No way to perform Lunge

As i stated in the title as we talk about free lunge there is no problem.

As i tried to increase the weight e.g. 5 kg each hand i feel an all knee pain (where i got the surgery) when the knee is near the floor (so it's strange cause it is not pushing on the floor). the pain is not localized, it's all the joint.

What to do now?

If the single leg squat does not create problem can i do it weighted?

Or perform a similar exercise as wall SLS with the front leg far away from the door (here i feel the same activation in both glutes and quads as lunge)?

Can you do the lunge with no weight at all? 

Yes with no weight there is no problem, i repeat that the strange thing is that the pain in the knee is when the leg is not actively involved in the pushing movement but when it is assisting the movement of the left leg. i tried different legs distance, it's only bad. The pain is soft and it increases as I move closer the knee to the floor.

I would find the heaviest weight you can do without pain, then take off 10%, and work up until you're at 5x5 without pain. Then gradually increase the weight. This is how I was working through the HBP progressions when my shoulder was injured. 

What about split squats and step-ups?

split squat are ok, now i can do them, i'm healing from a pubalgia but i don't think they are effective as the lunge in the butt activation. i'm referring to sumo squat with split squat. it' more an adductors activation.

Look up bulgarian split squats (like a lunge but with the back foot raised). Activates my butt like nothing else. Sore for days every time I try them. They take a decent amount of balance and stability too. Though - they may put a similar kind of pressure on your knees... try them out with a light weight I guess?

the exsecution is very similar, nothing changed..

Hmm unfortunate. I started developing a pain in my knees doing Natural Leg Extensions (SLS/Pe4>iM) at the end of the ROM and it turned out to be tight quads. Regular foam rolling with a Rumble Roller  got rid of it for good.