From health.com
The sciatic nerve is the body’s largest and longest nerve, running from the lower back down through the back of each leg. This nerve stimulates leg muscle movement and carries sensory signals from the legs to the spine, helping you complete daily functions like walking and standing. Irritation of or damage to the sciatic nerve can lead to multiple health conditions, causing pain, numbness, tingling, and more.
Anatomy of the Sciatic Nerve
The sciatic nerve is a part of your peripheral nervous system, which is made up of the nerves that exist in your body but are located outside the brain and spinal cord.
Structure
The sciatic nerve is formed by nerve roots that branch out from the lower lumbar (lower back) and upper sacral (low spinal area) spine. This nerve is considered a mixed nerve and consists of a bundle of both motor and sensory nerve fibres. This bundle is surrounded by a layer of connective tissue known as the perineurium.
Location
Starting at the base of the spine, the sciatic nerve travels downward through the buttocks and along the back of the entire leg. As it extends down the thighs, the sciatic nerve gets slightly wider and then splits into two branches around the knee area. Smaller sciatic nerve branches are also clustered around the hip, inner thigh, lower legs, and feet.
At these locations, the sciatic nerve fibres supply the lower body region with nerve impulses, controlling muscles and sensations throughout parts of the lower back, legs, ankles, and even into the feet.
Anatomical Variations
The exact placement of the sciatic nerve in the pelvis can vary from person to person. Research suggests that roughly 16% of people may have different variations in the anatomy and pathway of the sciatic nerve.
While the most common placement of the sciatic nerve is extending down underneath the piriformis muscle (located near the pelvic region and hips), other variations involve the sciatic nerve dividing above the piriformis muscle before merging again. These variations are still considered normal, but they may make it more likely to develop sciatica pain.
What Does the Sciatic Nerve Do?
The sciatic nerve is a type of somatic nerve that goes into the skin and muscles and is involved in conscious, functional activities, such as lower body leg movement and sensation.
The two most common functions of the sciatic nerve include:
- Motor function: Sends signals from the brain that supply the muscles in the leg, back of the knee, and lower leg with movement
- Sensory function: Picks up signals that provide sensation and feeling to the back of the thigh, part of the lower leg, and the sole of the foot
Associated Conditions
When the sciatic nerve becomes damaged, injured, irritated, compressed, or inflamed, you can develop sciatic nerve pain. Several conditions can cause this pain to occur.
Sciatic Nerve Injury
An injury directly to the sciatic nerve can happen when you experience physical trauma like stretching, cutting, or intense pressure directly to the nerve. These injuries are most likely to occur during surgery, such as a total hip replacement. They could also result from an infection injury after getting an intramuscular injection in the lower body, like the glutes.
If you develop a sciatic injury, you may experience the following symptoms in your glutes and legs:
- Pain
- Loss of muscle movement
- Lack of sensation
- Abnormal ankle reflexes
- Difficulty bending the knee or the foot in certain positions
Herniated Disc
A herniated disc (or a slipped disc) often causes increased pressure on the sciatic nerve. It occurs when the round and flat pieces of cartilage between the bones of the lower spine slide out of position.
This sciatic nerve irritation or compression can lead to sciatica (sciatic nerve pain), which can come with the following symptoms:
- Sharp pain, tingling, or numbness that radiates from the butt to the leg
- Pain that worsens when standing, walking, sitting, or straightening the affected leg
- Lower back pain
Herniated discs commonly happen with activities like lifting heavy objects, sitting or standing for long periods of time, and aging, as the spinal discs tend to degenerate or break down as you get older.
Spondylolisthesis
Spondylolisthesis is a condition that occurs when a vertebra (bone) in the spine slips out of alignment. If this happens in the lumbar region, it can actually pinch the sciatic nerve. This condition often occurs due to a spinal injury or natural wear and tear on the spine.
With spondylolisthesis, you may develop symptoms like:
- Pain, tingling, or numbness that starts in the lower back and spreads down the back of the leg
- Lower back pain
- Tight hamstrings
Piriformis Syndrome
The piriformis muscle, which runs from the lower back through the butt and down the top of the legs, is adjacent to the sciatic nerve. When the piriformis muscle directly presses on the sciatic nerve, it can cause piriformis syndrome.
This condition can affect the pelvic and gluteal regions and cause symptoms such as:
- Pain
- Tingling or numbness
- Loss of range of motion in the hips
- Difficulty climbing stairs
Generally, inflammation or injury to this muscle can compress the sciatic nerve. Athletes and people who perform repetitive hip and leg motions may be more likely to develop piriformis syndrome.
Spinal Stenosis
When the spinal column narrows and causes pressure on the spinal cord, spinal stenosis can occur. If this narrowing occurs in areas near the sciatic nerve, you may experience irritation and other symptoms that affect your butt and legs. These symptoms are most common with spinal stenosis:
- Pain that worsens when your legs are lifted straight in the air while lying down
- Numbness or tingling
- Muscle weakness
Spinal stenosis is more common with age, but it can also occur as a result of issues like congenital disorders that affect your spine at birth, spinal tumours, injury, or certain bone diseases.
Diagnostic Testing
If you're experiencing sciatic nerve pain, seeing a healthcare provider can help you get a proper diagnosis. To diagnose conditions related to the sciatic nerve, your primary care provider will often refer you to an orthopaedist (a doctor who specializes in bones and nerves). During your appointment with an orthopaedist, you can expect them to ask about your medical history and conduct or order the following tests:
- Physical exam: Various physical tests can help narrow down and assess any damage to the sciatic nerve. These involve testing the reflexes, the ability of joints to make certain movements, and sensitivity to cold, heat, and pain.
- Imaging scans: Taking X-rays, computerized tomography (CT) scans, or magnetic resonance imaging (MRI) scans of the lower back and pelvic area can screen for concerns with the vertebrae and sciatic nerve.
- Nerve conduction studies: Electromyography (EMG) and nerve conduction studies test the functionality of the sciatic nerve by checking the electrical signals between the sciatic nerve and its corresponding muscles.
Tips for Keeping Your Sciatic Nerve Healthy
A combination of lifestyle habits and activities can help keep your sciatic nerve healthy and reduce the risk of injury or inflammation. Consider the following strategies:
- Stay active during the day and avoid extended periods of rest if possible
- Engage in a regular exercise routine that focuses on strengthening your core, lower back, and pelvic muscles
- Support your spine with postural adjustments, such as keeping your back straight against a chair while sitting or using a lumbar support pillow
A Quick Review
The sciatic nerve is the largest nerve in the body, which runs from the lower back through the buttocks and down the back of each leg. This nerve plays an important role in helping your legs move and feel sensations, which allow you to stand, walk, run, and more.
Damage or injury to the sciatic nerve can cause pain, numbness, or weakness in your lower body. Staying active and using lumbar support can keep your sciatic nerve healthy in the long run.
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