Hi. I'm a 27y/o male that has been experiencing problems getting and maintaining an erection. It started about a month after i had knee surgery January of this year. Before then I never had a problem. My diet isnt that good cause of work and neither is my sleeping habit and it was the dame before my surgery as well. I was into fitness a lot and was very active, but after my surgery its been hard getting back into lifting weights. I did see my pc and he prescribed me cialis. it works great, but once i stop using it I'm back to how i was. With my age he thought it was in my head. Could my surgery have cause this?