Alternatives to leg presses

Yes, no machines:

  • Squats
  • Lunges
  • Deadlifts (not too heavy; there’s a recent podcast mention of this on the return)
  • Step Ups (the height of your pedal stroke)
  • Standing calf raises (single leg if you can do it; holding weights even better)
  • Box jumps

Btw: I weigh 68Kg and years ago used to do sets of 10 x 150-200Kg on a leg press machine and learned what a mistake that was (the joint issues you mention). As I found out, you will be able to squat about 1/2 of that with a non-constrained barbell and get stronger. You can also start by using a smith rack (holds the barbell in horizontal alignment) until you get your form down well.