Are you in PT? Hopefully you are and I think you should discuss your concerns with your therapist. Find out what their plan is for you. And if you don't get answers, talk with your surgeon. At 20 days, you are still very new to the recovery process and you have time to improve. ROM can be impacted by swelling....are you having swelling problems? Are you icing a LOT and elevatinig your knee above your heart? That will help reduce the swelling and possibly "free up" your knee to obtain better ROM. Also, a lot seems to depend on the state of your knee prior to surgery. Did you have limited ROM before? If so, then you have to really push past that and it may take longer. Sorry to throw so many questions at you, but progress depends on a lot of factors. Another really important one, as you've figured out, is pain control. It is much more difficult to have good PT sessions when you are in pain. I hope you can get that worked out! Keep pushing, though....it will get better!!!