Sciatica or SI Joint Dysfunction? What May Be Causing Your Buttock and Leg Pain

By Dr. Stephen Ford

Buttock and leg pain is often labeled “sciatica,” but that description does not always mean a spinal nerve root is being compressed. Radicular sciatica often involves pain traveling from the low back or buttock into the leg and may extend below the knee, sometimes with numbness, tingling, weakness, or reflex changes, while sacroiliac (SI) joint–related pain is more often centered in one buttock or the pelvic girdle and may refer into the thigh or groin. These conditions can feel similar, and a careful examination is usually more useful than symptoms or imaging alone.

What is the difference between sciatica and SI joint–related pain?

“Sciatica” is commonly used to describe pain that travels from the low back or buttock into the leg. Clinically, radicular sciatica refers to irritation or compression of a lumbar nerve root, often involving a disc herniation or another source of narrowing around the nerve.

The SI joints connect the base of the spine with the pelvis. They transfer load between the trunk and legs during walking, running, lifting, and single-leg activities. Pain from this region may be associated with the joint, surrounding ligaments, or nearby muscles and can refer into the buttock, posterior thigh, lateral hip, or groin.

The distinction is important, but it is not always clean. Disc, SI joint, facet joint, hip, and muscle-related sources may overlap or coexist. A person can also have a lumbar disc finding on imaging without that finding being the primary source of symptoms.

How the symptoms may differ

Features that may suggest radicular sciatica

Radicular symptoms often follow a recognizable nerve-root distribution rather than remaining in one small area. Common features may include:

• Sharp, burning, electric, or shooting pain
• Pain extending below the knee into the calf, ankle, or foot
• Numbness or tingling in a band-like or dermatomal pattern
• Weakness in a specific movement, such as lifting the foot or pushing off the toes
• A reduced reflex compared with the other side
• Leg pain reproduced by certain nerve-tension or spinal movements

Coughing, sneezing, straining, prolonged sitting, or bending may aggravate symptoms for some people, although these patterns are not diagnostic on their own.

Features that may suggest SI joint–related pain

SI joint–related symptoms are often more localized around one side of the low back, buttock, or pelvic girdle. They may include:

• Pain near the bony area just below and slightly inward from the back of the pelvis
• Buttock pain that is worse with standing, stairs, or single-leg loading
• Pain when rolling over in bed or shifting weight onto one leg
• Referral into the posterior thigh, lateral hip, or groin
• A history of a fall onto the buttocks or a sudden change in training load
• Little or no objective numbness, weakness, or reflex change

SI joint pain can sometimes travel below the knee and imitate sciatica. That is why pain location alone cannot establish the diagnosis.

How a clinician evaluates the difference

A useful examination begins with the history. A clinician may ask:

• Where did the symptoms begin?
• Does the pain travel below the knee?
• Is there numbness, tingling, or measurable weakness?
• What happens with sitting, standing, walking, stairs, bending, or coughing?
• Was there a fall, collision, lifting event, or recent change in training volume?
• Are symptoms improving, stable, or progressively worsening?

The physical examination then looks at several systems rather than relying on one test.

For possible radicular sciatica, the examination may include strength testing, sensation, reflexes, gait, and nerve-tension tests such as the straight-leg raise. A positive nerve-tension test is more meaningful when it reproduces the person’s familiar below-knee symptoms and matches other neurologic findings.

For possible SI joint–related pain, a clinician may assess the lumbar spine, hip, pelvic movement, gait, and a cluster of SI joint provocation tests. These may include:

• Thigh thrust
• FABER
• Pelvic compression
• Pelvic distraction
• Gaenslen’s test
• Sacral thrust

Research and clinical guidelines commonly support using a combination of provocation tests. Three or more positive tests that reproduce the patient’s familiar pain may increase confidence that the SI region is contributing to symptoms. No single test should be treated as definitive.

A clinician may also examine the hip and groin, especially when pain is provoked by hip rotation or when symptoms developed after a change in running, cutting, squatting, or field-sport activity. Our guide to common sources of groin and hip pain provides additional context for that overlap.

Why imaging may not settle the question

Imaging can be valuable, but it must be interpreted alongside the examination.

MRI may show disc bulges, degenerative changes, or narrowing around a nerve. These findings can be relevant when they match the person’s symptoms and neurologic examination. However, similar findings are also common in people who have no pain. An image should not automatically be treated as the explanation for every symptom.

For suspected mechanical SI joint pain, X-rays, CT scans, and MRI often do not confirm the pain source by themselves. Imaging may be appropriate to evaluate fracture, inflammatory disease, infection, tumor, or another condition, but it may not identify routine mechanical SI joint pain with certainty.

For many people with uncomplicated low back or leg pain, guidelines do not recommend immediate routine imaging. Further imaging may be considered when symptoms are severe or persistent, neurologic deficits are progressing, serious disease is suspected, or the result would change management.

When the clinical picture remains unclear, some specialists consider an image-guided SI joint injection with local anesthetic a reference standard for confirming whether the joint is contributing meaningfully to pain. This is not a first-line test for everyone and should be considered by an appropriate medical specialist when the result would inform further care.

When the sources overlap

The body is not required to choose only one pain source.

A disc-related problem and SI joint irritation may coexist. Facet joints in the low back can also refer pain into the buttock and upper thigh. Hip conditions, hamstring or gluteal injuries, and pelvic-floor or abdominal sources may add further complexity.

This is why a good evaluation should not focus exclusively on the label “sciatica” or “SI joint dysfunction.” The more useful questions are:

1. Is there evidence of nerve-root involvement?
2. Where is the person’s familiar pain reproduced?
3. Which movements or loads increase symptoms?
4. Are there objective neurologic changes?
5. Are multiple structures likely contributing?
6. Would imaging, referral, or diagnostic testing change the plan?

The goal is not to force symptoms into one category. The goal is to make the safest and most useful next decision.

Conservative care: rebuild capacity instead of chasing a label

When serious conditions and progressive neurologic problems have been ruled out, conservative care may be appropriate for many people. The plan should match the examination, irritability of symptoms, current fitness level, and daily demands.

Common components may include:

• Maintaining tolerable daily movement rather than prolonged bed rest
• Temporarily modifying painful lifting, running, cutting, or sitting loads
• Gradual lumbopelvic and hip strengthening
• Trunk endurance and single-leg control
• Hip mobility when a restriction is relevant to the movement problem
• Movement retraining for bending, lifting, stairs, and sport-specific tasks
• A staged return to running, training, or competition

The exercise selection should be individualized. A bridge, side plank, split squat, hip hinge, or walking progression may be useful for one person and too demanding for another. Symptoms during exercise should be monitored over the following 24 hours, with the workload adjusted when the response is consistently worse.

Chiropractic care, soft-tissue treatment, and therapeutic exercise may be included as part of a broader plan when appropriate. These approaches may help improve movement tolerance and support a return to activity, but they should not replace evaluation for neurologic deficits or serious disease.

Our article on joint instability, strength training, and proprioception explains why strength and movement control can matter when symptoms are affected by loading and position. You can also explore the Dynamic Spine & Performance Center blog for additional recovery and mobility education.

Red flags: when to seek urgent medical care

Seek urgent medical attention for symptoms that may indicate cauda equina syndrome, infection, fracture, cancer, or another serious condition. Warning signs include:

• Numbness in the saddle area around the inner thighs, groin, or buttocks
• New loss of bladder or bowel control
• Difficulty starting urination or inability to empty the bladder
• Progressive weakness in both legs
• Rapidly worsening neurologic symptoms
• Fever or feeling acutely unwell with back pain
• Unexplained weight loss
• A history of cancer with new or unexplained back pain
• Significant trauma, especially with increased fracture risk
• Severe or persistent night pain that is not affected by position
• Progressive weakness, numbness, or loss of coordination

These symptoms require medical evaluation rather than a routine exercise progression or manual therapy visit.

Key takeaways

• Buttock and leg pain is not automatically radicular sciatica.
• Radicular sciatica is more likely when pain follows a nerve-root pattern and is accompanied by numbness, weakness, or reflex changes.
• SI joint–related pain is often one-sided and centered in the buttock or pelvic girdle, but it can produce sciatica-like symptoms.
• Three or more positive SI joint provocation tests may improve diagnostic confidence.
• Imaging findings are common and should be matched to the examination; imaging alone often does not settle the diagnosis.
• Disc, SI joint, facet, hip, and muscle-related sources can overlap.
• Graded activity, load modification, hip and trunk strengthening, and movement retraining may support recovery when conservative care is appropriate.
• Saddle numbness, bladder or bowel changes, progressive weakness, fever, significant trauma, or other red flags require urgent medical care.

Buttock or Leg Pain That Isn’t Improving?

If buttock, hip, low-back, or leg pain is interfering with walking, exercise, work, or daily activities, identifying the likely source of the symptoms is an important first step.

Dr. Stephen Ford at Dynamic Spine and Performance Center in Katy, Texas evaluates and treats musculoskeletal conditions involving the low back, pelvis, hips, and lower extremities.

Contact DSPC to schedule an evaluation.

Clinical disclaimer

This article is for general educational purposes and is not a diagnosis or individualized treatment plan. Buttock or leg pain can have several causes. A qualified healthcare professional should evaluate persistent, severe, worsening, or neurologic symptoms. Seek urgent care for the red flags described above.

If buttock or leg pain is limiting your training, work, sleep, or daily movement, schedule an evaluation with Dynamic Spine & Performance Center. Our team can assess your movement and neurologic status, discuss whether conservative care is appropriate, and help build a progressive plan around your goals.

Sources

• Sciatica-like symptoms and the sacroiliac joint: clinical features and differential diagnosis, European Spine Journal, 2013. Reviews how SI joint pain may mimic radicular symptoms and discusses clinical differentiation.
• Low back pain of disc, sacroiliac joint, or facet joint origin: a diagnostic accuracy systematic review, eClinicalMedicine, 2023. Examines the limits of clinical tests and diagnostic accuracy across common low back pain sources.
• Successful Diagnosis of Sacroiliac Joint Dysfunction: Journal of Pain Research, 2021. Reviews diagnostic approaches, including provocation test clusters and diagnostic injections.
• ASPN best practice guideline for the treatment of sacroiliac disorders: Journal of Pain Research, 2024. Provides best-practice recommendations for assessment and management of SI disorders.
• Evidence-Based Diagnosis and Treatment of the Painful Sacroiliac Joint: Laslett, Journal of Manual & Manipulative Therapy, 2008. Discusses provocation testing and conservative management.
• Recommendations for Diagnosis and Treatment of Lumbosacral Radicular Pain: A Systematic Review of Clinical Practice Guidelines, Journal of Clinical Medicine, 2021. Summarizes guideline recommendations for evaluating and managing radicular pain.
• NICE guideline: Low back pain and sciatica in over 16s, Evidence-based guidance on assessment, imaging, self-management, exercise, and referral considerations.