Cartilage in the knee cap is the thickest in the body for a reason - it gets a constant beating, at least from some athletes. The knee bears up to eight times your body weight going up and down stairs and in activities like jumping.
     For athletes, the intense wear and tear can erode cartilage – causing the knee cap to no longer glide easily. Kneecap cartilage is hard to repair, but at Vanderbilt University Medical Center, doctors are improving outcomes for athletes by making nearby bone bleed.
     Barb Cramer has the story.