My joints are sore mainly my knee is really sore and hurts when i stretch it out.dad has rheumatoid & osteoarthritis. could i have this? im 21.

Possibly: Pain is one thing and pain and swelling are another. If there is joint swelling, the possibility of RA is much higher. See a rheumatologist for the answer.

Maybe : At age 21, osteoarthitis is unlikely. Because your father has ra, that might be a possibility in a 21 year old female. If you have morning stiffness, persistent soreness, and particularly if there is joint swelling, see a doctor. If there are still questions, consult a rheumatologsit.