Easier on the knees, just as savage for the legs.
Step straight back, not out wide. Your front shin should stay close to vertical.
Stepping backward instead of forward keeps your front shin close to vertical and your weight planted through the front heel, so the quads load hard without the knee drifting over the toes. The glutes assist on the front leg, controlling the descent and powering the drive back to standing. It earns its place as the lunge most people should start with, all the single-leg benefit with far less knee complaint and less balance chaos than stepping forward.
Stepping back means no braking force on the front knee, it stays stacked over the ankle while you drop straight down. Forward lunges make the knee absorb your momentum, which is where the complaints usually come from.
Get it close, a light kiss is fine but no crashing. Lowering under control to just above the floor keeps tension where it belongs and saves your kneecap.
Step straight back rather than angling behind your other leg, like your feet are on train tracks, not a tightrope. Slowing the descent down also gives your stabilisers time to do their job.
