My thought would be a facet problem in the lower spine, but since you have had all the tests without finding problems, then I suggest you look to your foot. If you stand or walk on the outside of the foot, that may be your problem. Walking on the outside of the foot forces the foot to turn inward and upward, throwing the spine out of alignment. This will cause pain in the front muscles of the thigh. Walking and exercise make the pain worse. Look at your shoes. How do they wear? Is the outside of the heel more worn than the inside? If it is, then this may be your problem. See an orthopedist that specializes in feet test you for balance and spinal alignment. You can get a special insert to fit into your shoes that will straighten the foot so you are again walking flat footed. This adjustment will straighten the spine, pelvis, and leg. The muscles of the thigh will ease and the pain will go away. Since you have had this problem for a while, the bones and muscles won't want to go back without a little complaint, so you may still have pain (a different pain) while the body adjusts to the re-alignment. good luck
The outside does not seem more worn than the inside. Any other suggestions of this?
Ever get checked for fibromyalgia?I have it and it makes different muscles sore all over my body for long periods of time.Its hard to diagnosed sometimes, but i found out i had it.My hip, back, forearms, and legs all have it..not always in the same spot every time, but my thighs get very uncomfortable.I wonder if you have it?You can see a rheumatologist for this.They will do some blood work and touch you in certain areas.