I do not know which spinal disc you are asking about, I have spinal stenosis that went undetected until my leg collapsed while walking. Basically each spinal bone is separated by flexible discs allowing for flexibility of motion and room for your nerves that control various parts of body to perform without pain. An impinged nerve is one that will not work properly and can cause excruciating pain or lack of function. I hope this is helpful.
In someone who is getting older, these are all signs of wear and tear and indicate arthritis. Spinal stenosis can be congenital and doesn't leave much room for the nerves to pass through the spinal canal causing numbness and tingling in your legs