Persistent Knee Swelling

Okay, that's helpful information. Your knee swelling could be related to one of the following:

If you have had psoriasis in the past, your knee swelling could be due to psoriatic arthritis, a form of joint inflammation that occurs in about 10-20 percent of people with psoriasis. If psoriasis affects your nails, the chances of arthritis are even higher, about 50 percent. Usually, there is only one joint or a few joints affected (rather than six or more, as in rheumatoid arthritis), and the knee is often one of them.

If you have had colitis, such as Crohn's disease or ulcerative colitis, in the past, or if you have suggestive symptoms, including chronic diarrhea, bloody stools, and cramping, it is possible that your knee swelling is related to colitis-associated arthritis. This type of joint inflammation affects about 10-20 percent of people with these types of colitis. As with psoriatic arthritis, there is usually just one or a few joints affected (rather than six or more, as in rheumatoid arthritis), and the knee is often one of them.

If you have pain and swelling in other joints, including the other knee and the hands and wrists, rheumatoid arthritis is a real possibility. Joint symptoms tend to be much worse in the morning. Arthritis due to a viral infection can mimic rheumatoid arthritis except that it tends to go away within 3-6 weeks (and often sooner).

Sometimes, despite a thorough review of the circumstances surrounding your knee swelling, a full examination, and, perhaps routine x-rays, the cause of your swelling may not be clear. If it persists and is associated with significant symptoms (pain, instability, or locking, for example), your doctor may recommend one or more of the following tests:

tapping the joint for synovial fluid analysis - after numbing the skin, a needle is inserted into the knee and joint fluid is removed; the fluid is sent to the laboratory for analysis, including the number and type of white cells (measures of inflammation), tests for infection (called gram stain and culture) and inspection under a special microscopic looking for crystals (as seen in gout or pseudogout)

• MRI - a large magnet is used to create pictures of the inside of the knee, including bones, cartilage, ligaments and tendons

• CT scan - a specialized series of x-rays that create a three-dimensional picture of the knee

• arthroscopy - a tube with a light and camera on the end, roughly the size of a pencil, is inserted into the knee to directly view the interior of the joint; certain abnormalities, such as damaged cartilage or a loose bone fragment, can be repaired with this instrument.

Regardless of whether any of the conditions reviewed in this guide seem to fit your situation, contact your doctor for evaluation and follow-up. Even if the cause is uncertain now, a diagnosis may be much clearer over time.

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