WHAT IS A DISC?
The spine has three main sections: Cervical (neck), thoracic (mid-back), and lumbar (lower back). The letter L - refers to lumbar. A spinal disc separates each vertebral body from the other.
A L4-L5 disc, refers to the disc that is in between the L4 and L5 vertebral body.
The disc absorbs compression within the spine - like a shock absorber
The disc provides flexibility
The disc protects from excessive motion
The spinal nerves pass right behind the discs