Well Dean, going down steps is an eccentric contraction. I know you know what that is so I won’t describe it, for anyone that doesn’t know – click the link. You said your knee pops out of alignment, I’m assuming that means your kneecap. This movement is made better by strengthening the quads and hip abductors eccentrically. Here are all the eccentric exercises that I can think of for the quads. Step downs, lateral step downs, squats, single leg squats, anterior lunges, side lunges, posterior lunges, wall slides. That’s a pretty freakin’ cool website. knee extension eccentric, TKEs, walking backwards on a treadmill – do that very slowly – actually don’t do that. And hip abductors!