I've had "bursitis" for many years that began in one knee only. Now it is in both knees, hips & from my knees up to my hips on the outer side.
I had a bone density which only came back w/ osteopenia.
So the dumb question is could it be arthritis even though the density came back minor?
No question is dumb. The most usual way to diagnose osteoarthritis is with ordinary x-rays, which show up the changes in the joint. Other symptoms can include pain, stiffness, changes in range of motion, reactions to changes in the weather, and those annoying sounds when you move like clicks, a little noise or feeling that sounds like crinkling tissue paper (crepitus).
My RA was diagnosed by a bone scan that lit up like a Christmas tree, and my sed rate was high. You may want to ask for those and a RA factor blood test-however, this test is not conclusive (25-30% of patients with RA test negative for RA factor). If you are having chronic pain in multiple joints that is progressing, you really need to follow up with your doc.