I agree with everything Magnus stated above.
I recently had my knee replaced ( 22 Feb 2019 ). I did no preconditioning before surgery and I do not think it effected the outcome at all. I was back at work ( not a desk job ) 5 weeks & 3 days ( 03 Apr 2019 ) after my surgery. I did do 4 weeks of post op physical therapy three times a week. I also did home therapy every day on my own with suggestions from my therapist.
These are the stages I had after surgery:
Week 1 - Using a Walker.
What the hell have I done to myself? Gimping around with a walker, hard to use the toilet and lots of pain. Hint: Take the pain pills before you need them. It is easier to stay ahead of the pain than it is to catch up after it starts. Lots of icing to help with swelling. Get an ice machine! This is what I used, but I got it through the doctor and it was cheaper:
https://www.healthproductsforyou.com/p-breg-polar-care-cube-cold-therapy-system-super-saver-combo-pack.html?msclkid=fa40e0e00ea711fa7bcebd81e95f911c&utm_source=bing&utm_medium=cpc&utm_campaign=Specialties-Physical Therapy Shopping&utm_term=4580771606099683&utm_content=Cold Therapy Cold Packs New
Week 2 - Stepped up to a cane. Pain is better, but gets more intense when sleeping or trying to sleep. Getting around is easier, but I tired easier and sooner than I normally would. Doing better but still wondering if I did the right thing.
Week 3 - Doing much better and actually sleeping through the night with no pain medications at all. The knee only hurts if I overdo my walking or if I twist my knee inadvertently. Still using the cane. Started using the stairs again and driving.
Week 4 - Walking without a cane painless for the most part. Can go up stairs without a handrail and actually climbed a ladder just to see if I could. Knee at this point feels better that the old real knee has in 10 years.
Week 5 - Everything is pretty much normal with the exception of I cannot put that knee on the floor as the knee cap is very sensitive to the pressure. There is still a lot of internal healing left to do. The doctor says it takes about 12 months to be fully healed.
Week 6 - Back at work! The knee replacement and cataract surgery in both eyes are the best two things I have ever done for myself.
I wish you all the best. I hope you have an excellent surgeon as that is the biggest part of your outcome to get the length and angle correct. The rest is up to you.
If you have any questions reply back to this thread and I'll share what I know from my experience. Of course everybody is different.