3 weeks is still early, I would give it more time. I will tell you if your knee is that irriatated now it will only be worse after the injection. Those injections always cause me more pain and swelling and I never have gotten relief from them. That being said though after you let your knee settle down and work on some physical theraphy if you are not feeling better, then trying the shots wouldn't be such a bad idea. You might ask for Euflexa, I think I read it is the only one not made from rooster combs. Some people on here say they work good for them, but most say it is a horrible experience. If it was to work for you it would be so much better than a tkr.