Sacroiliitis: Causes, Diagnosis and Treatment Options

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The sacroiliac joint, often underestimated, plays a crucial role in the biomechanics of the pelvis and spine. When this joint becomes inflamed, it is called sacroiliitis, a condition that can generate significant pain and limit quality of life. Understanding sacroiliitis, its causes, symptoms, and treatment options is fundamental for effective management. This article aims to deeply explore sacroiliitis causes and treatment, offering a comprehensive overview based on decades of clinical experience and the latest scientific evidence.

Anatomy and Function of the Sacroiliac Joint

The sacroiliac joint is where the sacrum connects to the pelvis, transmitting forces between the spine and legs while allowing minimal movement for stability and shock absorption. The sacroiliac joints (SIJs) are a pair of joints located on either side of the spine, where the sacrum (the triangular base of the spine) meets the ilium (the upper and wider part of the pelvic bone). Although they are considered diarthrodial (synovial) joints, their mobility is extremely limited, typically by a few degrees. This limited mobility is essential for their primary function: load transmission.

For a complete overview, see the comprehensive guide to back pain and spine.

The SIJs act as shock absorbers, distributing the forces generated during walking, running, and other activities involving the trunk and lower limbs. They transfer weight from the spine to the pelvis and lower limbs, and vice versa. The stability of these joints is ensured by a robust network of intrinsic and extrinsic ligaments, which envelop and reinforce them. Among these, the anterior, posterior, and interosseous sacroiliac ligaments are the most important.

The articular surface is irregular and features hyaline cartilage on the sacral side and fibrocartilage on the iliac side. This conformation, along with the joint capsule and ligaments, contributes to creating a “form closure” and “force closure” mechanism, which stabilizes the joint under load. Dysfunction or inflammation of these structures can severely compromise their ability to bear weight and absorb impacts, leading to pain and disability.

Sacroiliitis: Definition and Types

Sacroiliitis is the inflammation of one or both sacroiliac joints. This condition can manifest in an acute form, with a sudden onset and intense symptoms, or in a chronic form, with persistent and fluctuating pain over time. The inflammation can affect the joint capsule, cartilage, surrounding ligaments, or subchondral bone.

There are different types of sacroiliitis, classified according to the underlying cause:

• Mechanical or Dysfunctional Sacroiliitis: This is the most common form and is not associated with a systemic disease. It occurs due to excessive or repetitive mechanical stress on the joint, postural misalignments, muscular imbalances, or trauma. There is no systemic inflammation, but rather a local inflammatory reaction due to overload or altered biomechanics.
• Rheumatic Sacroiliitis or Spondyloarthropathy: This form is associated with systemic inflammatory diseases, particularly seronegative spondyloarthropathies. The most common include ankylosing spondylitis, psoriatic arthritis, reactive arthritis, and arthritis associated with inflammatory bowel diseases (such as Crohn’s disease or ulcerative colitis). In these cases, sacroiliitis is often bilateral and symmetrical, and can lead to progressive structural changes in the joint, up to fusion (ankylosis).
• Infectious Sacroiliitis: Less common, it is caused by a bacterial infection (e.g., staphylococcus, tuberculosis) that reaches the sacroiliac joint, often hematogenously or by contiguity from a nearby infection.
• Post-Traumatic Sacroiliitis: A direct consequence of significant trauma to the pelvis or lumbosacral spine, such as a fall, a car accident, or a fracture.
• Pregnancy-Related Sacroiliitis: During pregnancy, hormonal changes (particularly the increase in relaxin) lead to a loosening of the pelvic ligaments, including the sacroiliac ones. This, combined with weight gain and postural changes, can cause instability and inflammation of the joint.

The distinction between these types is crucial for setting the most appropriate treatment, as therapeutic strategies vary significantly depending on the cause.

Sacroiliitis Causes: Triggering and Risk Factors

The causes of sacroiliitis are multiple and can be grouped into different categories. Understanding the triggering and risk factors is essential for prevention and management.

Mechanical/Biomechanical Causes

These are the most frequent causes of non-inflammatory or dysfunctional sacroiliitis:

• Biomechanical Dysfunction: Alterations in the mobility of the sacroiliac joint, either in excess (hypermobility) or in deficiency (hypomobility). Hypermobility can result from ligamentous laxity (e.g., post-pregnancy, trauma) or muscular imbalances that fail to stabilize the joint. Hypomobility can be caused by muscular stiffness, adhesions, or cartilage alterations.
• Muscular Imbalances: Weakness of core stabilizing muscles (deep abdominals, multifidus, pelvic floor) or glutes, and/or excessive tension in muscles such as the iliopsoas, piriformis, or hamstrings, can alter SIJ mechanics.
• Leg Length Discrepancy: A significant difference in leg length can alter pelvic alignment and increase stress on one of the sacroiliac joints.
• Postural and Gait Alterations: Incorrect postures maintained for a long time, such as sitting asymmetrically or an altered gait (e.g., limping), can overload the joint.
• Direct Trauma: Falls on the coccyx or gluteus, car accidents, or sports injuries can cause damage to the ligaments or capsule of the SIJ, triggering an inflammatory process.
• Previous Surgical Interventions: Spinal surgery (e.g., lumbar fusion) can alter pelvic biomechanics and increase stress on adjacent SIJs.
• Pregnancy and Childbirth: As mentioned, hormonal and mechanical changes during pregnancy and childbirth can lead to instability and inflammation.

Inflammatory/Rheumatic Causes

These causes are systemic and require a specific medical approach:

• Ankylosing Spondylitis: The most common cause of inflammatory sacroiliitis, often bilateral and symmetrical, which can lead to joint fusion.
• Psoriatic Arthritis: Associated with cutaneous psoriasis, it can affect the SIJs.
• Reactive Arthritis (Reiter’s Syndrome): Develops in response to an infection in another part of the body (e.g., gastrointestinal or genitourinary).
• Enteropathic Arthritis: Associated with inflammatory bowel diseases such as Crohn’s disease and ulcerative colitis.
• Juvenile Idiopathic Arthritis: Can affect the SIJs in children and adolescents.

Other Causes

• Infections: Bacteria (e.g., Staphylococcus aureus, Mycobacterium tuberculosis) can infect the joint.
• Tumors: Rarely, primary or metastatic tumors can affect the sacrum or sacroiliac joint.
• Metabolic Diseases: Gout or pseudogout, although rare, can affect the SIJ.

Sacroiliitis Symptoms: How it Manifests

The cardinal symptom of sacroiliitis is pain, but its characteristics can vary widely depending on the cause and severity of the inflammation.

Pain

• Location: Pain is typically felt in the lower back, on one or both sides of the sacrum, often radiating to the buttock, groin, back of the thigh (rarely beyond the knee), and sometimes to the lower abdomen. Precise localization can help distinguish sacroiliitis from other causes of low back pain.
• Nature of Pain: It can be dull and constant, or sharp and stabbing.
• Aggravating Factors:

• Prolonged sitting: Especially on hard surfaces or in asymmetrical positions.

• Prolonged standing: Axial load can exacerbate the pain.

• Transitioning from sitting to standing: Movement that requires active stabilization of the joint.

• Climbing stairs or running: Activities that increase stress on the joint.

• Sleeping on the affected side: Compression can increase pain.

• Specific movements: Bending forward, rotating the trunk, lifting weights, or even coughing/sneezing.

• Inflammatory sacroiliitis: Pain tends to be worse in the morning and improves with movement during the day. It can wake the patient at night.

• Mechanical sacroiliitis: Pain worsens with activity and improves with rest.

Associated Symptoms

In addition to pain, sacroiliitis can present other symptoms:

• Stiffness: Feeling of stiffness in the lower back and pelvis, especially in the morning or after periods of inactivity.
• Limited Movement: Difficulty performing movements involving the pelvis and lumbar spine, such as bending or rotating.
• Weakness or Numbness: Rarely, if inflammation is severe and compresses nearby nerve structures, neurological symptoms may occur, but it is more common in cases of lumbar radiculopathy.
• Fever, General Malaise, Weight Loss: These symptoms are more common in infectious sacroiliitis or in some forms of rheumatic sacroiliitis (e.g., active ankylosing spondylitis).
• Extra-articular Symptoms: In spondyloarthropathies, symptoms such as ocular inflammation (uveitis), skin lesions (psoriasis), oral ulcers, or gastrointestinal symptoms may be present.

The variability of symptoms makes the diagnosis of sacroiliitis a challenge, often requiring careful differential evaluation to exclude other conditions with similar symptoms, such as lumbar disc herniation, spinal stenosis, piriformis syndrome, or other causes of pelvic pain.

Diagnosis of Sacroiliitis: A Complex Path

The diagnosis of sacroiliitis can be complex due to its multifactorial nature and the overlap of symptoms with other conditions of the lumbar spine and pelvis. It is a process that requires an integrated approach, combining anamnesis, physical examination, provocative tests, and, if necessary, instrumental investigations.

Anamnesis and Physical Examination

The first step is a detailed collection of the anamnesis, investigating the nature of the pain (onset, location, radiation, aggravating and alleviating factors, circadian rhythm), any previous traumas, history of rheumatic or inflammatory diseases, surgical interventions, pregnancy, and lifestyle.

The physical examination includes:

• Postural Assessment: Observation of asymmetries, misalignments of the pelvis or spine.
• Palpation: Assessment of tenderness on direct palpation of the sacroiliac joint and surrounding structures (ligaments, muscles).
• Mobility Assessment: Examination of the mobility of the lumbar spine and hips, to identify any restrictions or compensatory hypermobility.
• Neurological Assessment: Exclusion of lumbar radiculopathies through tests of sensation, strength, and reflexes.

Provocative Tests for the Sacroiliac Joint

These clinical tests aim to reproduce the typical pain of sacroiliitis by applying mechanical stress to the joint. No single test is 100% diagnostic, but a battery of positive tests increases the probability of sacroiliitis. The most common include:

• Distraction Test (Gänsle’s Test): The patient is supine, the examiner applies downward pressure on the anterior superior iliac spines.
• Compression Test (Sacroiliac Compression Test): The patient is on their side, the examiner applies downward pressure on the superior ilium.
• Thigh Thrust Test (P4 Test): The patient is supine, the hip is flexed to 90 degrees and adducted, the examiner applies an axial force through the femur towards the sacroiliac joint.
• Faber Test (Flexion, Abduction, External Rotation): The patient is supine, the affected leg is positioned with the hip flexed, abducted, and externally rotated (ankle on the opposite knee), the examiner applies pressure on the knee and the opposite iliac spine.
• Gaenslen’s Test: The patient is supine, one leg is hyperflexed to the chest, the other is extended beyond the edge of the examination table.

If at least 3-4 of these tests provoke the patient’s familiar pain, the probability of sacroiliitis is significantly higher.

Diagnostic Imaging

Imaging techniques are used to confirm inflammation, exclude other pathologies, and identify signs of rheumatic sacroiliitis.

• Standard Pelvic X-ray: Can show advanced structural changes such as erosions, sclerosis, joint space narrowing, or ankylosis, typical of chronic spondyloarthropathies. In early stages, it may be normal.
• Magnetic Resonance Imaging (MRI) of the Pelvis: It is the most sensitive examination for detecting active inflammation (bone edema, synovitis, capsulitis) in the early stages of sacroiliitis, especially rheumatic. It can also identify chronic structural changes.
• Computed Tomography (CT): Offers a detailed view of bone structures and can be useful for evaluating chronic bone changes or excluding fractures.
• Bone Scintigraphy: Can indicate areas of increased bone metabolic activity, suggesting inflammation, but is less specific than MRI.

Diagnostic Injections

The injection of a local anesthetic directly into the sacroiliac joint, guided by fluoroscopy or ultrasound, is considered the “gold standard” diagnostic. If the patient’s pain is significantly reduced (at least 50-75%) after the injection, this confirms that the sacroiliac joint is the source of the pain.

Differential diagnosis is crucial and must consider conditions such as lumbar disc herniation, spinal stenosis, piriformis syndrome, hip osteoarthritis, stress fractures of the sacrum or pelvis, and other causes of pelvic pain.

Sacroiliitis Treatment: A Multimodal Approach

The treatment of sacroiliitis is personalized and depends on the underlying cause, the severity of symptoms, and the patient’s response to therapies. The main goal is to reduce pain and inflammation, restore joint function, and prevent recurrences. A multimodal approach combining conservative, pharmacological, and, in rare cases, interventional therapies, is often the most effective.

Acute Phase: Pain and Inflammation Management

In the acute phase, the primary goal is to relieve pain and reduce inflammation.

• Relative Rest: Avoid activities that aggravate the pain. Absolute rest is generally not recommended, as it can lead to stiffness.
• Application of Ice or Heat: Ice can help reduce inflammation in the acute phase, while heat can relax tense muscles and improve circulation in the subacute/chronic phase.
• Non-Steroidal Anti-Inflammatory Drugs (NSAIDs): Can be prescribed by a doctor to reduce pain and inflammation.
• Muscle Relaxants: In case of significant muscle spasm.

Physiotherapy Treatment for Sacroiliitis

Physiotherapy is a fundamental component in the treatment of sacroiliitis, both mechanical and inflammatory (once systemic inflammation is controlled). The goal is to restore correct biomechanics, strengthen stabilizing muscles, and improve mobility.

Manual Therapy

The physical therapist can use various manual therapy techniques:

• Joint Mobilizations: Gentle techniques to restore normal mobility of the sacroiliac joint, both in cases of hypomobility and to improve stability in cases of hypermobility.
• Spinal Manipulations: In some selected cases, low-velocity, high-amplitude manipulations can be used to restore alignment and mobility.
• Muscle Energy Techniques (MET): Utilize the patient’s muscle contraction against resistance to improve mobility and reduce muscle tension.
• Myofascial Release and Therapeutic Massage: To reduce tension and spasms in surrounding muscles (e.g., piriformis, glutes, lumbar muscles).

Therapeutic Exercises

A personalized exercise program is crucial for long-term recovery.

• Mobility Exercises: Gentle movements to maintain or restore mobility of the sacroiliac joint and lumbar spine, without aggravating pain.
• Core Stabilization Exercises: Strengthening of the deep abdominal muscles, pelvic floor, and multifidi to improve trunk and pelvic stability.
• Gluteal Strengthening Exercises: The gluteal muscles (particularly the gluteus medius) are fundamental for pelvic stability.
• Stretching: Stretching of tense muscles such as the piriformis, hip flexors, hamstrings, and lumbar muscles.
• Postural Re-education: Learning correct postures for sitting, standing, and sleeping, to reduce stress on the joint.

Instrumental Physical Therapies

Can be used as an adjunct to reduce pain and inflammation:

• Tecar Therapy: Promotes tissue repair and reduces pain.
• Laser Therapy: Has anti-inflammatory and analgesic effects.
• Therapeutic Ultrasounds: Can help reduce inflammation and improve soft tissue healing.
• Electrotherapy (TENS): For pain control.

Postural Education and Ergonomics

The physical therapist will provide advice on how to modify daily activities, improve posture at work and at home, and use supports (e.g., specific cushions) to reduce stress on the sacroiliac joint.

Pharmacological Treatment

In addition to NSAIDs and muscle relaxants, the doctor may consider:

• Oral Corticosteroids: For short periods in cases of severe acute inflammation.
• Disease-Modifying Anti-Rheumatic Drugs (DMARDs): In sacroiliitis associated with spondyloarthropathies, to control the progression of systemic disease.
• Biologic Drugs: For more severe forms of spondyloarthropathies that do not respond to traditional DMARDs.

Therapeutic Injections

• Corticosteroid Injections: The injection of a corticosteroid and a local anesthetic directly into the sacroiliac joint (under ultrasound or fluoroscopic guidance) can provide significant pain and inflammation relief for a variable period. These can be repeated, but with caution due to the potential side effects of corticosteroids.
• Platelet-Rich Plasma (PRP) Injections: Some studies suggest the effectiveness of PRP for its regenerative and anti-inflammatory action, but further research is needed.

Minimally Invasive and Surgical Treatments

These options are considered only when conservative therapies fail and pain is severe and debilitating.

• Radiofrequency Ablation: Uses heat generated by radio waves to deactivate the nerves that transmit pain from the sacroiliac joint.
• Cryoablation Denervation: Similar to radiofrequency, but uses cold to block nerve transmission.
• Sacroiliac Joint Fusion: A surgical procedure that aims to stabilize the joint by fusing the sacrum and ilium. It can be performed with open or minimally invasive techniques. It is reserved for selected cases of severe chronic pain and instability that do not respond to other therapies.

The choice of treatment should always be discussed with your doctor or physical therapist, who will evaluate the specific case and propose the most appropriate therapeutic path.

Exercises for Sacroiliitis: Recovery and Prevention

Exercises are a crucial component for both recovery from sacroiliitis and prevention of recurrences. They must be performed with caution, without causing pain, and preferably under the guidance of a physical therapist.

Gentle Mobility Exercises

These exercises aim to improve flexibility and reduce stiffness without overloading the joint.

• Pelvic Tilts: Lie on your back with knees bent and feet flat on the floor. Flatten your lower back against the floor, contracting your abdominals and glutes (pelvic posterior tilt), then slightly arch your back (anterior tilt). Perform slowly for 10-15 repetitions.
• Knee-to-Chest Stretch: Lie on your back. Bring one knee to your chest, holding it with your hands, and hold the position for 20-30 seconds. Repeat with the other leg. For a deeper stretch, bring both knees to your chest.
• Trunk Rotations: Lie on your back with knees bent and feet flat on the floor. Keeping your knees together, slowly let them fall to one side, keeping your shoulders on the ground. Hold for a few seconds and return to the center. Repeat on the other side.

Core and Pelvic Stabilization Exercises

These exercises strengthen the muscles that support the sacroiliac joint.

• Bridge: Lie on your back with knees bent and feet flat on the floor, arms by your sides. Slowly lift your pelvis off the ground, contracting your glutes and abdominals, until your body forms a straight line from your shoulders to your knees. Hold for 5-10 seconds and slowly lower. Repeat 10-15 times.
• Bird-Dog: Start on all fours, with hands under shoulders and knees under hips. Keeping your core stable and back straight, simultaneously extend one arm forward and the opposite leg backward, keeping your pelvis stable. Hold for 5 seconds and slowly return. Repeat 8-10 times per side.
• Clamshells: Lie on your side with knees bent and feet together. Keeping your feet together, lift your top knee upwards, opening your legs like a clamshell. Control the downward movement. Repeat 10-15 times per side. This exercise strengthens the gluteus medius.

Stretching

Stretching tight muscles can relieve pressure on the joint.

• Piriformis Stretch: Lie on your back with knees bent and feet flat on the floor. Place the ankle of one leg on the opposite knee. Grasp the thigh of the leg on the ground and gently pull it towards your chest until you feel a stretch in your glute. Hold for 20-30 seconds per side.
• Hip Flexor Stretch: In a lunge position, with one knee on the ground and the other foot forward. Gently push your pelvis forward to feel a stretch in the front of the hip of the leg on the ground. Hold for 20-30 seconds per side.

It is essential that exercises are performed correctly and do not cause an increase in pain. If in doubt, it is always advisable to consult your doctor or physical therapist for a personalized and supervised exercise program.

Sacroiliitis Prevention

The prevention of sacroiliitis, particularly that of mechanical origin, is based on an approach aimed at maintaining correct biomechanics and stability of the pelvis and spine.

• Maintain Correct Posture: Both standing and sitting, it is essential to maintain the spine in a neutral position. Avoid sitting for long periods in asymmetrical positions (e.g., with a wallet in the back pocket).
• Regular Physical Exercise: An exercise program that includes core and gluteal strengthening and stretching can improve pelvic and spinal stability and flexibility. Activities such as Pilates, yoga, or swimming are often beneficial.
• Avoid Overload: Do not lift excessive weights and use correct lifting techniques, bending your knees and keeping your back straight.
• Weight Management: Overweight and obesity increase the load on weight-bearing joints, including the SIJ.
• Adequate Footwear: Wear comfortable and supportive shoes, especially if standing for long periods. In case of leg length discrepancy, consider using orthotics or lifts prescribed by a specialist.
• Avoid Repetitive Trauma: In sports or work activities, pay attention to repetitive or high-impact movements that may stress the joint.
• Hydration and Balanced Diet: Contribute to overall tissue health and can help reduce systemic inflammation.
• Management of Underlying Diseases: For rheumatic forms, strictly follow the rheumatologist’s therapeutic plan to control systemic inflammation and prevent joint damage.

Adopting these preventive measures can significantly reduce the risk of developing sacroiliitis or experiencing recurrences, contributing to maintaining good pelvic and spinal health.

Frequently Asked Questions (FAQ)

Conclusion

Sacroiliitis is a painful and often debilitating condition that can significantly impact quality of life. Understanding its causes, recognizing symptoms, and undertaking a targeted diagnostic and therapeutic path are fundamental steps for effective management. From manual therapy and specific exercises, to pharmacological treatments and, in selected cases, interventional procedures, a multimodal and personalized approach is key to recovery. It is essential to consult your doctor or physical therapist for an accurate diagnosis and a tailored treatment plan, in order to alleviate pain, restore function, and prevent recurrences.

Frequently Asked Questions

What is sacroiliitis?

Sacroiliitis is characterized by inflammation of the sacroiliac joint, which is located where the spine connects to the pelvis. This condition can lead to significant pain and impact an individual’s quality of life.

What is the primary function of the sacroiliac joints?

The sacroiliac joints serve as crucial shock absorbers, facilitating the transmission of weight between the spine and the lower limbs. Their limited mobility is essential for maintaining stability and distributing forces during movement.

What are the common causes of mechanical sacroiliitis?

Mechanical sacroiliitis frequently arises from factors such as excessive stress on the joint, poor posture, or muscle imbalances. Trauma to the sacroiliac joint can also be a significant contributing cause.

Why is understanding the causes of sacroiliitis important for its management?

A comprehensive understanding of sacroiliitis causes is fundamental for developing effective management strategies. Identifying the underlying factors allows for targeted interventions to alleviate pain and improve an individual’s overall quality of life.

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