A woman was injured several years ago in a car accident and she was diagnosed with a herniated disc. Can you please explain using the correct anatomical terminology what herniation of a disc means and where is it likely to occur in the vertebral column? In addition, she often feels pain in the posterior surface of the thigh radiating to the area behind the knee what major nerve do you think is being compressed and where is the likely region of the injury in the axial skeleton? (I need more help with figuring out which nerve is being compressed.)