Osteoarthritis has been historically divided up into two different groups – primary and secondary – though this division is a little misleading, but that is neither here nor there.  Primary OA, by definition, is a little cloudy.  The simple version would be when OA forms in previously fine joints for what seems to be absolutely no reason and with no apparent initiating factor.  Primary OA is believed to be related to aging, as most people that have it are older.  It’s not directly related to aging though, because there is plenty of people that are in their 70s, 80s, and even 90s that have never had it.  Some clinicians limit primary OA to the joints of the hands.  Mainly the distal interphalangeal joints, proximal interphalangeal joints, and joints at the base of the thumb.  Some other clinicians also include the knees, hips, and spine as areas of potential involvement.

What are the Demographics of Primary OA?

Age: The occurrence of the disease increases dramatically after the age of 50.  80-90% of people over 65 are believe to have primary OA.

Sex: The prevlence of OA is higher amoung women then in men ages 55 and up.

Race: The patterns of primary OA are pretty different, and appear to affect certain races in one area, and another in a different area.