65 Y/o White Female With Multiple Sclerosis & Psoriatic Arthritis.

65 y/o white female with Multiple Sclerosis & Psoriatic Arthritis. Bending at waist today (12:30 p.m.) to remove right shoe, heard loud popping noise and felt shifting and pain inside right buttock. Still hurting and pain all the way into the right calf muscle. Is this something I need to go to doctor about? What happened? Felt like something went out of place (I have a knee that pops and goes out of place from time to time).