Sciatica is caused by injury or compression of the sciatic nerve, which is the longest nerve of your body. This nerve travels from the lower end of the spine crossing through the buttocks and extending down the back of the legs.
Sciatica causes a throbbing pain or a shock-like pain in your lower back. It usually radiates in one leg. In extreme cases, you may also feel leg weakness and numbness.
Disc herniation or disc slip occurs when one of the discs cushioning your vertebrae is compressed and protrudes outward, leading to disc rupture. When the protruded disc puts compression on nerves, it causes pain.
An injury may also lead to disc herniation. Its chances increase as you get older. Disc herniation mostly occurs in the lower back, but it may occur in your neck.