Hi! I've been on methadone for over 2 years for intractable spinal pain & a few months ago my knees went wild with pain. Filled one with synovial fluid, can't bend or lean on anything, et. Read vitamin d deficency can cause this as 80% of meth users have this & it'''''''''s not due to "methadone getting in the bones". I don't know 'cause I can't afford mri, but I figure I'll pick up some vit D. Love & feel better