He said at 3 weeks post op, the rom you have will be all you will get.
Hogwash! At three weeks your leg is still swollen and angry. The ROM you have at three weeks is nothing close to what you'll get over time as the knee calms down from the assault that is a TKR, and begins to recover. The swelling will go down gradually; some of it is obvious as you can see it, some of the swelling is on the inside and not visible, but it's still there. Everyone heals at different rates, so to tell a patient that their ROM at three weeks is all they're going to get is not only ridiculous, it's a downright falsehood!
Think about what happens when you break an arm for instance. They put you in a cast for six weeks or so, to give the bone time to mend before allowing you to move it. During a TKR, they cut your bone off, and put a replacement where the bone was, along with slicing into all the tissues, muscles, etc, to get to the bone. They saw, hammer, screw, slice and dice your knee to repair the problem, which is much worse than a simple broken arm. And a doctor has the unmitigated gall to basically tell you that at three weeks your leg should be perfectly recovered and back to normal? Shame on him!
Your new implant is ready and waiting to give you a good ROM; the problem is your body needs to recover before you can take advantage of the new implant's mobility and motion. Even if your leg looks normal at an early point in recovery, you could still have swelling going on inside your knee that you can't see and is inhibiting your ability to bend and straighten fully. No matter what your doctor, or anyone else for that matter, says about where you "should" be at any given point in your recovery, your knee is the only one who can actually decide where it should be and no one can make it heal faster than it decides. You can, however, slow the healing down some by overdoing and over stressing an already stressed out body part.
My suggestion to you is to ignore that doctor's ridiculous comment about three weeks and just allow your knee to heal as it will. Continue to ice and elevate daily, and continue your daily activities as stated in this article,
https://bonesmart.org/forum/threads/activity-progression-for-tkrs.14334/ This was my favorite piece of information as I recovered; I read it daily to remind me not to do too much, or too little, at any given point in my recovery.
As for outpatient PT, I chose not to do any formal PT at all after my revision as, in my past experience, PT after a TKR, as it's practiced today in most cases, does more harm than good. My original plan was to only do a little formal PT down the road to help with my gait as it was off after limping for years, but I found I didn't need that either, so I did no PT whatsoever. My recovery after my revision was a miracle compared to my previous recoveries, and part of that I attribute to not pushing my knee to do more than it was ready to do, and not allowing anyone to guilt me into doing exercises or movements it wasn't ready to do. PT is entirely your decision to do, or not to do, and no one has the right to force or guilt you into doing it, only you can decide what's right for you and your recovery. If you want to do PT, do it, if not, skip it. It's your knee and your choice as to how you want to recover. We here at BoneSmart will support you whichever way you decide to recover, and only wish the best for you as you travel the path to taking your life back. Good luck and keep us posted!