Definition of Bursitis:
A bursa is a closed fluid-filled sac that functions as a gliding surface to reduce friction between tissues of the body. Bursae is plural for bursa. The major bursae are located adjacent to the tendons near the large joints, such as the shoulders, elbows, hips, and knees. When a bursa becomes inflamed, the condition is known as bursitis. Most commonly, bursitis is caused by local soft tissue trauma or strain injury, and there is no infection (aseptic bursitis). On rare occasions, the bursa can become infected with bacteria. This condition is called septic bursitis.
What is knee bursitis?
The knee joint is surrounded by three major bursae. At the tip of the knee, over the kneecap bone, is the prepatellar bursa. This bursa can become inflamed (prepatellar bursitis) from direct trauma to the front of the knee. This commonly occurs when maintaining a prolonged kneeling position. It has been referred to as “housemaid’s knee,” “roofer’s knee,” and “carpet layer’s knee,” based on the patient’s associated occupational histories. It can lead to varying degrees of swelling, warmth, tenderness, and redness in the overlying area of the knee. As compared with knee joint inflammation (arthritis), it is usually only mildly painful. It is usually associated with significant pain when kneeling and can cause stiffness and pain with walking. Also, in contrast to problems within the knee joint, the range of motion of the knee is frequently preserved.
Prepatellar bursitis can occur when the bursa fills with blood from injury. It can also be seen in rheumatoid arthritis and can occur from deposits of crystals, as seen in patients with gouty arthritis and pseudogout. The prepatellar bursa can also become infected with bacteria (septic bursitis). When this happens, fever may be present. This type of infection usually occurs from breaks in the overlying skin or puncture wounds. The bacteria involved in septic bursitis of the knee are usually those that normally cover the skin, called staphylococcus. Rarely, a chronically inflamed bursa can become infected by bacteria traveling through the blood.
How is prepatellar bursitis of the knee treated?
The treatment of any bursitis depends on whether or not it involves infection. Aseptic prepatellar bursitis can be treated with ice compresses, rest, and antiinflammatory and pain medications. Occasionally, it requires aspiration of the bursa fluid. This procedure involves removal of the fluid with a needle and syringe under sterile conditions and can be performed in the doctor’s office. Sometimes the fluid is sent to the laboratory for further analysis. Noninfectious knee bursitis can also be treated with an injection of cortisone medication into the swollen bursa. This is sometimes done at the same time as the aspiration procedure.
Septic bursitis requires even further evaluation and treatment. The bursal fluid can be examined in the laboratory to identify the microbes causing the infection. It requires antibiotic therapy, often intravenously. Repeated aspiration of the inflamed fluid may be required. Surgical drainage and removal of the infected bursa sac (bursectomy) may also be necessary.
What about the other knee bursae?
A second bursa of the knee is located just under the kneecap beneath the large tendon that attaches the muscles in front of the thigh and the kneecap to the prominent bone in front of the lower leg. This bursa is called the infrapatellar bursa, and when inflamed, the condition is called infrapatellar bursitis. It is commonly seen with inflammation of the adjacent tendon as a result of a jumping injury, hence the name “jumper’s knee.” This condition is generally treated with ice, rest, and oral antiinflammatory and/or pain medicines.
A third bursa of the knee is called the “anserine bursa.” It is located on the lower inner side of the knee. This bursa most commonly becomes inflamed in middle-aged women. This condition is referred to as anserine bursitis. Anserine bursitis is particularly common in those who are obese. These patients can notice pain in the inner knee while climbing or descending stairs. Anserine bursitis is generally treated with ice, rest, and oral antiinflammatory and/or pain medicines, although cortisone injections are also given.