I have never heard that one before,interesting.but it could also be some sort of structural problem within the actual knee.If this just suddenly became painful it really does need to be looked at by your primary doc and then have you sent for an MRI on that knee if he feels this is more than just a bit of wear and tear.i do believe that the knees are the number one most injured area when someone is involved in sports.espescially when you are doing alot of running,and not always on good surfaces.just think about all of the weight that is slammed down onto the feet and the knee everytime you run.that is alot of force to have slammed onto a body part over and over and over.There could be many dofferent possibilities that could cause the type of knee pain you are actually describing.i have one knee that has about five seperate problems most of them I diod not even know that these were even there til I had to have an MRI done because the pain was really getting to severe to just live with.The MRI actually showed and 'old' sprain which I had no clue how or when this even occured.there are all kinds of things that can be wrong with any knee.tears in ligaments and cartlidge,bone on bone problems or a condition called chondromalacia which is the desintigration of cartlidge just from wear and tear.i have this behind my knee cap among other things,and the entire backside of my knee cap is currently shredding.You really DO need to have this evaluated by your doc and see just what he/she wants to do or thinks it may be.chances are,if this remains painful or any swelling develops,you may be getting that MRI.which really IS the best way to actually see just what IS going on in there.you could have just caused a very small sprain or some other rather mild issue but it does need to be looked at at any rate.If there IS any sort of problem you need to have this treated sooner rather than later,espescially if you are really into running or any other type of sport,you do not want to do anything to cause any big starin or do any running anymore til you have had the okay from your doc or you could cause some very bad damage.Good luck and let me know just what you find out.take it easy on that knee,and don't walk too much on it if it causes any moderate to severe pain.trying something like aleeve and cold packs should work really well for any pain.FB