Runner's Knee (Chondromalacia Patella)

The cartilage under your kneecap is a natural shock absorber. Overuse, injury or other factors may lead to a condition known as chondromalacia patella - a general term indicating damage to the cartilage under your kneecap. Simple treatments - such a rest and ice - often help, but sometimes more complex treatments are necessary. (From mayoclinic.org)