I am a 61 year old male. I am not overweight and am in very good physical condition. I exercise daily with a mix of a stairmaster, indoor cycle, walking and weights. Besides exercise, I am and avid biker, sometimes skier, and do some rollerblading. My problem is when I walk more than 2 miles. At about the 2 mile point. the front inside area of my right knee begins to pain so much so I need to keep stopping. If my knee were the face of a clock the pain is around the number 4. It s difficult to get home but once home for 15 to 30 minutes the problem completely clears up. The knee has bee xrayed but nothing shows. This problem has existed for many years and is not very debilitating other than the longer walks. I do not have any difficulty with my exercise, biking, skiing or rollerblading. Do you have any ideas of what may cause this perplexing problem?