Landing with the foot in pronation causes the tibia to internally rotate, which can lead to the quadriceps shifting out of place and potentially an MCL tear.

“in a vus position is like this right so you land with the leg a little bit like this what this does we call this cond liftoff right so that's why you often see MCL tears because this gets stretched the cond lifts off of the surface and that surface on the inside of the knee this is called the medial part of the knee is very congruent it's the most congruent part of the knee the lateral side the surface of the tiia is convex it's very unstable in general so now you're only bearing weight basically on the unstable non- congruent part of the knee when you land when your foot lands in pronation by Nature the tibia internally rotates slightly at the same time that happens the quadricep pulls and then it shifts out of place”