My 13 year old son was told he has tendonitis in hamstring. He can not sit up staight when he sits on the floor with his legs out in front of him. He also can not bend over because of the pain in the muscle behind his knee. The doctor told us to have him stretch 2 times a day for 5 to 10 min. Also to use a heating pad. He stats baseball this week. the Doctor said this was O.K. What can you tell me about tendonitis. I tryed to find info on the net but all I got were sponcers ad trying to sell something. Thank you for your help?