My son is 39 yrs old and has had a swollen foot for 3 months. He has been to many doctors and they have guessed it is arthritis; don't know-but it's inflammation; no fluid is in the swelling; ex-rayed the foot; sonagramed the foot, and it still has swelling and pain. Could this be "RSD"? How do I get a doctor to diagnose this med condition properly? Please help. He is self employed and cannot work when pain is bad.