I cannot help, I'm not a doctor, but I can give you my thoughts. Is there a chance you can get a second opinion? Do you have free health, or good health insurance? Can you get to an actual hospital where you can tell the ER doctor EVERYTHING and see what they say? Again I'm not a doctor so I am not recommending or prescribing, but if I were you, I would maybe go to another pain specialist and ask about things like "nerve blocks" etc., because once your knee heals (eventually it will heal, right?), you don't want to now have a drug problem! And to clarify, your current pain doc may be doing everything right, so I'm just saying if I were you, I'd want a second opinion.
If you are seeing a Pain Management doctor, please express your concerns to them and they will balance your treatments accordindly. Don't do the self-medication with heroin though, doctors will not treat you in the future and self-medication is very dangerous.
If your pain is treatable by various means, your doctor will diagnose appropriately. The opioid method maybe temporary and is often a good solution, but you need to talk to your doctor.