adidas Boy's Tierro 13 Goalkeeper Pants

I got fed up with the splits in the knees of my boys trousers after only a couple of wears, so I've been hunting for padded or reinforced knees, these may be goalkeeper trousers, but my son wears them all the time and moans when they're in the wash.. The sizing can be confusing, but these fit my tall 4 year old with a bit of growing room, I would say these would fit an average height 5 year old.