Legs tire easily - What could cause?

My legs, well actually my thighs, and arms will get very tired and "quit working".  At times I get a pinching feeling in the thighs as well.  With rest the muscles recover.  This does not happen consistently but rather comes and goes.  I have been to many doctors and they have not been able to tell me what's wrong.  I have had many blood tests, EMGs and even a muscle MRI.  They say all tests have been normal.  They usually say that my muscles are deconditioned and to exercise them.  This started about 10 years ago after I had surgery on my neck for a C4-5 disc problem.  My spinal cord was being severely compressed because of a ruptured disc (I was told by my surgeon that my spinal cord looked like a kidney bean).  The doctors admit that the arm tiredness could be a result of the problem in my neck due to pinched nerves.  However, they won't say the same about my legs.  So, my question is, is it not possible that, since it was my spinal cord that was being compressed, or pinched, by the disc, that the tiredness I get in my legs is a result of that?  I feel like everyone gets caught up in the notion of a pinched nerve occurring where the nerve exits the vertebra.  However, since the spinal cord is the big bundle of nerves, would it not be possible for the nerves that control the muscles of the leg to be pinched, even if the pinch occurs further up the spine?