How to build legs - without squats

Hi there,
At 57 I’m trying to keep a fit and healthy and will never race. I use TR as a foundation for any club rides or MTB-ing that i do throughout the year.
Recently had some work done on a knee (torn meniscus). Went to see the physio for a follow up as still having some issues and he basically said that I needed to bulk up my quads to strengthen the area around the knee.

So he suggested leg extensions and hamstring curls as I can’t at the moment fully squat. He aldo suggested jumping on a static bike, turning up the resistance and pedalling slowly for around 10 minutes to get to the point where i felt like my legs were made of jelly.

In light of this I have a few questions that I’m hoping some of you could assist with…

  1. If I cannot squat at the moment so all similar exercises are out (lunges, romanian deadlifts etc) is there a way to do seated leg extensions without going to a gym and second part will this build leg bulk?
  2. Are there any other exercises that folks think i could do - need to avoid weight through the knee so leg press also out.
  3. I cant think apart from threshold intervals and using a grinding slow cadence how I can achieve legs like jelly in order to build them up.

Wondering if anyone else had had similar issues around rehab and managed to work through them - if so, how?

And although I can’t squat that deeply I’m wondering if starting to will increase the range of loaded motion.

If I have to hit the gym so be it…but I’m financially tight (born n bred in Yorkshire) and mostly retired…

Cheers.
J.