What is the reason for pain in the knee while playing?

Q: My son is 12 years old and plays tennis. Recently, about 4 months back he complained pain in his right knee while playing. The doctor suggested physiotherapy and rest. He attributes the cause of pain to the growth of some bone which he says is normal in kids when they are growing up. My son has stopped playing tennis. But, whenever he does play, he complains of pain. Can you please advise what could be his problem and possible treatment?

A:One of the commonest cause for anterior knee pain in this age group (when there is no h/o of injury) is traction apophysitis of tibial tubercle (Osgood Schattlers Disease) or inflammation at the region of the attachment of patellar tendon. Once other causes have been ruled out, activity modification with decrease in physical activity along with symptomatic treatment for roughly 6-12 weeks is needed. This problem is self limiting and disappears with growth completion.