In many cases of sciatica there is no single obvious cause. It is thought that general 'wear and tear' on the body may lead to episodes of sciatica. This is why the condition is more common in people who are over 40 years of age or those who have occupations that involve a lot of physical activity.
Some other potential causes of sciatica are outlined below.
Herniated disc
A herniated (or slipped) disc is the most common identified cause of sciatica.
Your spine is made up of vertebrae, discs, and nerves. Vertebrae are the ridge-shaped sections of bone that make up the structure of your spine, and protect the nerves. The vertebrae are supported and cushioned by discs of cartilage. Cartilage is a type of tissue that is tough and flexible.
As a person gets older the discs start to become harder, tougher and more brittle. Repeated strain on the back means that there is a chance that the hardened discs may split or rupture. If a rupture occurs some of the soft core of tissue inside the disc can press against the sciatic nerve, causing sciatica.
Spinal stenosis
Spinal stenosis is caused by a narrowing of the spinal cord - the long tube inside the spine which contains the nerves. As you get older, the spinal cord can narrow. If the narrowing occurs in your lower back, the sciatic nerve may be compressed, leading to sciatica.
Spondylolisthesis
Spondylolisthesis is a condition where the discs degenerate to such an extent that they are no longer able to properly support the vertebrae. This may lead to a vertebra slipping forward over the one below it. If this occurs in the lower back, the slipped vertebra can compress the sciatic nerve, causing sciatic pain.
Other causes
Less commonly, sciatica may be caused by infection, injury or a growth within the spine.
