I have been going to the gym for the last 5 months and have lost 7 kilo's. I recently started running on the treadmill (about a month ago), and now I have pain in my legs. The pain is so bad at times that I can't even walk up or down stairs. It is like a stabbing pain which runs right up the middle of my leg, and it is affecting my knee and hip joints. I have been to 2 pediotrists, and one said I have shin splints, and the other said I have tight calf muscles. I have done what they have told me to do (various stretches and warm ups) and have bought a new pair of runners. But I am still getting the pain. Does anyone have any suggestions?

You have it a little backwards. The hip and knee joint is affected first, and then impacts on muscles, ligaments and tendons taking the brunt and trying to keep up with the trauma done to the joints. Not unusual. You probably had a little arthritis in there. Concentrate on getting your joints back in shape. I suggest glucosomine/controindtin supplement which gets the joints more lubrication again. It isn't an instant fix but it will help. You could try wrap on your knee while working out to take the strain off.

If it is a touch of arthritis (join the club of many) then all you can do is take an anti inflammatory over the counter med like advil, motrin. You will find the one that suits you best.

Mind you I am not disputing the doctors.
Tick

Sorry to bring up the obvious, but are you drinking tons of water?
Next might be to try an OTC leg cramp medicine that contains quinine. It won't hurt to try it.