A Guide to SI Joint Pain: Why It’s Underdiagnosed and How Surgical Fixation Helps

Despite advanced imaging technologies, SI joint dysfunction often hides in plain sight, evading CT and MRI scans and leaving patients without answers until a careful physical exam, detailed history, and targeted diagnostic injections finally reveal the true source of their pain.

Understanding SI Joint Pain

The sacroiliac (SI) joint, located where the sacrum meets the iliac bones of the pelvis, plays a crucial role in transferring forces between the spine and lower body. Although small, it bears immense biomechanical stress every day. When inflammation, degeneration, or instability affects this joint, the result can be chronic SI joint pain, a condition often mistaken for lumbar spine or hip pathology.

Studies suggest that SI joint dysfunction accounts for up to 25% of lower back pain cases, yet it frequently goes unrecognized. Because symptoms overlap with other musculoskeletal issues, patients often endure months or years of ineffective treatment before receiving the correct diagnosis.

Why SI Joint Dysfunction Is Underdiagnosed

The challenge in diagnosing SI joint pain lies in its nonspecific presentation. Patients typically report pain in the lower back, buttocks, or posterior thigh, regions also affected by lumbar disc herniation or hip osteoarthritis. Even imaging can be inconclusive; radiographs and MRIs may not clearly reveal inflammation or instability at the SI joint.

Overlapping Symptoms

Dull, aching pain radiating to the lower back, hip, or groin
Increased discomfort after prolonged standing, sitting, or climbing stairs
Asymmetrical pain or tenderness near the posterior superior iliac spine

Because these symptoms mimic other spinal or hip disorders, SI joint dysfunction often becomes a diagnosis of exclusion. Clinicians may focus on the lumbar spine first, delaying appropriate care.

Limitations of Imaging Alone

Standard imaging doesn’t always correlate with pain. Even advanced modalities like CT or MRI may miss subtle joint changes or early instability. Consequently, diagnostic precision depends on a combination of physical assessment, patient history, and confirmatory injections that temporarily relieve pain when the SI joint is anesthetized.

How SI Joint Pain Is Diagnosed

Accurate diagnosis typically requires a structured, multi-step approach:

Physical Examination: Provocative maneuvers, such as the FABER or Gaenslen test, help reproduce pain associated with SI joint dysfunction.
Diagnostic Injections: Fluoroscopically guided injections of local anesthetic confirm the joint as the pain generator when relief exceeds 75%.
Elimination of Other Causes: Ruling out lumbar radiculopathy, spinal stenosis, and hip pathology ensures diagnostic accuracy.

This comprehensive evaluation allows clinicians to identify true SI joint dysfunction and tailor treatment accordingly.

Conservative Treatments for SI Joint Pain

Before surgery is considered, most patients begin with non-operative therapies aimed at reducing inflammation and improving joint stability. Common options include:

Physical Therapy: Focused on core strengthening and pelvic stabilization exercises.
Medications: NSAIDs and corticosteroid injections to control inflammation and pain.
Bracing: SI belts or orthoses can temporarily reduce movement and relieve symptoms.

While conservative care helps many, some patients continue to experience debilitating pain that limits function and quality of life. For those individuals, surgical fixation or fusion may offer lasting relief.

When Surgery Becomes the Solution

Surgical treatment for SI joint dysfunction is typically reserved for patients who:

Experience persistent pain despite 6+ months of conservative management
Have confirmed SI joint pathology through diagnostic injections
Show functional limitations affecting daily activity or mobility

Advancements in SI joint fixation and fusion techniques have made surgery more predictable, less invasive, and more successful than in the past. These procedures aim to stabilize the joint, promote fusion, and eliminate the source of motion-related pain.

Learn how 3D printed pedicle screw design improves strength, osseointegration, and precision.

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What Is SI Joint Fixation?

SI joint fixation involves implanting one or more devices across the sacroiliac joint to limit abnormal motion and allow bone fusion. Using minimally invasive surgical approaches, the surgeon inserts specialized implants, typically made from titanium, through a small incision under fluoroscopic guidance.

The implants achieve stabilization through a combination of:

Mechanical fixation: Immediate joint stabilization to reduce micromotion
Biologic fusion: Encouraging bone growth across the joint for long-term stability

This approach reduces recovery time, minimizes tissue disruption, and allows many patients to resume light activity within weeks.

How SI Fusion Implants Work

SI fusion implants are designed to provide both structural integrity and biological integration. Many modern systems, including those from Eminent Spine, utilize porous titanium and 3D-printed architecture to mimic cancellous bone, encouraging rapid osseointegration.

Key design features include:

Surface Porosity: Promotes bone growth and long-term fixation
Optimized Thread Geometry: Enhances grip within dense cortical bone
Anatomical Sizing: Accommodates a range of patient anatomies and surgical techniques

Together, these characteristics lead to faster fusion, stronger stability, and more predictable outcomes, both intraoperatively and postoperatively.

Is SI Joint Pain Surgery Effective?

Clinical studies consistently show that minimally invasive SI joint fixation provides significant pain relief and functional improvement for appropriately selected patients. Reported benefits include:

Reduced pain scores by more than 50% within six months post-op
Improved walking tolerance and sitting comfort
Decreased dependence on pain medications

While individual outcomes vary, success largely depends on proper diagnosis, surgical technique, and implant design. For patients with confirmed joint dysfunction, fixation offers one of the most durable solutions available.

The Future of SI Joint Surgery

The increasing recognition of SI joint dysfunction is reshaping how spinal and orthopedic surgeons approach chronic low back pain. As awareness grows, additive manufacturing and implant innovation will continue to refine surgical options, offering even more effective solutions for long-term stabilization and pain relief.

With continued advancements in material science, imaging, and surgical navigation, SI joint fixation will likely become a standard component of comprehensive spinal care—providing patients with durable, life-changing results.

Eminent Spine’s SI Joint Solutions

At the forefront of spinal innovation, Eminent Spine has applied its expertise in titanium additive manufacturing to advance SI joint fusion technology. Our SI implant systems integrate the same engineering principles that define its industry-leading pedicle screw and interbody platforms—strength, precision, and biological compatibility.

Key Features of Eminent Spine’s SI Fusion System:

3D-Printed Titanium Design: Replicates bone structure for optimal osseointegration
Threaded Fixation Profile: Ensures immediate mechanical stability
Minimally Invasive Delivery: Reduces operative time and postoperative discomfort

By combining surgeon feedback with advanced biomaterial engineering, Eminent Spine delivers SI joint fixation systems that support superior outcomes and long-term fusion success.