My 7 yr old son walks on his tip toes ?

He walks on his tip toes and is constantly saying his back hurts and legs hurt so saw doc and got refered to hospital ... they have said he has got (tight gastrocnemei & hamstring aswell as tenderness in lower lumbar sacral spine) that is copied off the exact letter received from hospital !!! they are giving him physio starting next wk and we go back to see the specialist in 6 month .. but i have tried lookin on net to see exactly what all this means and cant find anything so would be gratefull if anyone could tell me any good sites or personal experience of the problem i just really want to no what to expect of happening ... thankyou in advance to anyone who answers ..