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  1. What is the Sciatic Nerve?
  2. What are the symptoms of Sciatica?
  3. How does the sciatic nerve get injured?
  4. Disc bulge compressing on the sciatic nerve
  5. How do we treat disc bulges that cause Sciatica?
  6. How do we diagnose sciatic nerve injury?
  7. The role of rehabilitation in sciatica

1. What is the Sciatic Nerve?

The sciatic nerve supplies sensation (via dermatomes) to the back, buttocks, thigh and foot, and supplies power (via myotomes) to the hamstrings, calf, ankle and foot. Please see the LBSM guide on Peripheral Nerve Injury and Entrapment to learn more about spinal nerves, dermatomes and myotomes.

sciatic nerve

2. What are the symptoms of Sciatica?

When the sciatica nerve gets injured or inflamed, it causes Sciatica. As with any peripheral nerve injury, sciatica may have sensory or motor symptoms. Please see the LBSM guide on Peripheral Nerve Injury and Entrapment to learn more about sensory or motor symptoms.

Sensory symptoms

The sensory symptoms described below are usually experienced along the dermatomal distribution of the sciatic nerve and can be felt anywhere from the lower back to the sole of the foot.

  • PAIN. Pain symptoms can range from sharp to dull, persistent to intermittent, and remain in one location or radiate to other parts of the body
  • NUMBNESS. This may present as a partial or complete loss of feeling or touch sensation
  • PARAESTHESIA. This essentially means “pins and needles” and can be associated with numbness
  • LOSS OF PROPRIOCEPTION. Ankle balance can sometimes be affected with sciatica.

Motor symptoms

The motor symptoms described below are usually experienced along the myotomal distribution of the sciatic nerve and can occur anywhere from the lower back to the toes. With more chronic sciatica, weakness may be very subtle and take weeks or months to become apparent. Wasted muscles are often lacking in strength but usually can be built up again.

  • WEAKNESS. The most common motor sign in sciatica is a reduction in power in the gluteal, hamstring and calf muscles. With acute sciatica, weakness can come on quite quickly. With more chronic sciatica weakness may be very subtle and take weeks or months to become apparent.
  • MUSCLE WASTING. The muscles that are supplied by an injured nerve may become smaller in size or completely wasted over time. In sciatica, this includes the gluteals, hamstrings and calf muscles. Wasted muscles are often lacking in strength but usually can be rebuilt.
  • HYPOTONIA. The tone (ability to contract) of muscles can also be affected from sciatic nerve injury. This may leave muscles flaccid, floppy and unable to produce forceful contraction.
  • SLOW REFLEXES. Motor nerves are also responsible for providing muscles with their reflex responses. Reflexes can become slower and more sluggish after nerve injury. This can be tested in clinic with a tendon hammer.


3. How does the sciatic nerve get injured?

There are many ways in which the sciatic nerve can be injured (please see LBSM Peripheral Nerve Injury and Entrapment guide) but by far the most common is through nerve entrapment. Below is a summary table of the causes of sciatic nerve entrapment with examples.

Masses compressing the sciaticSpinal disc herniation (aka disc bulge) Masses arising in the back and pelvis (e.g., fluid collections, soft tissue)
Prolonged compression of the sciatic nerveSedentary lifestyle Excessive sitting e.g., driving Poor workplace set up
As the sciatic nerve passes through muscle groupsLower back muscles (erector spinae, psoas), Gluteal, Piriformis, Pelvic floor, Hamstring
As the sciatic nerve passes through other structuresExiting foramen (holes) in the spinal column Spondylolisthesis (slipping of spinal vertebrae)

4. Disc bulge compressing on the sciatic nerve

What is spinal disc bulge?

The most common structure that compresses the sciatic nerve are spinal discs. Spinal discs provide the key functions of stability, movement and protection for the vertebral column and spinal cord. Each spinal disc lies between two spinal vertebrae. Each disc has a soft gelatinous centre (the nucleus pulposus) with a firmer harder casing (the annulus fibrosus), analogous to a Jam Donut. Just behind the disc lies the spinal cord, with spinal nerve roots exiting on both sides.

spinal disc bulge

Spinal discs are dynamic and mobile structures. They move in harmony with the rest of spine. When discs are forced into positions where there may be overstressed (e.g., forward, sidewards or backward bends) a disc bulge can occur. Discs may also become injured with less extreme movements, especially when muscles of the back are not primed and ready to support the discs (e.g., picking up an object incorrectly). Poor standing and seated postures as well as sedentary behaviours also increase the disc of getting disc bulges.

This picture shows a side view of the spine through an MRI scan. The orange blocks are the vertebral bodies with the purple ovals the discs in between them.


The green lines outline the spinal canal and cord. It is very normal for the discs in the lower part of the spine (especially the discs between the L4 and L5 vertebrae, and the L5 and S1 vertebrae) to be subjected to wear and tear, as this part of the spine has large amounts of force and load going through it.
The “jam” tends to become thicker and more viscous and is sometimes labelled as disc dehydration. Disc dehydration is a completely normal phenomena and occurs in almost everyone as we get old.


“Disc Bulge” is a generic term and refers to one of the following three types of mechanism of injury.

disc bulge


This can cause acute pain in the back at the level of the disc, but as the “jam does not leave the donut” there is often no surrounding nerve irritation or sciatica symptoms. This type of disc injury is called an Annular Tear.


There is still no spillage of jam out of the donut, but this time the annulus itself may contact and irritate the surrounding nerves roots. This type of disc bulge is called a Prolapsed disc and can often occur and recovery over a period of months to years.


Disc injuries that cause the “jam” to spill out of the donut are often acute and very painful and are called a Sequestrated disc. The nucleus, or “jam”, is highly irritative and can cause lots of inflammation around the nerve and its sheath. Fortunately, the body is very good at absorbing the “jam” so symptoms tend to settle fairly quickly, often with complete resolution.

In reality, it does not really matter which type of disc bulge you are suffering with as the treatments and rehabilitation strategies will be largely the same.

In some cases, understanding the nature of the disc bulge may give some insight around the length and duration of symptoms as well as influencing further treatment decisions.

new figure sciatica


5. How do we treat disc bulges that cause Sciatica?

Once a disc bulge has been diagnosed there are several treatment options.

  • NATURAL HEALING AND LIFESTYLE MODIFICATION. Most disc bulges will resolve themselves within 4-6 months if we manage them correctly. It is important to change various aspects of our lifestyles and improve the health of our spine. We can modify our activities, exercise, workplace set up and sleep patterns to create the optimum environment for healing.
  • REHABILITATION. The role of rehabilitation is outlined below and is a vital step when recovering from a disc bulge.
  • REDUCING THE INFLAMMATION AROUND THE NERVE. In acute disc injuries where there is lots of inflammation around the sciatic nerve roots, this treatment option can be very effective for reducing pain symptoms and aiding normal function. This can be achieved by anti-inflammatory medication or spinal injection therapy for short courses. These treatments are best given in conjunction with the steps outlined above.
  • REMOVING THE PART OR ALL THE DISC TO DECOMPRESS THE SCIATIC NERVE. – As mentioned above, the body has a great capability to self-correct disc bulges. However, sometimes removing the disc material and “creating more space” within the spine for nerves to transit is required. This may be the case when symptoms are severe (sensory and/or motor) and all other treatments have failed.

Other masses compressing on the sciatic nerve

Much less commonly, it is possible to have other masses in the back, pelvis and thigh that press on the sciatic nerve. In this case, symptoms can be much more sinister in nature (e. G. , weight loss, bloating, temperatures, change in bowel habit) and this usually prompts further medical investigation. Examples of such masses include collections of fluid, infections, soft tissue masses and cysts. Investigations such as an mri scan can rule this type of pathology out. If there is a mass compressing on the sciatic nerve, removing it medically or surgically usually improves symptoms.

Prolonged functional compression of the sciatic nerve

We may have experienced the sensation of sciatic nerve compression after slouching or sitting down for too long, particularly on a hard surface. This can cause pins and needles and weakness down the leg as well as buttock and lower back pain. Prolonged compression can eventually cause the sciatic nerve to become inflamed. Activities that leave us exposed to this included driving, poor workplace set up and sedentary lifestyle. If we can mobilise often, and keep the core, gluteal and thigh muscles active, we greatly reduce the risk of compressing the sciatic nerve.

Sciatic nerve entrapment from muscle groups

tension and weakness through certain muscle groups including the lower back muscles, gluteal, pelvic floor and hamstrings can trap the sciatic nerve and irritate it. These symptoms can often be misinterpreted as a muscle strain or injury (e. G. , pulled hamstring). By keeping these muscle groups active, strong and flexible, we can reduce the tension put on the nerve and improve any sciatica symptoms. Incorporating regular exercise and appropriate rehabilitation routines into our lifestyle is key.

Sciatic nerve entrapment from other structures

It is normal to have wear and tear in the bones and joints of spine. This can sometimes cause compression or irritation of the nerves as they leave the spine through there bony tunnels (foraminal stenosis). Examples of this may include arthritis of the spine, or slipping of the vertebrae (spondylolithesis). The joints that connect the vertebrae together (facet joints) can also be inflamed and cause sciatic nerve irritation.

6. How do we diagnose sciatic nerve injury?

Most of the time, sciatica is diagnosed clinically after discussing your symptoms and a thorough examination. Sometimes further investigation may be needed to confirm the diagnoses. These can be divided into investigations that (1) look at the spine, the sciatic nerve, its surrounding structures and its course (2) test the conduction and speed of the sciatic. Both these investigations may help to confirm the diagnosis and plan ongoing rehabilitation.

  1. An MRI scan is a key investigation which allows us to look at the spine, the sciatic nerve, its surrounding structures, and its course down the leg. This can help us identify anything that may be compressing the nerve or causes inflammation (e.g., disc bulge, pelvic mass). It may be possible to tell if the sciatic nerve is thickened or swollen, indicating injury.
  2. Nerve Conduction and EMG studies can measure how well the sciatic nerve is firing, conducting signal and whether there are any changes in muscle activation.

7. The role of rehabilitation in sciatica

Along with lifestyle modification, rehabilitation is the cornerstone in treatment for spinal disc injury and sciatica. The picture below shows a cross-sectional view of the lumbar spine taken from an MRI scan.

The yellow lines highlight the huge core and back muscles that envelope the spine to support and protect it. They have an intimate relationship with the vertebral column itself highlighted in orange (the vertebral body, spinous processes and facet joints).

In the centre of this complex is the spinal cord and the nerve roots leaving from either side.


  • REDUCE BACK MUSCLE SPASM. With any injury of the spine, the muscles of the back go into spasm to protect the spine. Although a completely natural response, this can be very painful and debilitating. The first step in the treatment of sciatica should be to improve the mobility and flexibility of the back muscles as quickly as possible, releasing them from spasm and getting them to function normally.
  • REDUCING SCIATIC NERVE TENSION AND TIGHTNESS. Exercises such as neural glides can improve the tension in the sciatic nerve and release the nerve from inflamed surrounding tissue and tight muscles
  • IMPROVING CORE, BACK, GLUTEAL AND HAMSTRING STRENGTH AND FLEXIBILITY. The longer-term goal in the rehabilitation of sciatica should be focused around improving the strength of the muscles that the sciatic nerve supplies, as well as the core and back muscle that support the spine.
  • MODIFY AGGRAVATING FACTORS. By being aware of factors that may put our spine and sciatic nerve into compromising positions, will help us avoid repeat flares.

It is important to discuss any potential signs and symptoms of sciatica with your doctor to get a clear diagnosis and treatment plan.

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    Orla Mulligan is the administration and social media manager for LBSM. She has a strong background in sport having herself played netball at an elite standard for the U21s Northern Ireland team in the European Championships as well as the U21s competition for Saracen Mavericks.

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    Mr Saha studied medicine at the United Medical & Dental Schools at Guy’s and St. Thomas’ Hospitals before completing his higher surgical training in London and the South East. During this time, he was awarded the prestigious NIHR Clinical Lectureship in Vascular Surgery at St. Thomas’ Hospital, giving him comprehensive training in open and endovascular techniques for treating arterial and venous disease. Prakash completed his aortic surgery training at the St. George’s Vascular Institute before carrying out a specialist fellowship at the Royal Prince Alfred Hospital, Sydney.

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