The lumbosacral joint (L5-S1) is a joint in the spinal column between the last vertebra of the lumbar region and the first vertebra of the sacral region. At this point, there is a shift in the curvature of the vertebral column from a forward curvature in the lumbar region to a backward curvature in the sacral section of the spinal column.
This joint is particularly prone to many types of injuries such as disc herniation, degenerative changes in the disc, and various types of injuries due to its critical location in the spinal column. One of the functions of this joint is to shift weight from the spinal column to the pelvis. This weight-bearing function also makes it prone to high amounts of shear stress.
Common health issues at L5-S1 joint:
The most common issues that originate from the L5-S1 joint can take many forms such as bone-related problems, intervertebral disc disease, and nerve-related problems.
Intervertebral Disk related problems
The disc between the fifth lumbar and first sacral vertebrae has a steeper angle making it more prone to mechanical stress. Most disc abnormalities occur between the fifth lumbar vertebra and first sacral vertebra. These intervertebral disc-related problems can take many forms:
- Degenerative disk disease: Degeneration occurs when a disc has degenerated because of loss of fluid, wear and tear of a disc, or structural changes like thinning and breakdown of the disc.
- Bulging disk: This primarily occurs when the disc dries out and gets compressed between the fifth lumbar and first sacral vertebrae. The compression breaks down the outer ring of the disk allowing the inner part of the disk or nucleus pulposus to bulge out.
- Herniation of disk: When the mechanical stress on the spine increases to a degree, the inner part of the disk may rupture out of its outer part. The disc may get broken into pieces too. This condition is called herniated or ruptured disk.
L5-S1 joint-related problems
As the L5 and S1 vertebrae suffer excess amounts of stress due to their critical location and function, the joint may develop many abnormalities with increased age. Some of these abnormalities are mentioned below:
- Osteoarthritis: This is the wear and tear type of arthritis. It develops due to aging and because of the weight-bearing function of the lumbosacral joint.
- Stressed joint or fracture of the vertebra: Due to repetitive stress on the fifth lumbar vertebra, a small part attached to the joint between two facets can become stressed. And if this excess pressure continues, this segment can get fractured as well. If it is fractured, it is called spondylolysis.
- Spondylolisthesis: It develops when the fifth lumbar vertebra slides over the first sacral vertebra. It occurs when parts joining the two facets joints are fractured on both sides of the fifth lumbar vertebra.
Nerve related problems
Many nerve-related conditions can develop at the lumbosacral joint due to spinal nerve inflammation or secondary to joint or disc conditions. The nerve root compression can occur due to altered bone structure secondary to disease and it can produce various symptoms along the nerve route in the body. Common nerve conditions that develop between the fifth lumbar and first sacral vertebrae are:
- Sciatica: It occurs when nerve roots of the sciatic nerve become compressed between the fifth lumbar and first sacral vertebrae due to a bone or disc-related disease. It is also called lumbar radiculopathy.
- Cauda equina syndrome: It develops when nerves of the cauda equina have been damaged at the lumbosacral joint. Cauda equina nerves are a collection of lumbar, sacral, and coccygeal nerves that originate from lumbar enlargement of the spinal cord.
Most common symptoms at L5-S1
The symptoms that develop due to a condition between L5 and S1 vertebrae depend on the underlying pathology.
Joint or disc-related symptoms: Symptoms originating from vertebral conditions, vertebral joint conditions, and disc-related issues at L5-S1 are, localized lower back pain and difficulty while performing certain daily activities. This pain can be a lingering dull ache or a stabbing sharp pain that may worsen due to many movements and may get better when those movements are restricted. In particular, pain originating from disc disease may get worsened succeeding long hours of sitting or standing, or lifting heavy objects.
Nerve-related symptoms: Due to nerve inflammation or its compression, many symptoms can also occur. Usually, nerve pain manifests on one side of the body but it can manifest on both sides of the body.
- Pain: Pain originating from nerve inflammation or its compression is usually sharp shooting pain along the area of nerve supply. At L5-S1, this pain usually starts in the gluteal region and goes down towards the lower leg and feet.
- Weakness and numbness: Weakness and numbness usually occur in the foot or toes. One may not be able to lift the foot off the ground.
- Cauda equina syndrome: In this syndrome, there is pain in the genital or groin area, and loss of bladder and bowel control, may be present too.
How are L5-S1 issues diagnosed?
The doctor will take a detailed history of current health problems and past medical and surgical conditions, perform a thorough physical exam, and may order one or a few of the following tests to reach a diagnosis.
- X-ray: This test uses X-rays and can help diagnose bone and disc-related disease.
- CT scan: CT scan is also called computer tomography scan. It uses X-rays and a computer. The CT scan is more detailed than X-rays as it produces images from different angles of the tissues, and it shows bones, muscles, fat, and organs in detail. This test can help diagnose L5-S1 related conditions.
- MRI: It is also called a magnetic resonance imaging scan. It uses computers, large magnets, and radio frequencies to make detailed images of the different internal tissues and structures of the body.
- Myelogram: It is used to make the spinal canal visible on an X-Ray. A dye is injected into the spinal canal which is then visualized on an X-Ray film.
- EMG: Electromyography (EMG) is a test in which a nerve is stimulated and the consequent response in muscle is measured.
Options for treatment
There are many treatment options available for health conditions associated with L5-S1 dysfunction. In people who don’t have associated neurological symptoms, non-surgical options for treatment may be more suitable.
The doctor will choose a treatment option depending on the underlying health condition and associated symptoms.
The doctor may use one or many of the following treatment options.
Surgical options for L5-S1 treatment
A surgeon may perform one of the following surgical options or may do more than one surgery at a time.
- Foraminotomy: This surgery is indicated when there is compression of the spinal nerve at the intervertebral foramen. During this surgery, the bone segments are trimmed to make the intervertebral foramen wider that helps in decreasing the compression of the spinal nerve. The excess bone growth may be cut as well.
- Laminectomy: A posterior part of the vertebrae called the lamina is removed to increase space for the cauda equina.
- Microdiscectomy: In this surgery, a small section of the intervertebral disc is removed along with a portion of a bone to decrease the spinal nerve compression.
- Lumbar interbody fusion: During this surgery, the damaged disc between L5-S1 is removed and the two vertebrae are fixed together. Sometimes, interbody support is placed to increase the chances of a successful surgery and recovery.
Non-surgical options for L5-S1 dysfunction
- Pharmacological treatments: If the person is suffering from mild pain, many over-the-counter medications for pain relief may help. If the person has moderate to severe pain, prescription pain killer medications like tramadol, opioids, and corticosteroids may be recommended.
- Physical therapy: Specific techniques are used to decrease the pain associated with L5-S1 issues. These therapies help stabilize the joint, increase the stability of muscles and heal the tissues in the back.
- Personal care: The doctor may also recommend improving personal care like adequate resting and daily physical activity and also, using ice at home for pain relief.
There are also many injection treatments in which many medications like corticosteroids are injected into the epidural space in the spinal cord and these decrease sensitivity of nerve fibers to inflammation and irritation.
- Spine-health, All about L5-S1 (Lumbosacral joint), Accessed March 31, 2021, https://www.spine-health.com/conditions/spine-anatomy/all-about-l5-s1-lumbosacral-joint
- Hopkins medicine, Lumbar Disk Disease, Accessed March 31, 2021, https://www.hopkinsmedicine.org/health/conditions-and-diseases/lumbar-disc-disease-herniated-disc
- Precision Brain, Spine, and Pain, Sciatica, Accessed March 31, 2021, https://www.precisionhealth.com.au/healthcare-services/pain-management/conditions-treated/spinal-conditions/sciatica/