Knee problems related to Osteoarthritis and Psoriasis

Dear Ask The Doctor: I was diagnosed with psoriasis 26 years ago at the age of 19. Two years ago I had my right knee replaced. The orthopedic surgeon stated that I had OA and that was the reason for the damage to my knee. I asked if it was possible that I had PsA and he stated that my knee showed no signs of inflammation or swelling which would rule out PsA. Recently I had arthroscopic surgery on my left knee to clean up some loose pieces and the problems became worse after the surgery. During my post-op meeting I discussed PsA with the PA and she stated it is very possible. I met with the doctor a week later and asked him again, could PsA be part of the reason why my knee is damaged at such a young age . His answer was the same, no inflammation or swelling, no PsA. He did run blood test; sed rate 0, RA Latex 10.3, CRP 1.5. Prior to the blood test I did have a cortisone shot and my weekly enbrel injection, so I'm not sure if that effected the results. I've decided to have TKR of the left knee and will be having it in approximately 3 weeks. I also decided to see a Rheumatologist to have some of my questions answered. I had x-rays taken and blood work. He diagnosed me with Psoriatic Spondyloarthropathy Sacroiliitis Based on my blood work I have Chrohn's Disease, but he would like me to have a colonoscopy to verify the results. I asked him the same question I asked the orthopedic surgeon. Could PsA be part of the issue with my knees having to be replaced at such a young age. He said it is "very possible", based on my age and the number of years I've been dealing with psoriasis outbreaks, but because the OA had taken over, it would be difficult to say without a doubt yes. Is there a test that could show that there is at least a 50% probability that the damage was due to PsA.

Dear Bill: Psoriatic arthritis is a form of arthritis that affects some people who have psoriasis. Joint pain, stiffness and swelling are the main symptoms of psoriatic arthritis. They can affect any part of your body, including your knees, fingertips and spine, and can range from relatively mild to severe. In both psoriasis and psoriatic arthritis, disease flares may alternate with periods of remission. No cure for psoriatic arthritis exists, so the focus is on controlling symptoms and preventing damage to your joints. Without treatment, psoriatic arthritis may be disabling. In your case I think that the Psoriatic arthritis caused your problem and then the degenerative changes in the joints due to aging process osteoarthritis worsen the situation. No single test can confirm a diagnosis of psoriatic arthritis. But some types of tests can rule out other causes of joint pain, such as rheumatoid arthritis or gout.  Rheumatoid factor (RF) is an antibody that's often present in the blood of people with rheumatoid arthritis, but not usually in the blood of people with psoriatic arthritis. For that reason, this test can help your doctor distinguish between the two conditions. Using a long needle, your doctor can remove a small sample of fluid from one of your affected joints , often the knee. Uric acid crystals in your joint fluid may indicate that you have gout, rather than psoriatic arthritis. Plain X-rays can help pinpoint changes in the joints that occur in psoriatic arthritis but not in other arthritic conditions. Sed rate, or erythrocyte sedimentation rate (ESR), is a blood test that can reveal inflammatory activity in your body. A sed rate test isn't a stand-alone diagnostic tool, but it may help your doctor diagnose or monitor the progress of an inflammatory disease.