What is Sciatica?

Figure 1

Sciatica is lower back, buttock and leg pain, pins and needles and/or weakness indicating that the sciatic nerve is irritated.  It can be severe, lacerating pain, a constant nagging ache, or sometimes it can be like a jolting or electric pain.  The distribution of the pain is from the buttock down the back of the thigh, into the calf and sometimes all the way to the sole of the foot.

Sciatica is a neuropathic (sickness in the nerve) or neurogenic (coming from the nerve) pain.  This means it can be very difficult or impossible as a sufferer to localise the pain precisely to a single point; it just hurts across the entire area.  Sometimes the pain can be localised and this can be very instructive, however the variability of the nervous system between individuals means that even then it is necessary to draw cautious conclusions.

Sciatica is a very common complaint, but it is not a diagnosis.  To discover that the sciatic nerve is irritated does not tell you where along its path it is irritated or what is causing the irritation.  Often an intervertebral disc lesion, a bulge or even a rupture (colloquially known as a slipped disc) may give radiating pain into the posterior (back of the) leg.  A slippage of one vertebra on another (spondylolisthesis) can place pressure on the nerve within the spinal canal.  Zygapophyseal (spinal)  joint or sacroilial joint dysfunction can also give radiating pain.  The piriformis muscle that lies over (or in some people is penetrated by) the sciatic nerve can become chronically hypertonic (constantly spasm) and the pressure that puts on the nerve can give pain radiating in the sciatic nerve distribution (see Figure 1).  Knowing that the sciatic nerve is irritated is only the beginning of understanding how to resolve the problem.

All of the above could be clinically described as sciatic pain.  There are a number of other conditions that give very similar signs and symptoms to sciatica, but are not caused by the irritation of the sciatic nerve.  For example, myofascial trigger points in muscles both above and below the pelvis can refer pain into other muscles in the posterior leg and this can be just as painful.  Piriformis enthesopathy can have consequent spasms that seem identical to sciatica.  Posterior lower limb pain is therefore not necessarily sciatica.

Once an hypothesis of sciatic nerve irritation has been established, an Osteopath seeks to understand the source or sources of the pain.  Often the dysfunction has numerous layers, and resolving a (for example) muscle spasm will reveal a pattern of myofascial trigger points or local inflammatory swelling (oedema).  Often the prognosis will develop as more is discovered with treatment.  In some cases, particularly when the patient has lost sensation in parts of the sciatic nerve distribution, the Osteopath will refer back to a doctor for an orthopaedic surgical consultation.

For a very detailed discussion of sciatica, Chirogeek gives a great read.

For the Cochrane Review on spinal surgery for disc prolapse and its long term effectiveness.