Knee bursitis is inflammation of a bursa located near your knee joint. A bursa is a small fluid-filled, pad-like sac that reduces friction and cushions pressure points between your bones and the tendons and muscles near your joints.
Each of your knees has 11 bursae. While any of these bursae can become inflamed, knee bursitis most commonly occurs over the kneecap or on the inner side of your knee below the joint.
Knee bursitis causes pain and can limit your mobility. Treatment for knee bursitis often includes a combination of self-care practices and doctor-administered treatments to alleviate pain and inflammation.
Knee bursitis signs and symptoms may vary, depending on which bursa is affected and what precisely is causing the inflammation.
In general, the affected portion of your knee may feel warm, tender and swollen when you put pressure on it. You may also feel pain when you move or even at rest.
A sharp blow to the knee can cause symptoms to appear rapidly. But most cases of knee bursitis result from repetitive injuries — sustained in jobs that require a lot of kneeling — so symptoms usually begin gradually and may worsen over time.
When to see a doctor
The bursa that lies over your kneecap can sometimes become infected. Call your doctor if you have a fever in addition to pain and swelling in your knee.
Knee bursitis can be caused by:
Frequent and sustained pressure, such as from kneeling
A direct blow to your knee
Bacterial infection of the bursa
Complications from osteoarthritis, rheumatoid arthritis or gout in your knee
Knee bursitis is a common complaint, but the following factors may increase your risk of developing this painful disorder.
Excessive kneeling. People who work on their knees for long periods of time — carpet layers, plumbers and gardeners — are at increased risk of knee bursitis.
Participation in certain sports. Sports that result in direct blows or frequent falls on the knee — such as wrestling, football and volleyball — may increase your risk of knee bursitis. Runners may develop pain and inflammation in the anserine bursa, located on the inner side of your knee below the joint.
Obesity and osteoarthritis. Anserine bursitis, affecting the inner side of your knee below the joint, often occurs in obese women with osteoarthritis.
You can take steps to avoid knee bursitis or prevent its recurrence:
Wear kneepads. If you're working on your knees or participating in sports that put your knees at risk, use padding to cushion and protect your knees.
Take breaks. If you're on your knees for an extended period of time, take regular breaks to stretch your legs and give your knees a rest.
Avoid excessive squatting. Excessive or repetitious bending of your knees increases the force on your knee joints.
Doctors often can make a diagnosis of knee bursitis during a physical exam. Your doctor will inspect your knee by:
Comparing the condition of both knees, particularly if only one is painful
Gently pressing on different areas of your knee to detect warmth, swelling and the source of pain
Carefully moving your legs and knees into different positions to determine the range of motion in your knee joint and identify movement associated with pain
To help rule out injuries that may cause signs and symptoms similar to those of bursitis, your doctor may order one or more of the following imaging tests:
X-ray. While they can't visualize bursae, X-rays may be useful in revealing a bone fracture, tumor or arthritis.
Magnetic resonance imaging (MRI). MRIs use radio waves and a strong magnetic field to produce detailed images of structures within your body. This technology is particularly good at visualizing soft tissues, such as bursae.
Ultrasound. Using sound waves to produce images in real time, ultrasound can help your doctor better visualize swelling in the affected bursa.
If your doctor suspects that you have an infection or gout in the bursa, he or she may obtain a sample of the bursa fluid for testing by inserting a needle into the affected area and draining some of the fluid.
Depending on which parts of your knee are affected, your doctor may recommend one or more treatment approaches.
If an infection has caused the knee bursitis, your doctor will prescribe a course of antibiotic treatment.
Your doctor may refer you to a physical therapist or specialist in sports medicine, who can help you learn appropriate exercises to improve flexibility and strengthen muscles. This therapy may alleviate pain and reduce your risk of recurring episodes of knee bursitis.
Surgical and other procedures
More invasive treatments for knee bursitis treatment may include:
Corticosteroid injection. If the bursitis is persistent and not responding to basic treatments, your doctor may consider injecting a corticosteroid drug directly into an affected bursa to reduce inflammation. The inflammation usually subsides rapidly, but you may experience pain and swelling from the injection for a couple of days.
Aspiration. Your doctor may aspirate a bursa to reduce excess fluid and treat inflammation. He or she will insert a needle directly into the affected bursa and draw fluid into the syringe. As with a corticosteroid injection, aspiration may cause short-term pain and swelling, and you may need to wear a knee immobilizer for a short period after the injection to reduce the chance of recurrent swelling.
Surgery. If you have severe chronic bursitis and don't respond to other treatments, your doctor may recommend that the bursa be removed surgically.