneeor kneeling on it(bursitis of the knee is known as "housemaid's knee")
• excessive walking (particularly if you are not wearing suitable walking shoes) or activities such as ice skating or athletics can damage the ankle
• running can injure the hips
• leaning your elbows or kneeling on hard surfaces

Abursacan also be injured following a sudden impact, such as banging your elbow or by falling heavily on to your knees.

Infection

Bursae near the surface of your skin, such as those near your elbow, can become infected if bacteria find their way into cuts and grazes and then move into a bursa. Bursitis caused by an infection isknown as septic bursitis .

The immune system (the body's natural defence against injury and illness) usually prevents this typeof infection, soseptic bursitis tends to only occur in people with a weakened immune system. This can bebecause ofa long-term condition, such as HIV and AIDS , or takingcertain medication, such as corticosteroids or chemotherapy . Alcoholism, diabetes and some kidney conditions canalso put people at a higher risk.

Health conditions

Anumber of health conditions can sometimes cause a bursa to become inflamed. These include:

• gout and pseudogout a condition caused by a build-up of uric acid in the blood
• rheumatoid arthritis where the immune system attacks the linings of the joints
• scleroderma a condition that causes hardening of the skin
• ankylosing spondylitis a type of long-term arthritis that affects parts of the spine
• systemic lupus erythematosus a poorly understood condition that affects many of the body's tissues and organs
• being overweight can also cause bursitis