Sacroiliitis: Conditions That Mimic Its Symptoms and How to Diagnose

What mimics sacroiliitis?

Sacroiliitis, inflammation of one or both sacroiliac (SI) joints, presents with pain in the low back, buttocks, and sometimes down the leg, making it easily confused with a variety of other musculoskeletal, neurological, and inflammatory conditions.

Understanding Sacroiliitis

The sacroiliac joints are located where the sacrum (the triangular bone at the base of the spine) meets the iliac bones of the pelvis. These joints are crucial for transferring weight between the upper body and the legs, providing stability, and absorbing shock. While they have limited movement, dysfunction or inflammation can lead to significant pain.

Symptoms of sacroiliitis typically include:

• Pain: Often localized to the low back, buttocks, or groin, and can radiate down the back of the thigh or into the hip.
• Aggravating Factors: Pain often worsens with prolonged sitting or standing, standing on one leg, climbing stairs, running, or certain movements like turning in bed.
• Stiffness: Especially after periods of inactivity.

Causes can range from inflammatory conditions (e.g., ankylosing spondylitis, psoriatic arthritis), degenerative changes (osteoarthritis), trauma, infection, or biomechanical stress (e.g., leg length discrepancy, pregnancy).

Common Mimickers of Sacroiliitis

Due to the diffuse nature of low back and buttock pain, many conditions can mimic sacroiliitis, leading to diagnostic challenges. Accurate differentiation requires a thorough history, physical examination, and sometimes diagnostic imaging.

• Lumbar Radiculopathy (Sciatica): Pain radiating from the lower back down the leg, often due to compression or inflammation of a spinal nerve root. While SI joint pain can refer down the leg, true radiculopathy typically involves specific dermatomal patterns of numbness, tingling, or weakness.
• Lumbar Disc Herniation: A bulging or ruptured intervertebral disc in the lower spine can compress nerve roots, causing symptoms similar to sciatica, including low back, buttock, and leg pain.
• Lumbar Facet Joint Arthropathy/Syndrome: Degeneration or inflammation of the small joints connecting the vertebrae in the lumbar spine. Pain is often localized to the low back, can be unilateral, and may worsen with extension of the spine.
• Piriformis Syndrome: A condition where the piriformis muscle, located deep in the buttock, irritates or compresses the sciatic nerve. This causes deep buttock pain that can radiate down the leg, closely resembling SI joint pain or sciatica.
• Greater Trochanteric Pain Syndrome (Trochanteric Bursitis/Gluteal Tendinopathy): Pain and tenderness over the outer aspect of the hip (greater trochanter). While distinct from SI joint pain, referred pain patterns or co-existing conditions can confuse the diagnosis.
• Hip Joint Pathology (e.g., Osteoarthritis, Labral Tear, Femoroacetabular Impingement): Degenerative changes or structural damage within the hip joint can cause pain in the groin, lateral hip, or buttock. Pain is often exacerbated by hip movements, unlike SI joint pain which is more affected by weight-bearing or SI joint specific movements.
• Myofascial Pain Syndrome: Presence of trigger points in muscles of the low back, buttocks (e.g., gluteus medius/minimus, quadratus lumborum, piriformis), or hip can refer pain to areas that overlap with SI joint pain patterns.
• Sacral Stress Fracture: A rare but possible cause of localized sacral or buttock pain, particularly in athletes or individuals with osteoporosis. Pain is usually severe and localized.
• Infection (e.g., Sacroiliac Joint Infection, Spinal Epidural Abscess): Though uncommon, an infection in or around the SI joint can cause severe pain, fever, and other systemic symptoms.
• Tumors (Primary or Metastatic): Malignant growths in the sacrum, pelvis, or surrounding soft tissues can cause localized pain that may mimic musculoskeletal conditions. This is a red flag, especially with unexplained weight loss or night pain.
• Referred Pain from Visceral Organs: Conditions affecting pelvic organs (e.g., gynecological issues, prostate problems, inflammatory bowel disease) can sometimes refer pain to the low back or buttock region.

Why Misdiagnosis Occurs

The high rate of misdiagnosis or delayed diagnosis for sacroiliitis stems from several factors:

• Overlapping Pain Patterns: The anatomical proximity of the SI joint to the lumbar spine, hip, and surrounding musculature means pain from different structures can present in similar locations.
• Non-Specific Symptoms: Many symptoms of sacroiliitis (low back pain, buttock pain) are common to a wide array of conditions.
• Complexity of the Lumbopelvic-Hip Region: This area is a complex biomechanical unit, and dysfunction in one area can impact others.
• Lack of a Definitive Diagnostic Test: Unlike some conditions that can be clearly identified with a single imaging scan, SI joint dysfunction is often a diagnosis of exclusion, relying heavily on clinical findings and response to targeted interventions.

Key Differentiating Factors

A skilled healthcare professional will employ various methods to differentiate sacroiliitis from its mimickers:

• Detailed History Taking: Inquiring about the exact location, quality, and aggravating/alleviating factors of the pain; presence of neurological symptoms (numbness, tingling, weakness); bowel/bladder changes; systemic symptoms (fever, weight loss); and medical history (e.g., inflammatory conditions, trauma).
• Comprehensive Physical Examination:
  • Palpation: Tenderness directly over the SI joint vs. lumbar spine, hip, or muscle bellies.
  • Provocation Tests: Specific SI joint provocation tests (e.g., Faber test, Gaenslen's test, Thigh Thrust, Distraction, Compression) aim to reproduce SI joint pain. These are contrasted with tests for lumbar spine (e.g., Straight Leg Raise) or hip pathology (e.g., FADIR, scour test).
  • Neurological Exam: Assessing sensation, motor strength, and reflexes helps rule out nerve root compression from the lumbar spine.
  • Gait Analysis: Observing walking patterns for compensatory movements.
• Imaging Studies: While X-rays, MRI, or CT scans may not definitively diagnose SI joint dysfunction, they are crucial for ruling out other causes of pain such as fractures, tumors, severe degenerative changes in the lumbar spine or hip, or inflammatory sacroiliitis associated with spondyloarthritis.
• Diagnostic Injections: A highly precise injection of an anesthetic into the SI joint, guided by fluoroscopy or ultrasound, can be both diagnostic and therapeutic. If the pain significantly decreases after the injection, it strongly suggests the SI joint as the pain source.

When to Seek Professional Evaluation

It is crucial to seek professional medical advice if you experience:

• Persistent low back, buttock, or hip pain that lasts more than a few days or weeks.
• Pain that worsens or does not improve with rest or over-the-counter pain relief.
• Accompanying neurological symptoms such as numbness, tingling, weakness, or changes in bowel/bladder function (these are "red flag" symptoms requiring urgent evaluation).
• Systemic symptoms like unexplained fever, night sweats, or unintentional weight loss.
• A history of trauma or known inflammatory conditions.

Conclusion

The complex anatomy and overlapping pain patterns of the lumbopelvic-hip region make the diagnosis of sacroiliitis challenging. Many conditions can mimic its symptoms, necessitating a thorough and systematic approach to diagnosis. For fitness enthusiasts, personal trainers, and student kinesiologists, understanding these potential mimickers is essential for appropriate screening, referral, and ultimately, effective management of low back and buttock pain. An accurate diagnosis, often achieved through a multidisciplinary approach involving physical therapists, chiropractors, and physicians, is the cornerstone of effective treatment and improved quality of life.