I recently started to gain back extreme pain in my lower back that does come sometimes a the worse times out of nowhere. its very severe sometimes and buckles me down to one knee when it radiates down through one of my legs? what is wrong?

Don't know but ...: If the pain that you have starts in your lower back and radiates down thru your buttocks and down the back of your leg you are describing the classic pain pattern of sciatica or slipped disc or pinched nerve. You and 40 million other Americans suffer from it. Most will get better with bed rest . Mild analgesics help too. Speak to your doc and try to avoid the surgeons scalpel.

Sciatica: This sounds like "sciatica" or a back problem pinching a nerve that runs down your leg. Most of the nerves send info up your spine and to the brain for further info. It does not matter where the nerve is injured, where it is supposed to go is where the pain is felt. If one of the nerves for you leg gets hurt in the back you feel pain in the leg. You likely have a back prob w a radiculopathy

The nerve: One of the lumbar nerve roots is being pressed upon or entrapped by whatever the cause of the back pain is and that could be one of the following: Vertebral disc herniation or bulge, spinal stenosis, severe arthritis, Myofascial dysfunction, muscular spasm, and a few others.