After my knee surgery last year and therapy it took a long time and in small dribs & drabs to where I am now.
I started off with the resistance tubing very very slowly.
I used this band and incorporated the exercises from my therapy at home.
Slowly, I started using the elliptical trainer. Started off with about 3 minutes, then increased to 5, then 7 etc. Depending on how my knee felt that day.
I started to walk up the street very slowly since I could not walk to work which is a 20 min. walk for me.
Eventually, I was walking, had to force myself since taking a taxi to work for a couple of months was the only way to get to work.
What exercises I do not do are lunges & jumping jacks. Sadly, I gave my leg magic away as the motion of going sideways was too strenuous for my knee and not worth the pain.
Eventually, I had to go back to the specialist and get a cortosone shot which, so far, has been good for me, except, I still have the occasional bad day.
Now, I still have the same issue developing with my right knee. I hear it grinding. The only good thing is that the cartlidge has not snapped off while sleeping.