Many people suffer from what’s commonly known as sciatica, but understanding what causes sciatica matters more than the label itself, because it is more of a symptom than a diagnosis.
Sciatica describes a pattern of indications, most commonly pain that travels from the lower back, buttock, or hip and into the leg. The term may tell us where you hurt, but not necessarily why you hurt. That distinction matters, as the why is what tells us how to help.
The sciatic nerve is the largest and longest nerve in the human body. It originates from the nerve roots in the lower spine, travels through the pelvis and buttock, and continues down the back of the leg before branching into smaller nerves that extend into the lower leg and foot.
Along that pathway, there are multiple places where the nerve or nerve roots that form it can become irritated, compressed, or entrapped. A herniated disc is one possibility, but it is far from the only one.
Successfully treating sciatica starts with answering a more important question: what is actually causing the sciatic nerve to hurt?
What Is Sciatica?
Sciatica generally refers to pain associated with irritation of the sciatic nerve or the spinal nerve roots that contribute to it. Symptoms can include:
- Lower back or buttock pain
- Pain traveling down the back or side of the leg
- Burning or electric sensations
- Numbness or tingling
- Leg or foot weakness
- Pain aggravated by sitting, bending, walking, or certain movements
Two people can experience nearly identical “sciatica” symptoms while having completely different underlying problems. That is why treating the symptom alone can sometimes lead to months or even years of unsuccessful care.
What Causes Sciatica?
Because the sciatic nerve travels from the lumbar spine all the way into the leg, identifying what causes sciatica in a given patient requires evaluating the entire functional pathway of the nerve. Some of the most common causes include:
Herniated or Bulging Discs
A lumbar disc herniation can irritate or compress one of the nerve roots that eventually contributes to the sciatic nerve. For example, a disc problem at L4-L5 or L5-S1 may produce pain, numbness, tingling, or weakness extending into the leg or foot.
MRI is useful to identify these conditions. However, an abnormal MRI alone is insufficient to determine the source of a patient’s symptoms. This is because disc bulges and other degenerative changes in the spine are common, with a majority of adults over 30 showing degenerative findings on an MRI, many with no symptoms at all. What we need is positive imaging findings that match the patient’s symptoms and physical examination.
Lumbar Spinal or Foraminal Stenosis
The nerves exiting the lumbar spine travel through relatively small openings called neural foramina. Arthritis, disc degeneration, bone spurs, ligament thickening, and other structural changes can reduce this space (called neuroforaminal narrowing), compressing the nerve.
When a nerve becomes compressed, it gets irritated, resulting in symptoms that closely resemble those caused by a herniated disc, described as sciatica.
Piriformis and Deep Gluteal Syndrome
The sciatic nerve passes through the deep gluteal region, where it travels in close proximity to the piriformis muscle, tendons, and connective tissues. In some patients, the nerve can become irritated, compressed, or restricted along this route.
Similar to the degenerative spinal causes described above, this results in compression of the nerve, but the culprit is muscle fascia rather than bone or disc. Because soft tissue like muscle and tendon is harder to see under MRI imaging, providers often miss these causes of sciatica, making them woefully underdiagnosed.
These issues are often called piriformis syndrome, although the broader term deep gluteal syndrome may be more accurate to describe the different structures capable of irritating the sciatic nerve in this area.
Patients may experience deep buttock pain, pain while sitting, or symptoms radiating down the leg that closely resemble lumbar radiculopathy. Similar to disc and stenosis issues, this involves
Sacroiliac Joint Dysfunction
The sacroiliac, or SI, joint connects the pelvis to the sacrum at the base of the spine.
SI joint dysfunction can produce pain in the lower back, buttock, hip, and sometimes the leg. Although SI joint pain is not necessarily caused by direct compression of the sciatic nerve, its referral pattern can closely resemble sciatica.
This is an important distinction because treating the lumbar spine, or muscle issues along the root of the sciatic nerve, will not resolve sciatica symptoms originating from the SI joint.
Peripheral Nerve Entrapment
Sciatica symptoms may also occur farther down the nerve pathway. Peripheral nerves that branch from the sciatic nerve can become irritated or restricted by muscles, fascia, scar tissue, or other surrounding structures. In these cases, treating the lumbar spine may do very little because the actual source of irritation is somewhere else.
This is one reason a detailed understanding of peripheral nerve anatomy is critical when evaluating persistent sciatica.
Why Some Sciatica Treatments Don’t Work
Traditional treatments for sciatica often follow a predictable progression: medications, physical therapy, steroid injections, and eventually surgery for patients who do not improve.
Each of these treatments can be appropriate in the right situation. But the problem is that treatment often starts, or progresses, before the actual pain generator has been identified.
A lumbar epidural injection may provide excellent relief when inflammation surrounding a spinal nerve root is responsible for the symptoms; but it is unlikely to solve a mechanical entrapment of the sciatic nerve in the deep gluteal region, for example. Similarly, treating the piriformis is unlikely to resolve symptoms caused by significant compression of a lumbar nerve root.
This is why the diagnosis is the most important part of sciatica treatment.
The question should never be: “how do we treat sciatica?” But rather “why does this particular patient have sciatica?”
The Role of Diagnostic Ultrasound
MRI and X-ray provide important information about the spine and pelvis, but they are static images, meaning they do not show how the structures of the body look while moving in space, twisting, turning, and sitting under load, as we generally are. To visualize our actual anatomy, we turn to more sensitive tools like ultrasound.
At Compass Pain and Wellness, we also use high-resolution diagnostic musculoskeletal ultrasound to evaluate structures dynamically and, when appropriate, examine portions of peripheral nerves along their anatomical course.
Ultrasound is a difficult tool to master, but in the right hands, it allows a trained physician to evaluate nerves, muscles, tendons, ligaments, fascia, and other soft tissues in real time, as the body moves. This is especially valuable when a patient’s symptoms may originate outside of the lumbar spine.
The ultrasound skills of your physician become particularly important with treatments such as nerve hydrodissection.
Nerve Hydrodissection for Sciatica
When a peripheral nerve becomes irritated or restricted by the tissues surrounding it, ultrasound-guided nerve hydrodissection may be considered in appropriately selected patients.
Hydrodissection involves precisely placing fluid around a nerve under ultrasound guidance. The goal is to separate the nerve from surrounding fascia or other tissues that may be restricting its normal movement, freeing the entrapped nerve and alleviating your pain.
Rather than simply placing medication somewhere near the painful area, the physician visualizes the nerve and surrounding anatomy in real time. This requires considerable ultrasound skill.
Nerves can be small and may lie immediately adjacent to arteries, veins, muscles, tendons, and other important structures. Successful hydrodissection therefore depends on understanding both the three-dimensional anatomy and its appearance under ultrasound.
At Compass, ultrasound is not simply used to confirm needle placement. It can be part of the diagnostic process itself.
Can PRP and Orthobiologics Help Sciatica?
For certain patients, their pain generator may involve instability or injury involving the supporting structures of the spine, pelvis, or hip, which contribute to abnormal mechanics that cause irritation of surrounding tissues.
For these patients, platelet-rich plasma (PRP) and other orthobiologic treatments may be considered as part of a broader treatment strategy.
PRP is prepared from a patient’s own blood and contains concentrated platelets that release growth factors and signaling proteins involved in the body’s healing response. These growth factors can be used in specific ways to reduce nerve inflammation for immediate relief, and to structurally repair the body to a more stable state, for a long term solution to the underlying cause of the nerve irritation.
Depending on the diagnosis, treatment might focus on injured ligaments, tendons, joints, or other musculoskeletal structures contributing to abnormal mechanics and nerve irritation. Precision matters. The right treatment placed into the wrong structure is still the wrong treatment.
Treat the Cause, Not Just the Sciatica
Sciatica is ultimately a description of a symptom pattern rather than a diagnosis.
For some patients, the source is obvious. For others, especially those who have already tried physical therapy, medications, injections, or even surgery without lasting improvement, a more detailed evaluation is necessary.
At Compass Pain and Wellness, our approach combines advanced imaging, physical examination, diagnostic musculoskeletal ultrasound, and interventional diagnostics to identify the structures actually responsible for a patient’s symptoms.
Treatment can then be matched to the diagnosis and may include physical rehabilitation, image-guided injections, nerve hydrodissection, PRP or other orthobiologic procedures, conventional interventional pain treatments, or surgical consultation when appropriate.
Knowing where the pain travels is only the beginning. What causes sciatica in each patient is the real question, and the answer is what makes lasting relief possible.
