Slipped your right leg high. Exhale, step your foot between your hands and drop your back knee down towards the floor. Walk both hands up toward your front. If you're hearing anything from your back knee, if it's even whispering at you, just take a blanket, take some sort of support. You can even wrap your mat onto it's side and use that on the knee. Always protect the knees. We want to listen for the little whisper so it doesn't turn into a scream later.
So, pad the knee if you need it. Walking both hands onto your front thigh, using your hands, like literally walk your hands back to where the hip creases and start to scrub the muscles forward to create more space here. And you'll see that I'm pretty directly over this back knee so I can use my tailbone. If I'm leaning forward into a full lunge then I can't use my low belly and my tailbone to help stabilize. So, I'm going to come out of the lunge a little bit. Use the tailbone, use the low belly to help support, and then you can rebend the front knee accordingly. Tuck your back toes underneath and then lift the back knee up towards the sky so you're in a high lunge.
So you went from a low lunge to a high lunge. Tailbone stays active. Back knee stays straight, and then you can reach your arms up and over head. Waist lines carry back. Super common to come into this pose like this where the rib cage is popping forward and the low back is compromised. So, again, taking the waist lines, working them back and space tail bone down, straightening the back leg and then the arms up and over head. And we've got your yoga lunge. Exhale, hands to the floor. Stepping back, downward facing dog.