My Knee Was Hurting When I First Get Up, And

My knee was hurting when I first get up, and going up stairs, mostly behind my knee. I went to a doctor and he said take ibuprofen 3 every 8 hours and do knee lifts because my knee cap was falling. 5 days later more pain, but moving to shin area. Limping badly, so I thought it might be from that? Female hairdresser 54, 260lb hairstylist , take B12 for gastric bypass