I'm 4 months post- TKR, was in great shape, and did PT prior to surgery to help post-op rehab, so your experience may be different. Just some quick thoughts:
1. TAKE YOUR PAIN MEDS! Cannot stress this enough. Stick to the schedule, do not play catch up or be a tough guy: the bone pain is for real (for about a week or so in my case and quickly gets 'better').
Making sure you take them is also imperative for starting PT. There is a new drug, non opioid, called Journavx, you can talk to your surgeon about. Worked well for me after I stopped the opioids. Honestly, the opioids prescribed help tremendously, but the constipation is also for real, so make sure you take the miralax or whatever he prescribes.
2. Ice and elevate (ie knee above the heart) religiously to mitigate the swelling. (I thought I could get away with just sitting in a chair with knee up on a coffee table a couple weeks after, but my lower leg/ankle swelled like a champ and when I went back into PT, he said I HAD to elevate above heart as that swelling can lead to blood clots.)
3.Get PT scheduled ASAP if not already. The most important thing is getting that knee moving: bending/straightening. So at home, do the heel slides, quad sets, the ankle pumps etc often per surgeon direction, and using your walker, slowly walk around the house practicing walking correctly. It will feel weird as heck, as your quad has shut down, and all the proprioreceptors in you knee have been screwed up, so focus on flexing that quad when you take a step.
4. It is a slow process. Its crazy how long it takes for the quad to 'wake up'. Don't get discouraged as you will see progress almost daily. Don't be afraid to move it; you won't break it. Yes, its gonna be tough and uncomfortable, even painful. As my PT says, 'motion is lotion.'
Good luck!