Bursitis can be caused by an injury, an infection, or it can be the result of a pre-existing health condition that causes the bursa to become inflamed.
Bursitis can develop in three main ways. It can be caused by an injury or infection, or as the result of a pre-existing health condition.
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 over time because joints, muscles and tendons near the bursae are overused. Repetitive movement is a particular risk for this type of injury.
Ways that 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 knee or 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
A bursa can also be injured following a sudden impact, such as banging your elbow or by falling heavily on to your knees.
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 is known as septic bursitis.
The immune system (the body's natural defence against injury and illness) usually prevents this type of infection, so septic bursitis tends to only occur in people with a weakened immune system. This can be because of a long-term condition, such as HIV or AIDS, or taking certain medication, such as corticosteroids or chemotherapy. Alcoholism, diabetes and some kidney conditions can also put people at a higher risk.
A number 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