Sciatica: The medical definition of sciatica is any sort of pain caused by irritation or compression of the sciatic nerve. It is important to understand that sciatica itself is not a diagnosis but actually a symptom. The sciatic nerve is the longest and widest nerve in the human body and originates from the lumbosacral plexus L4-S3 ( the lower back). The nerve passes through the piriformis muscle at the buttock region and down the lower limb.
Soft tissue irritation around the lumber facets
Disc herniation (see below)
Lumber facet joint irritation/inflammation
An individual’s mechanism of injury should give strong evidence to which of the above is the primary cause of sciatica, though often sciatica is caused by a combination of the above.
Soft tissue irritation:
macrotraumatic injury - a specific incident injury such as trauma or a 'pull'/ strain of the lower back with a heavy lift.
microtraumatic injury - repetitive 'small' injuries wherby the rate of injury surpasses the rate of tissue healing, examples include repetitive lifting with poor technique. Another example of a microtramitic injury includes abnormailities in an individuals biomechanics*
Around the age of 19 degeneration begins to take place and therefore we would expect that any average individual at the age of 35 for example to show disk degeneration and disc bulges (protrusion) if the lumber spine was to undergo MRI.
Disc extrusion and sequestration are predominantly caused by a specific incident of injury.
Disc extrusion: when the outer spine of the disc ruptures which allows the inner, gelatinous part of the disc to squeeze out, this can occur with the ligaments intact or damaged.
A disc sequestration may require surgery in the form of spinal decompression or a discectomy (removal of all or part of the disc), surgery may also be offered to those who suffer with persistent and re-occurring disk problems. Though surgery is not without its risks and conservative therapy is preferred in the majority of cases. Discs can heal over time but the exact time frame is dependent on a variety of factors including the severity and position of the tear as well as individuals lifestyle factors.
Piriformis irritation/ inflammation (piriformis syndrome)
The piriformis is a muscle in the gluteal region of the lower limb. The sciatic nerve directly passes through the piriformis muscle in around 20% of the population. When the piriformis muscle shortens or spasms due to trauma or overuse, it can compress or strangle the sciatic nerve. Typical causes are overuse of the muscle through activities adopting the sitting position such as rowing or cycling, biomechanical abnormalities through over pronation ( see ‘importance of biomechanics’) or stiffness and hypomobility of the sacroiliac joint ( the joint that meets the pelvis and lower back).
Facet joint disorders
Facet joints help the spine to bend, twist, and extend in different directions. Although these joints enable movement, they also restrict excessive movement. Although not a common cause of back pain sudden movement that traumatises the facet joint will cause pain and localised inflammation and irritation which can irritate the sciatic nerve. It is not uncommon for an individual to experience a sudden ‘click’ at the lower back when this occurs.
Long term facet joint disorders are generally down to degenerative and arthritic changes in the joint. An individual with arthritic changes in the joint is likely to experience ‘flare ups’ which not only cause pain but also secondary soft tissue irritation and inflammation around the joint which may irritate the sciatic nerve.
Spinal manipulations are key in the treatment of facet joint disorders as they ‘open’ up the joint and re nourish the synovial fluid , this helps release nerve compression and reduce secondary irritation.
Other causes of sciatica include underlying pathologies such as:
Various diseases of the bone
In addition to the gradual wear and tear that comes with ageing, other factors can increase the likelihood of a herniated disc and other degenerative changes of the vertebrae.
BMI: those who are overweight are more likely to suffer from degenerative changes due to the amount of stress that is put on the lower back
Sedentary lifestyle: regular exercise will have many advantages including improving your tissue quality, strengthening your lower back and reducing the chances of other medical conditions that may effect healing rates such as diabetes.
Repetitive and/or Improper lifting: using poor techniques to lift will put added strain on your lower back, twisting while lifting makes the back particularly vulnerable in obtaining an injury. Putting more emphasis on lifting with your legs will reduce the strain on the back.
Long periods of sitting: Those individuals with driving or office based occupations are more at risk of degenerative changes due to inactivity and continued stress on the back.
Smoking. It is believed that smoking lessens oxygen supply to the disc and causes more rapid degeneration.
Generic physiotherapy treatment protocol:
manaul therapy into the soft tissues of the lumber spine and the piriformis muscle with trigger point therapy
manipulate the lumber spine .
Asses biomechanics if relevant and orthotics.
Lower back strengthening programme when relevant.
If activity provoked – rest is essential.
If a disc is indicative then do not manipulate the spine however continue to use deep soft tissue techniques and advise icing only
Severe degeneration and spinal stenosis cannot be treated with physiotherapy alone and may require surgery or injection if appropriate.
* please see 'importance of biomechanics' for more information