Hi and welcome.
One possibility is PMR as swelling along with joint and muscle stiffness and pain is associated with it. Your kidney , liver, thyroid and adrenal functions should be evaluated to rule out anything related to these organs. If your doctor has reached on conclusion that your diagnosis is PMR and other tests are normal then follow up with him so that its treatment can be started. Keep check on your blood pressure as well. Restrict salt intake and add more proteins in your diet.
Autoimmune disease should be ruled out by testing auto antibodies.
Let me know if you have further questions.
Please do not forget to leave a positive rating by clicking on the stars on top of the screen.
Wish you good health.