Continuing Education Activity

Sacroiliitis is an inflammatory condition affecting the sacroiliac joint, a major articulation connecting the ilium and sacrum that frequently contributes to gluteal and lower back pain. The disorder may occur secondary to osteoarthritis, pregnancy, trauma, or inflammatory conditions such as spondyloarthropathies, making an accurate diagnosis essential because symptoms often overlap with other causes of lumbopelvic pain. This course reviews the anatomy and function of the sacroiliac joint; the pathophysiology and causes of sacroiliitis; clinical presentation; diagnostic evaluation; and evidence-based management strategies. Participants learn to recognize characteristic symptoms and physical examination findings, interpret relevant imaging and diagnostic studies, and apply appropriate pharmacologic, rehabilitative, and interventional treatment approaches. Emphasis is placed on identifying underlying etiologies and tailoring management to individual patient needs. Collaboration among clinicians, rheumatologists, physiatrists, orthopedic specialists, radiologists, physical therapists, nurses, and other healthcare professionals enhances diagnostic accuracy, coordinates treatment, and improves patient outcomes through comprehensive interprofessional care.

Objectives:

• Apply evidence-based principles to evaluate, diagnose, and manage sacroiliitis to reduce pain, improve function, and optimize patient outcomes.
• Differentiate sacroiliitis from other musculoskeletal, neurologic, and rheumatologic conditions that present with lower back, pelvic, or gluteal pain.
• Implement evidence-based pharmacologic, rehabilitative, and interventional management strategies for patients with sacroiliitis.
• Develop interprofessional communication and collaborative care strategies among clinicians, rheumatologists, physiatrists, orthopedic specialists, radiologists, physical therapists, nurses, and other healthcare professionals to enhance diagnostic accuracy, treatment coordination, and patient outcomes.

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Introduction

Sacroiliitis is inflammation of the sacroiliac (SI) joint, typically causing pain. Often, it is a diagnosis of exclusion. The sacroiliac (SI) joint is one of the largest joints in the body and a common source of buttock and lower back pain. It connects the bones of the ilium to the sacrum. Sacroiliitis can be particularly difficult to diagnose because its symptoms are similar to those of many other common sources of back pain. It is often overlooked as a source of back or buttock pain. Pain from this condition is often due to chronic degenerative causes, yet relatively uncommon. Sacroiliitis can be secondary to rheumatic, infectious, drug-related, or oncologic sources. Some specific examples of non-degenerative conditions that can lead to sacroiliitis are ankylosing spondylitis, psoriatic arthropathy, Bechet disease, hyperparathyroidism, and various pyogenic sources.[1][2][3]

Etiology

Various conditions can cause inflammation of the SI joint, leading to significant pain. Osteoarthritis can cause degeneration of the joint, resulting in pathologic articulation and motion leading to this condition. Spondyloarthropathies themselves can cause significant joint inflammation. Pregnancy is another cause of inflammation due to the hormone relaxin, which leads to relaxation, stretching, and possible widening of the SI joint(s). The increased weight of pregnancy also causes extra mechanical stress on the joint, leading to further wear and tear. Trauma can cause direct or indirect stress and damage to the SI joint. Pyogenic sacroiliitis is the most frequently reported cause of acute sacroiliitis. Pain can originate from the synovial joint but can also originate from the posterior sacral ligaments.[4][5]

Epidemiology

Reports on the prevalence of sacroiliac pain vary widely. Some studies report a prevalence of 10% to 25% among those with lower back pain. In those with a confirmed diagnosis, the presentation of pain was ipsilateral buttock (94% cases) and midline lower lumbar area (74%). As mentioned previously, the presentation can vary. Up to 50% of cases have radiation to the lower extremity: 6% to the upper lumbar area, 4% percent to the groin, and 2% percent to the lower abdomen.[6][7]

Pathophysiology

The sacrum articulates with the ilium, which helps to distribute body weight to the pelvis. The SI joint capsule is relatively thin and often develops defects that allow fluid, such as joint effusion or pus, to leak onto surrounding structures. As surrounding muscles and structures are affected, pain can present differently because different nerve roots innervate these structures. Common pain distributions are L4 to L5 dermatomes, but pain can certainly present in dermatomes as high as L2 and as low as S3. Asymmetric pelvic motion can cause mechanical dysfunction, leading to degeneration and significant pain. Differential diagnosis includes leg-length discrepancies, a unilateral weaker limb or gluteal muscles, tight or strained surrounding muscle structures, or hip osteoarthritis.[8]

Histopathology

Common degenerative findings include destruction and fibrosis of the cartilage, and disruption, erosion, and ossification of the subchondral bone. Synovitis is also commonly found, revealing hyperplasia of the lining cells with infiltration by inflammatory cells. Degenerative enthesitis similarly reveals inflammatory cells. Infectious etiologies of sacroiliitis reveal lymphocytes, plasma cells, and fibrosis. Notably, some patients will show no histopathologic changes.

History and Physical

Sacroiliitis commonly presents as lower back pain. The pain presentation varies greatly, and patients could describe pain in one or both buttocks, hip pain, thigh pain, or even pain more distal. Patients may report that their pain is worse after sitting for prolonged periods or with rotational movements. Characterization of pain also varies widely and is commonly described as sharp and stabbing, but can also be described as dull and achy. It is very important to ascertain more than just the timing and descriptions of the pain. Ask about a history of inflammatory disorders as discussed previously. Also, obtain a thorough review of systems to evaluate for systemic symptoms, including fever, chills, night sweats, and weight loss. These symptoms are indicative of a more serious process, indicating a likely systemic illness.

Although not always obvious, inspection can reveal pelvic asymmetry. Measurement of the limbs can rule out a leg-length discrepancy. Inspect the spine for any abnormal curvatures or rotational abnormalities. Typically, the range-of-motion, neurologic, and strength testing are unremarkable, although the patient may experience pain during some of these tests.

Special provocative tests can be very helpful in reproducing the patient’s pain:

• “Fortin finger sign”: Reproduction of pain after applying a deep palpation with the 4-hand fingers posteriorly at the patient's SI joint(s).
• FABER test: Reproduction of pain after flexing the hip while also abducting and externally rotating the hip.
• Sacral distraction test: Reproduction of pain after applying pressure to the anterior superior iliac spine.
• Iliac compression test: Reproduction of pain after applying pressure downward on the superior aspect of the iliac crest.
• Gaenslen test: Reproduction of pain after having the patient flex the hip on the unaffected side and then dangle the affected leg off the examining table. Pressure is then directed downward on the leg to extend further the hip, which causes stress on the SI joint.
• Thigh thrust test: Reproduction of pain after flexing the hip and applying a posterior shearing force to the SI joint.
• Sacral thrust test: Reproduction of pain with the patient prone and then applying an anterior pressure through the sacrum.

The likelihood of SI joint-mediated pain increases as the number of positive-provocative tests increases.

Evaluation

As discussed previously, various inflammatory conditions may cause or contribute to SI joint pain. If an inflammatory condition is suspected, consider ordering a complete blood cell count, erythrocyte sedimentation rate, C-reactive protein, antinuclear antibody, human leukocyte antigen (HLA-B27), and rheumatoid factor. Although cancer is a far less common cause of sacroiliitis, if a cancerous process is suspected, consider ordering labs to assess for malignancy.[9][10]

In most clinical evaluations, common laboratory findings in the aseptic setting include:

• WBC count: Usually normal (elevated in infection/septic presentation)
• ESR: Elevated
• CRP: Elevated
• HLA-B27: About 50% to 92%% of patients with ankylosing spondylitis will be HLA-B27 positive
• Rheumatoid factor: Negative in the setting of true ankylosing spondylitis

If trauma or inflammatory causes are not suspected, radiographs are typically unnecessary, as there is usually no correlation between pain and radiographic findings. If radiographs are performed, an anteroposterior view of the pelvis/lumbar spine should be ordered. These images can show sclerosis or other degenerative changes of the SI joint. Specific sacroiliac views can also be obtained at a 25- to 30-degree angle to help delineate widening or sclerotic changes at joint margins. A CT scan can also show sclerotic changes and reveal reactive spurring or subluxation. The previously noted imaging findings are usually later changes. MRI may show subchondral edema, which is the earliest sign of sacroiliitis. PET scans can be ordered to evaluate for bony metastatic disease.

The most informative test for the diagnosis of sacroiliitis is the SI joint injection with local anesthetics and steroids. If this procedure relieves the pain, it is likely that the inflammation at this site was the cause. Potentially, a single injection or a series of injections can completely treat the pain. If the injection provided a very significant amount of pain relief, even if only for a short period, the chronic pain is likely attributable to the SI joint. In such cases, surgical intervention should be considered, as the injections localized the pain to the SI joint(s). No more than three injections should occur over a year.

Treatment / Management

Physical therapy can be very helpful if the pain is due to hypermobility. Therapy can help to stabilize and strengthen the lumbopelvic musculature. If the pain is due to immobility, physical therapy can help increase SI joint mobility. NSAIDs and muscle relaxants can be prescribed during the acute phase of presentations. These are less effective as cases become more chronic. Real-time image-guided intra-articular anesthetic/steroid injections can be performed for diagnostic and therapeutic effects. If the previous treatments do not provide adequate relief, then some providers will consider radiofrequency ablation. Usually, surgery is reserved as a last resort for patients with chronic pain. In such cases, one can consider SI joint fusion with SI screws.[11][12][13]

Differential Diagnosis

The differential diagnosis includes the following:

• Ankylosing spondylitis
• Hip tendonitis/fracture
• Piriformis syndrome
• Sacroiliac joint infection
• Trochanteric bursitis

Complications

Complications can include the following:

• Chronic back and hip pain
• Muscle wasting

Pearls and Other Issues

Aseptic sacroiliitis

Alternative treatment options include ultrasound-guided prolotherapy, which is an injection of saline and glucose directed to the SI joint. It is theorized that this procedure is pro-inflammatory and results in increased healing, scarring, and tightening of the SI ligaments. SI joint belts can be provided in conjunction with various therapies and, theoretically, help stabilize the gluteal muscles and support the SI joint. If the leg-length discrepancy is thought to be a major contributor, then orthotics and/or shoe lifts can be considered.

Surgical indications

• Surgery is indicated after nonoperative modalities are first attempted and exhausted.

  • Most cases (aseptic) are self-limiting and improve with rest, activity modification, and NSAIDs.
• In cases of aggressive, recalcitrant symptoms or infection, especially in the setting of a documented abscess, surgery is performed earlier in the course of treatment.

Special considerations

• Nonoperative management is the first line of treatment in the setting of pregnancy. Current evidence suggests a high likelihood of symptom resolution after childbirth.
• Sacroiliitis in the setting of a larger spondylopathy, management begins with more aggressive PT modalities, NSAIDs, and TNF alpha inhibitors.

Septic sacroiliitis

• In the setting of a high index of clinical suspicion, exam, and laboratory results (including leukocytosis), initial management includes broad-spectrum IV antibiotics, followed by culture-specific therapy, and eventually a course of PO antibiotics.
• Transitioning from broad-spectrum antibiotics to culture-specific antibiotics can occur after an adequate sample is aspirated and/or biopsied, using either interventional radiology or a surgical service if the aforementioned procedure fails. In general, an open approach for SI joint debridement and biopsy has more associated morbidity compared to the minimally invasive aspiration techniques.

Enhancing Healthcare Team Outcomes

Sacroiliitis is best managed by an interprofessional team that consists of a physical therapist, a physician, a rheumatologist, and a dietitian. Patient education is the key to good outcomes. All patients should be informed that the condition is benign and will improve with conservative measures. The patient should be encouraged to participate in a regular exercise program, lose weight, and eat a healthy diet. Home exercises can help prevent deconditioning. The patient should also be asked to quit smoking and abstain from alcohol. There is ample evidence indicating that patients who remain physically active have an excellent quality of life. [14][11]

Outcomes

The majority of patients with sacroiliitis have an excellent outcome. However, the recovery may take 2 to 4weeks. Recurrences are common if patients do not change their lifestyle. Some series report a recurrence rate of over 30%.[15][16] 

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References

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Disclosure: Benjamin Buchanan declares no relevant financial relationships with ineligible companies.

Disclosure: Matthew Varacallo declares no relevant financial relationships with ineligible companies.