Osgood-Schlatter's disease
Another common overuse injury is Osgood-Schlatter's disease. Although this condition usually shows up in the pre-adolescent ages, its symptoms of pain and tenderness often become more severe during adolescence, a time when the athlete is larger and more active in sports. Though it has a big name, Osgood-Schlatter's disease is just a painful bump over the front of the knee where the primary tendon (band of tissue that connects muscle to bone) of the knee cap attaches to the front of the lower leg bone (tibia). This point is a fulcrum, a power point for running, kicking and jumping. All of the pull of the quadriceps muscle comes through this attachment.

Osgood-Schlatter's ends as the adolescent matures and the growth plates close. The most important point I can emphasize about this condition is that, despite its name, it is not a disease. It is not dangerous; it does not lead to fracture or arthritis; and it does not require excessively aggressive treatment; it should not be treated with a cast or any form of stiff bracing.

There is no reason to make a child stop playing sports because of Osgood-Schlatter's, and there is no reason to operate on Osgood-Schlatter's in an adolescent. Treatments are ice, nonsteroidal anti-inflammatories as tolerated, knee pads to protect the area from being bumped, quadriceps stretching exercises, and activities as tolerated.

This material on Osgood-Schlatter’s Disease is from http://www.clevelandclinic.org/health/health-info/docs/0400/0448.asp?index=3902&src=news