Bursitis generally occurs in the very front of the knee. This is known as pre-patellar bursitis because it is in front of the patella, or kneecap. Notably, the bursa does not communicate with the joint proper. The bursa is a sliding sack that allows tissues to glide across one another. There are two other bursae around the knee below the joint line. On the inner side of the knee the pes anserina bursa is overlying the attachment of the hamstrings (sartorius, gracilis and semitendonosis tendons) and over the lateral side of the knee is a bursa at the insertion (attachment) of the iliotibial band. These tend to not get as enlarged or swollen. It can be the site of annoying pain in runners particularly if they have been going over a lot of irregular terrain. This is an inflammatory problem generally occurring because of repetitious and/or prolonged kneeling. Occasionally a bursa will become extremely inflamed from accumulation of urate crystals in a person with gout. Other people via a small abrasion or tiny puncture in the skin will develop staph or strep infection.
In the case of a person who comes to the doctor with severe pain, swelling and redness known as erythema, a doctor must determine whether this is, in fact, infection or just bad inflammation. In this setting it is important to insert a needle into the bursa and withdraw fluid. The fluid is sent to the laboratory and looked at under the microscope for bacteria and crystals. Negatively birefringent crystals indicate gout. Most of the time an infection of bacteria will not be seen because there will be so many white blood cells, but within 24 hours a culture will grow out bacteria. Generally with infected bursitis it is best to withdraw the pus with a large bore needle because it is thick. Cutting through the skin with a scalpel making a significant wound to drain infection from a bursa is generally not a good idea because it will keep draining and takes a long time to heal. A series of needle punctures over the course of a couple days plus antibiotics are the treatment of choice.
For non-infected (aseptic) bursitis, cortisone injection is often very beneficial or in a person who is averse to injection cortisone iontophoresis, transfer of the cortisone via electrical impulse which is much less efficient because less medicine crosses the tissue this way, can also be utilized. NSAID such as meloxicam, naproxen sodium or diclofenac are a slower way of treating it but perhaps better suited for supplementing the corticosteroid in a person who really needs relief.
The patient’s photo here is a young woman in her 30s with simple, non-infected prepatellar bursitis. After it didn’t respond to cortisone injection, under local anesthesia with a little sedation and a small puncture wound the tissue was trimmed with an arthroscopic shaver as an outpatient with minimal postoperative discomfort.