So let me start off by saying I don't have any knee pain.
I run a lot 20-30 miles a week and usually end up squatting or doing something involving my legs (Crossfit) 2-3x a week. In my running I do some downhill work (maybe 1.5-1.75 miles downhill). I never feel pain, but my knees surely are creaky from time to time or sore, like I can tell they have done work/taken a pounding. Is this something to be worried about? Is it the volume of leg work, weak hamstrings? Thanks.