Sorry to be a pain about this, but in your reply you mentioned the L4/5 disc twice.
On the disc with the herniation, does it say that the disc protrudes 9mm into the canal or that the canal is narrowed to 9 mm?
Is the leg pain constant and where is it located?
What kind of doctor have you seen? Any treatment so far?
If in fact the disc is protruding into the canal by 9 mm, that is a large herniation. Fortunately, you have not indicated that your pain is that severe, so that is a good sign.
Also, the transitional segment could potentially affect normal lumbar spine mechanics. A transitional segment is a congenital condition.
If you are interested in learning about the low back and how to prevent injury and develop a RH program, then you should get the Ultimate Back Fitness and Performance book by Stuart McGill.