Did you attend Boot Camp at San Diego NTC in the mid to late 1980s? In boot camp, while marching in formation, were you instructed to strike your left heel hard while marching at a cadence to create a kind of a "crack" or "click" sound? Did you notice the bevel on your outside left boondocker heel after a couple of months of marching? I ask because I remember that, and I also remember when around August 1986, they instructed us to cease that drill manuever. They said it was bad for our knees. I don't know if they did it out in the fleet, but I think the old guard at Arlington still does the same heel drop. Has anyone established a Nexus between this boot camp drill practice and later problems with knees, specifically left knees?