Stiff Joints but only a Teen

I am 19 and healthy, five foot one and 125 pounds, and I walk wherever I have to go during the week (I live on a small campus), I only drive on the weekends. I drink lots of water and milk, no pop or caffiene during weekdays. But whenever I sit cross-legged or even if I just stay in one position too long, I get painfully stiff joints, especially my knees and ankles and occassionally my wrists. It's difficult to move again once they become stiff until they relax and loosen up again. In addition, I've suffered from back pain for the last two years or so, which is worst in my lumbar region. My spine bulges out just above my buttocks, where my back is always stiffest. Am I just getting old while I'm still young? Why is this happening? I'm not dehydrated or anything, and I'm pretty sure I don't have arthritis because I don't know why I would. My dad's family has a history of bad backs, but not bad joints as a teenager. Should I be concerned? And how can I lessen the problems?

[margypops]

well it may not be a concern you may still be getting growing pains , but I think for your peace of mind it would be good to go to the Doctor., you say you have had back pain for two years ,did you get that checked out?

[CCFHeartMD11]

Joint pains at a young age could indicate a rheumatologic process, such as rheumatoid arthritis or ankylosing spondylitis. Features consistent with these diagnoses are pain that is worse after resting, morning stiffness lasting longer than 30 minutes. It would be reasonable to see a primary care doctor (or student health) to have your joints examined, some bloodwork sent, and maybe some Xrays.

[stacmann3]

you should get checked for arthritus it isnt just for old people, also fibromyalgia, go see a chiropractor and see if your out of alignment