My 14 Year Old Son Is Experiencing Knee Pain While

My 14 year old son is experiencing knee pain while playing sports. It is not Osgood Schlatters. He suffered from Osgood Schlatters for about 18 months while playing basketball and track. With proper stretching, icing, warming up, we have made it through this episode in his young life. The pain is only in his right knee and is located on the interior side of his knee under the surface. Different from his OS disease that was sore to the touch. This pain is more on the inside. Is there a common cause for this in terms of teenagers and strenuous activity.