Updated: Feb 4, 2021
Sciatica Is the largest nerve in the body and very integral part of lower back, hips and legs. It's created by inflammation of the sciatic nerve, can affect one side of the body with various intensity of radiating & electrical pain, because of its location and combination of nerves( L4-S3) it is sometimes associated with back pain. The pain is characteristical of shooting type, quickly travelling along the course of the nerve.
Today I'll be talking about 3 main causes of Sciatica, but before that let's have a quick look at the anatomy of the Spinal column, more specifically intervertebral discs. Intervertebral discs sit between adjacent vertebrae and they're made up of fibrocartilage, this help to distribute pressure evenly across the discs, as well as to help provide movement between two vertebrae, there are 23 of them in the vertebral column, they get larger the lower they are in the spine. Discs are composed of 2 parts:
ANNULUS FIBROSUS: Which surrounds the inner gel-like centre & it seals the nucleus pulposus it's made up of water 60-70% and densely packed collagen lamellae (Bogduk 1997).
NUCLEUS PULPOSUS: Consist of several layers of fibrocartilage & lose collagen The nucleus of the disc acts as a shock absorber, absorbing the impact of the body's activities and keeping the two vertebrae separated.
So, how does it work? The nucleus Pulposus assists the annulus in resisting loads and supporting the spine by way of the fluid matrix within. In a healthy disc, this fluid ball in the middle of the disc is resistant to compression. When force/compression is applied to the disc the nucleus will flatten out and push against the annulus. This in turn causes stiffening of the annulus making it more rigid and resistant to force. When the load is released the annulus will recoil and cause the nucleus to restore its ball-like shape and return the disc to a normal state( Bogduk 1997).
What are the main causes of Sciatica:
1-DISC INJURY: External forces placed on the disc causes it to deform, general scenario is when nucleus Pulposus begins to migrate out of it centre-core posteriorly due to destruction of the rings of the Annulus Fibrosus creating a bulging disc, in more serious cases the disc may prolapse resulting in a partial/complete release of the Nucleus Pulposus, In this scenario, the nerve root is exposed to mechanical pressure created by the disc prolapse. L5-S1 intervertebral disc is most commonly affected by this injury where the pressure on the S1 nerve root relating to sciatica and lower back pain. 2-LUMBAR SPINE STENOSIS: With increasing, age discs undergo degenerative change similar to that seen in degenerative disc disease. Water is lost from the fluid matrix causing the disc to become less gel-like and more fibrous, which leads to micro-cracks and fissures within the disc, a history of injury to the spine as well as other occupational and physical characteristics may predispose someone for this condition. Symptoms tend to be related to extension movement of the lumbar spine or activities like prolonged walking or standing and it's relieved by bending forward. 3-PIRIFORMIS SYNDROME: When the piriformis muscle shortens or spasms due to trauma or overuse, it can compress or strangle the sciatic nerve beneath the muscle. Generally, conditions of this type are referred to as nerve entrapment or as entrapment neuropathies, the particular condition known as piriformis syndrome refers to sciatica symptoms not originating from spinal roots and/or spinal disc compression but involving the overlying piriformis muscle. Inactive glutes muscles also facilitate the development of the syndrome. These are important in both hip extension and in aiding the piriformis in external rotation of the femur. A major cause for inactive glutes is unwanted reciprocal inhibition from overactive hip flexors(psoas major, illiacus and rectus femoris). This imbalance usually occurs where the hip flexors have been trained to be too short and tight, such as when someone sits with hips flexed, as in sitting all day at work. This deprives the gluteals of activation, and the synergists to the gluteals (hamstrings, adductor Magnus and piriformis) then have to perform extra roles they have not evolved to do. Resulting hypertrophy of the piriformis then produces the typical symptoms. Overuse injury resulting in piriformis syndrome can result from activities performed in the sitting position that involves strenuous use of the legs as in rowing, sculling and cycling Runners, cyclists and other athletes engaging in forward-moving activities are particularly susceptible to developing piriformis syndrome if they do not engage in lateral stretching and strengthening exercises. When not balanced by lateral movement of the legs, repeated forward movements can lead to disproportionately weak hip abductors and tight adductors. Thus, disproportionately weak hip abductors/gluteus medius muscles, combined with very tight adductor muscles, can cause the piriformis muscle to shorten and severely contract. Upon a 40% increase in piriformis size, sciatic nerve impingement is inevitable. This means the abductors on the outside cannot work properly and strain is put on the Piriformis. The result of the piriformis muscle spasm can be impingement of not only the sciatic nerve but also the pudendal nerve. The pudendal nerve controls the muscles of the bowels and bladder. Symptoms of pudendal nerve entrapment include tingling and numbness in the groin and saddle areas and can lead to urinary and faecal incontinence. When piriformis syndrome is caused by weak abductors combined with tight adductors, highly effective and easy treatment includes stretching and strengthening these muscle groups. An exercise regimen targeting the gluteus medius and hip abductor muscle groups can alleviate symptoms of piriformis syndrome within days. Another cause for piriformis syndrome is stiffness, or hypomobility, of the sacroiliac joints. The resulting compensatory changes in gait would then result in shearing of one of the origins of the piriformis, and possibly some of the gluteal muscles as well, resulting not only in piriformis malfunction but in other low back pain syndromes as well. Piriformis syndrome can also be caused by overpronation of the foot. When a foot overpronates it causes the knee to turn medially, causing the piriformis to activate to prevent over-rotating the knee. This causes the piriformis to become overused and therefore tight, eventually leading to piriformis syndrome. (Wikipedia)