What Causes Pain In Thighs And In Tailbone?

The pain in my thighs is concentrated underneath the knee and in my tailbone the pain is so severe just sitting on a chair that I can only tolerate it for a short periods of time before I have to get up and try to walk it out. I think I have developed rheumatoid arthritis which is felt in all my joints at present. I am waiting for blood tests from my doctor and hope there is remedy, as at least some relief. Am 81 yrs of age and have led a very active life. (Skiing tennis,golfing and hiking. Would appreciate your take on this, thank you.