Understanding Sciatica: The Connection Between Leg Pain and Back Pain

Sciatica is a common condition characterised by pain radiating from the lower back down to one or both legs.  It occurs when the sciatic nerve or lumbar (lower back) nerves, the longest nerve in the human body becomes compressed or irritated. The sciatic nerve originates from the lower lumbar nerves (lumbar 4 and lumbar 5) and the sciatic 1 nerves. It runs from the lower spine, down the buttock, back of thigh and calf to the feet.

Sciatic pain is in the distribution of the sciatic nerve (lower back, buttock, back of thigh and calf). This can cause debilitating pain, loss of mobility and function. In severe cases, there can even be weakness of ankle dorsiflexion or big toe strength depending on which component of the sciatic neve is compressed.

There are several causes that can lead to sciatic nerve compression. The most common is a herniated disc which occurs when the soft inner material (nucleus pulposus) of the spinal disc protrudes and compresses the sciatic nerve. This can result in constant pain down the leg even when sitting or resting.

Another is spinal stenosis which occurs in middle age or elderly patients when the spinal canal narrows due to facet joint arthropathy, ligamentum flavum thickening, and disc bulging which compresses the nerves. This can cause neurogenic claudication in which there is leg pain on walking or standing for a short period of time and relieved on sitting to rest.

Less common causes are piriformis syndrome (piriformis muscle in the buttock compresses the sciatic nerve), pelvic fractures, or tumours in the pelvic region.

If you have sciatica or neurogenic claudication (leg pain on walking a certain distance), an MRI lumbar spine scan is recommended if the pain is persistent despite rest and analgesia. The MRI scan will show if there is any nerve compression. Most times, the symptoms will resolve with a course of anti-inflammatories, neuropathic pain killers (e.g. Gabapentin, Pregabalin) and physiotherapy. Occasionally, steroid nerve root injections or epidural steroids can be given for short term relief of the pain.

In severe cases, a decompression surgery might be needed which can be done via a mini-open or endoscopic approach with minimal downtime for recovery and longer lasting relief of pain. In summary, back pain and sciatica will usually get better with rest and a short course of analgesia and physiotherapy. If it does not, consulting spine specialist Dr. Gamaliel Tan is recommended.