A bursa is a small sac filled with fluid. You have many bursae (the plural of bursa). Bursae cushion your muscles, tendons, and ligaments around joints and keep them from rubbing against each other.
What is bursitis?
Bursitis is inflammation of a bursa.
The bursa swells up with fluid
Sometimes the swelling is red and tender to touch
Bursitis may not hurt, it may hurt only when you move the joint, or it may hurt all the time
Bursitis happens most often in the shoulder, elbow, and hip but can also affect your knee, toe, or heel
Doctors treat bursitis with rest, splints, pain medicine, and corticosteroids
What causes bursitis?
The most common causes of bursitis are:
Overuse of a joint, usually moving it the same way over and over again
Putting constant pressure on the same area, like working on your knees or leaning on your elbow a lot
Other causes of bursitis include:
Injury
Infection
What are the symptoms of bursitis?
Symptoms of bursitis can come on suddenly or build up over time. They may come and go. They can include:
A painful swelling around a joint
Swelling that may be red or your normal skin color
Sometimes pain when moving the joint
What are the complications of bursitis?
Sometimes the bursitis fluid gets infected by bacteria. Infection makes the redness and pain much worse.
How can doctors tell if I have bursitis?
Doctors can often tell you have bursitis based on your symptoms and examination. They may:
Use a needle to take a sample of fluid from the swollen bursa to check for infection or gout
Most of the time you don't need any other tests, but sometimes doctors will:
Do x-rays Plain X-Rays A plain x-ray is an imaging test that takes a picture of the inside of your body. It uses a low dose of x-ray radiation. X-rays show body parts according to how dense (solid) they are. Doctors... read more
, MRI Magnetic Resonance Imaging (MRI) MRI is a test that uses a machine with a powerful magnet to make pictures of the inside of your body. A computer records changes in the magnetic field around your body. The computer then uses... read more 
, or ultrasound Ultrasonography Ultrasonography is a safe imaging test that uses sound waves to create a moving picture of the insides of your body. Ultrasonography doesn't use radiation (x-rays). Ultrasonography is also called... read more 
Do blood tests to check for other diseases
How do doctors treat bursitis?
If your bursitis isn't caused by an infection, doctors will have you:
Rest
Use a splint to keep your joint from moving
Put an ice pack on the painful area
Take a nonsteroidal anti-inflammatory drug (NSAID) such as ibuprofen or other medicines for pain
Do physical therapy or exercises to help your joint move more freely
Sometimes doctors will drain the fluid in the bursa with a needle. They may inject the bursa with medicines such as corticosteroids to lessen the inflammation. If the bursitis doesn't go away or keeps coming back and is still causing problems, doctors may suggest surgery to remove the bursa.
If a bursa is infected, doctors will:
Drain the fluid
Prescribe antibiotics
Doctors will treat the cause of your bursitis. It's important to do this so your bursitis doesn't come back.
