Stuff my shoes with socks: Why do my Knees Hurt?

I stuff a sock as a lifter to step on inside my shoes and make me look taller for about a year now. recently my knees have been hurting and when i walk downstairs there are pains in my knees. The pain is mostly under my kneecap. Does anyone have an explanation and will the pain go away if i stop stuffing my shoes with socks under my heel? Thanks!