Is it possible to have oa and ra at the same time?

Yup.: osteoarthritis, or "OA" is a common maturational change of the skeleton, usually with aging or history of repetitive trauma. So this can happen to anyone- even people who also have RA, or rheumatoid arthritis, which is an autoimmune condition that has somewhat different presentation, blood test results, and treatment. Even folks with RA get older, and we do often see a mixed pattern of arthritis.

Possible...but: Over time whichever joints had been affected by OA previous to the Dx of RA will be eventually attacked by the autoimmune system and you may not see much evidence of OA after a period of time.