If I could ID the specific muscle or muscle group that has atrophied and I did progressive exercises to that muscle, wouldn't it improve over time? Would it improve even if the nerve in the lower back related to this muscle is still pinched a little?

The atrophy of the right leg starts immediately to the left (inside) of the knee cap and extends up the thigh about 6 or 7 inches. This inside muscle "sags" relative to that same area on the left leg. Due to this atrophy, the knee cap is very prominent relative to the left knee cap. If you know which muscle this is, what would be the best exercise to work this muscle? Is this the vastus medialis? The sartorius? Or what?

Jim