Bones and joints, knees is a fun thing, yeup going up and down stairs is blast! I have a left foot that makes a crackly n pop noise here also. I think its from shifting dirt bikes for more than 30 years. My name is Hondabro, and im a dirt bike addict! Any time a nice change in weather hits, this bro feels it! Do you gents have some old dude stuff, like worn joints or snapped bones. You know you are a dirt bike rider if you have em'!