It's right. Your legs are the largest muscle groups and you can lift the most. By exercising the largest muscle group, and hard:
1. You use more energy
2. You increase / ramp up your metabolism both at the time and in the hours after.
3.You deliver a greater growth response / release of growth hormone.
4. The increase of metabolism and growth response means you will continue to burn calories
5. Your muscles will grow
6. Increased muscles will keep your metabolism higher.
So, in the long term weights workouts will produce a good response. But do also incorporate other muscle groups like back and chest. Best to cycle with some hiit for even better results.
Depends on what your goals are. I building muscle / definition /fat loss / cardio health. Assuming you're like me and most men: building muscle and definition.
Depending on time / how often you want to work out. I would hit compound exercises a few times a week and some hiit training on other days.
Squats followed by weighted lunges.
5 sets of 5 reps.
Then pull ups on one day.
Deadlifts and calf raises 5 sets of 5.
Then bench press another day.
Then perhaps another day of kettlebell swings, jerks, etc
One or two days,at least, of hiit
Say 30 seconds work, 10 second rest for 10 to 12 mins. Mix up the exercises but again recruit as many muscle groups you can:
Hindu push ups
Or do any of the above tabata style
Say mixing press ups with squat jumps. Then hollow hold and back raises.
Well then be careful.
Get the form right and you should be ok.
Maybe not too much hiit if you have dodgy knees but you still need to work it.
Maybe do cycling or rower instead.
Dodgy knees are tough, i did my acl, but you can do it and im better now after focussing on my form.