Sciatic pain is often caused by a trapped nerve from a bulging disc (also called slipped disc, prolapsed disc and herniated disc in varying degrees of severity). The lowest discs in the spine are the most vulnerable as they are carrying the most weight. In addition to this, the transition between the highly mobile lumbar spine and the immobile pelvis puts more mechanical stress at this level.
In sciatica problems, the numbness and weakness, may often be worse than the pain. If nerves, like the sciatic nerve, that come out of the spine get trapped, the first thing to happen is pain as the nerve itself gets inflamed. If the compression on the nerve continues then you experience tingling, pins and needles and eventually numbness and paralysed muscles in the leg.
Interestingly you may not even have a sore back. If the compression is not relieved urgently, this can cause permanent problems. Often, however, sciatica and disc bulges are misdiagnosed.
A recent review on all forms of manual therapy found that there is moderately positive evidence that manipulation is helpful for sciatica. The most important thing for a quick and complete recovery is to stay as active as you can manage and to do the exercises that are prescribed. These may include sit-ups and back extensions over a gym ball. This type of exercise strengthens the core stability trunk muscles and the small muscles in between the vertebrae themselves. This reduces the mechanical strain on the discs and joints and not only helps with recovery but also preventing it happen again.