Continuing Education Activity

Sacroiliac joint injury is a common type of low back pain. Differentiating SI joint pain from mechanical low back pain is essential. This activity outlines the evaluation and management of sacroiliac joint injury and highlights the role of the interprofessional team.

Objectives:

• Identify the etiology of sacroiliac joint injury medical conditions and emergencies.
• Review the appropriate evaluation of sacroiliac joint injury.
• Outline the management options available for sacroiliac joint injury.
• Describe the interprofessional team strategies for improving care coordination and communication to advance sacroiliac joint injury and improve outcomes.

Introduction

Sacroiliac (SI) joint injury is a common cause of low back pain. Posterior pelvic joint pain a common name for SI joint dysfunction. The spine and pelvis are connected by the sacroiliac joint. The SI joint lies between the iliac's articular surface and the sacral auricular surface. When an injury occurs to the SI joint, patients often experience significant pain in their low back and buttock region. The SI joint experiences forces of shearing, torsion, rotation, and tension. Ambulation is heavily influenced by the SI joint, as this is the only orthopedic joint connecting our upper body to our lower body. The joint is a relatively stiff synovial joint filled with synovial fluid. The bones of the sacrum and ilium are coated in hyaline cartilage at their articular surfaces with dense fibrous tissue connecting the ilium and the sacrum. SI joints typically only have a few degrees of motion.

Diagnosing sacroiliac (SI) joint pathology can be challenging. One of the difficulties providers can run into in the evaluation of SI joint injury is in distinguishing between lower lumbar pain (lumbago) from SI joint pain. Specialized tests can be instrumental in making this distinction. It is vital to keep SI joint pain as part of the differential diagnosis of low back pain, with up to 30% of low back pain secondary to the SI joint.[1] Pregnant women experience joint laxity due to hormonal changes, and this is when the SI joint is the most vulnerable to injury. Between the ages 40 and 50, the SI joint fuses decreasing the SI joints' laxity. Fusion and or pregnancy may lead to hypermobility or hypomobility, which may exacerbate SI joint pain. Osteoarthritis is a common cause of SI joint pain.[2][3]

However, there are multiple etiologies and a variety of factors that can contribute to SI joint injury.[3] The overlap in symptoms with various causes of low back pain, as well as the numerous origins of SI joint dysfunction, make it not only a tough diagnose to make but also challenging to treat.[2][3] SI joint injury can be acute but becomes chronic after three months of persistent pain. Chronic SI joint pain occurs when the free nerve endings within the SI joint degenerate or become chronically activated. Pain can be constant or intermittent for SI joint injury. Given the prevalence of mechanical back pain, it is essential to rule out or exclude a lumbar origin of suspected SI joint pain before diagnosis. It is often hard to pinpoint in which cases SI joint dysfunction is the primary reason behind a patient's back pain. Some exceptions include trauma and pregnancy.  

Extra joint mobility of the joint can result in pain in SI joint injury. However, hypomobility is a hallmark of ankylosing spondylitis, a common cause of inflammatory sacroiliac injury. SI joint dysfunction often occurs in unison with mechanical back pain. The sacroiliac joint may also be the site of pain referred from the lumbar vertebra rather than the origin of the patient's pain. For example, degenerative disc disease at the L5-S1 vertebrae may become interpreted at the SI joint, but the source is much higher in the lumbar spine. There are multiple patterns of referral of pain for patients with SI joint injury. Including, the posterior thigh, knee, or foot. The most common site of pain referral is the posterior thigh, seen in 50% of patients.[4][5][6] Complicating SI joint injury management further is a lack of clearly defined guidelines in the diagnosis and management of SI joint pain. MRI is the test of choice in the evaluation of SI joint dysfunction. Furthermore, radiographic-guided anesthetic injection provides a reliable way of determining SI joint pain in many cases.

The sacroiliac joint is a commonly targeted area of treatment of chronic low back pain as well.[7][8] Conservative treatment options for SI joint injury often include physical therapy, home exercises, over the counter pain medication such as NSAIDs or acetaminophen. When conservative management fails, corticosteroid injections and radiofrequency ablative therapies are viable treatment options. In severe, refractory cases, surgery can fuse the SI joint. Patient education is essential in SI joint injury, including posture, proper lifting technique, stretching, and regular exercise. Weight loss helps SI joint pain, as well.

Etiology

Injuries to the sacroiliac joint can occur from various etiologies. 88% of cases of SI joint injury are due to either repetitive microtrauma or acute trauma. There is a high prevalence of SI joint injury in athletes. Separately, 20% of cases are pregnancy-related, while 4% are idiopathic.[9] Trauma in the context of pelvic ring injuries is one example of SI joint injury. Pelvic ring traumatic injuries include three main categories, including anteroposterior compression, lateral compression, and vertical shear-type injuries. Furthermore, injuries to the sacroiliac joint include incomplete SI dislocations, complete SI dislocations, and SI fracture-dislocations.

There are also three types of fractures associated with SI joint injury. A type one fracture is a minor fracture of the anterior aspect of the S2 foramen. This fracture creates a large crescent-shaped fragment that is stable. Less than one-third of the SI joint is involved, and the fracture encompasses the least amount of ligament injury of the three types of fractures. Separately, a type two fractures occur between the anterior aspect of the S1 and S2 foramen. The fracture creates a smaller crescent-shaped fragment compared to the type one injury. Type two fractures occur when one-third to two-thirds of the SI joint is involved. Lastly, a type three fracture encompasses the superior and posterior aspects of the SI joint up to the S1 nerve root. Greater than two-thirds of the sacroiliac joint are involved and include a higher degree of ligament disruption. However, the fracture is typically smaller than a type one or type two fracture. A posterior fracture-dislocation of the SI joint involves variable disruption of the SI ligament complex.[10]

The L5 nerve root crosses the sacral ala 2 cm medial to the SI joint. In the case of injury, the nerve root can be involved causing radicular pain. SI joint innervation occurs via the ventral rami of the L4 and L5 vertebra, as well as the dorsal rami of L5-S2, and the superior gluteal nerve. Injury to these nerves can cause neuropathic SI joint pain. Generalized gluteal pain can be secondary to an injury of the SI joint or local nerves surrounding the SI joint, causing radiculopathy. When the S1 nerve root is directly injured during SI joint injury, it can also create radiculopathy.

Separately, during pregnancy, laxity occurs within many of the joints in the pelvis. The hormone relaxin causes joint mobility during pregnancy. As the pelvis widens during pregnancy, the SI joint becomes more mobile. The expecting mother can experience SI joint pain as the hips rotate, putting stress on the SI joint. Pain can be both unilateral or bilateral during pregnancy.[11][12] SI joint pain during pregnancy is a component of pelvic girdle pain. Patients who experience pelvic girdle pain during pregnancy have high rates of disability than patients suffering mechanical back pain.[13] Risk factors for SI joint dysfunction during pregnancy include forceps delivery, intense contractions, fetal macrosomia. Multiparity, precipitous labor, and a rapid second stage of labor also contribute.[14][15][16][9]

Anatomical variations can lead to SI joint injury as well. An increase in lumbar lordosis, as well as an anterior tilt to the pelvis, can lead to SI joint dysfunction.[17] Patients with underdeveloped musculature can develop postural imbalances, such as a short leg.

Osteoarthritis also plays a role in the development of SI joint pain. Typical of all osteoarthritic joints, joint space narrowing, osteophyte formation, and sclerosis of the SI joint can be seen on x-ray.

Furthermore, inflammatory arthritis can cause SI joint injury. Ankylosing spondylitis is the most common type of inflammatory arthritis of the SI joint. Erosion of the joint can occur over time, leading to disabling pain. Subchondral edema is the earliest sign of sacroiliitis on imaging. Ankylosing spondylitis causes bony erosions of the SI joint. As decay occurs, the joint space widens and becomes sclerotic. Over time the joint fuses as erosion occur across the entire joint.[18] The severity of deterioration is from zero to four grade. Zero being normal, and full fusion of the joint.[19] Higher rates of progression of SI joint injury include active inflammation of the SI joint seen with elevated CRP or on MRI, history of smoking, male sex, and HLA-27 positive testing.

Epidemiology

13% of patients with chronic low back pain have SI joint dysfunction.[20] Between 15 and 30% of low back pain can be attributed to SI joint injury.[20][10]

Lateral compression of the SI joint comprises up to 80% of pelvic rim injuries. Crescent fracture-dislocations of SIJ accounts for 12% of pelvis ring injuries.[10] 

The prevalence of abnormal SI joint movement is 20% in college students and between eight to 16% in asymptomatic individuals.[20] 

Over 80% of patients report clinically significant pain improvement following surgical fusion of the SI joint compared to 25% in the nonoperative group. 3% of patients who undergo fusion surgery require surgical revision. Operative therapy typically requires a 75% improvement following an SI joint diagnostic injection before surgery.[21][22]

History and Physical

The history provided for SI joint pain may look very similar to mechanical back pain, with a few exceptions. Pain is usually localized to the buttock region and may occur with the sensations of numbness, tingling, weakness, pelvic pain, leg instability, and groin pain. The patient often points to the area between their gluteal folds and posterior iliac crests.[23] Walking up and down a flight of stairs, sitting cross-legged, or prolonged sitting or standing may exacerbate symptoms. In an acute injury, pain can be stabbing in nature. Patients often complain they cannot sleep on the affected side of SI joint pain. Pain can also be worse with menstruation. 

Radiation is pervasive in SI joint injury seen in up to 50% of cases, the majority into the lower extremity.[24][25] There are multiple patterns of referral of pain for patients with SI joint injury. Including, the posterior thigh, knee, or foot. Pain in the SI joint often refers to the gluteus muscles and can also radiate into the groin, mimicking hip pain. The most common area of referred pain in cases of SI joint injury is the posterior thigh seen in 50% of patients.[26]

The history of SI joint injury may suggest S1 radiculopathy classically seen in sciatica. Symptoms are reproducible in an SI joint neuropathy of the S1 nerve root. In cases of neuropathic pain, the patient may endorse numbness, tingling burning pain of the posterior leg extending below the knee into the plantar aspect of the foot. The patient may support sensation changes or muscle weakness, depending on the nerve root involved.

A physical exam includes a full musculoskeletal and neurologic exam of the lumbar spine, and bilateral lower extremities are a part of the SI joint injury evaluation. A complete neurological and musculoskeletal exam of the lower extremity should be mostly normal, with muscle strength, sensation, and deep tendon reflexes intact. However, Pelvic asymmetry may be appreciated on the exam. The range of motion testing of the lower extremity is a must for the assessment of SI joint dysfunction. A rectal exam may also be indicated in specific cases. On physical exam, there can be tenderness to the pelvic floor muscles.[27] Furthermore, tenderness along the sacral dimple (the long dorsal ligament) may also be tender to palpation in SI joint dysfunction. 

Sacroiliac joint mobility has been studied, along with the symmetry of the pelvis. Both tests are unreliable in the diagnosis of SI joint dysfunction. The compression of the iliac crest on the side of the patient's pain may reproduce symptoms.[28][29][30] If less pain is elicited during pelvic compression, this points away from lumbar pain and is more suggestive of SI joint injury. In the case of SI joint neuropathy, S1 deep tendon reflexes can be lost, there may be diminished sensation along the S1 dermatome, and the patient may even experience weakness in knee extension and flexion in more severe cases.

Special tests are often utilized in cases of suspected SI joint injury. The Gaenslen test is a special test that can be used to isolate the sacroiliac joint. The patient should be placed in the supine position; their hip flexed to their chest. The provider applies a force to the knee of the flexed hip anteriorly on the ipsilateral side of pain. Simultaneously, the contralateral knee is pushed downward; their opposite leg is allowed to fall off the table. Both SI joints are tested simultaneously. Gaenslen is considered a provocative test, reproducing the patient's symptoms.[31] The supine hip posterior thrust test is another test often used in the assessment of SI joint injury, where pressure is applied to the femur. Trendelenburg testing can help determine if gluteus medius weakness is contributing to SI joint pain. Pain over the contralateral sacroiliac joint during the FABER test is a positive finding for SI joint pathology. When there are three or more provocation tests of SI joint pathology that are positive, the tests have 91 and 78%, sensitivity and specificity, respectively, for SI joint injury. Specificity increases to 87% in the patients who deny midline spine pain.[32]

Evaluation

X-ray is often the first test utilized in SI joint injury. Weight-bearing anteroposterior views are usually all that is needed for the initial radiographic assessment of SI joint pain.[33][34] Radiographs, including AP, inlet, and outlet views, can also be obtained. Sacroiliac views at 25 to 30-degrees of rotation when suspicion is high is also an option when there are nondiagnostic initial x-rays. What is an abnormal X-ray of the SI joint? A standard distance between the sacrum and the ilium is 4 to 5 mm. Narrowing of the joint often leads to injury: joint space narrowing or sclerotic erosion of the joint space are often seen on X-ray. Grade one or two SI radiographs for sacroiliitis have high variability. Thus normal X-rays can be interpreted as SI joint dysfunction.[35][36][19] Twenty to 30% of patients with a seronegative spondyloarthropathy have abnormal X-rays.[18][37][38] MRI is critical in the diagnosis of SI joint injury.[39] Although MRI is the best test for the SI joint injury assessment, it does have a significant false-positive rate in healthy patients.[40]. MRI is usually done without contrast [41]. Findings associated with sacroiliitis, such as bone marrow edema, are seen in over 20% of patients with mechanical back pain on MRI.[42][43][44] Similarly, structural changes, such as erosion of the joint, can be due to various pathologies.[45][46] Scintigraphy can also be used when there is a nondiagnostic MRI.

CT is utilized when MRI is contraindicated or unavailable. Separately, CT of the pelvis with contrast evaluates for vascular and urogenital injures. CT is more sensitive than radiograph but inferior to MRI in detecting SI joint injury.[35] CT is not generally recommended to establish the diagnosis of sacroiliitis unless MRI is contraindicated.[47] However, a low radiation CT is adequate when utilized.[35]

Local anesthetic blocks are a more invasive way to test SI joint pathology when the diagnosis is in question. An ultrasound or fluoroscopy-guided diagnostic injection assesses patient pain before the injection and directly following the injection allowing the physician to see if the pain was alleviated momentarily with short-acting anesthetics. A 75% reduction in pain is suggestive of SI joint pain. Patients who could benefit from an ultrasound-guided diagnostic injection include patients experiencing isolated SI joint pain or pain that is reproducible on three provocative tests.[48][49]

Labs are a part of the assessment for possible inflammatory SI joint injury. When sacroiliitis is seen on pelvic x-ray, a CBC, CRP, and ESR are often part of the workup.

Treatment / Management

Treatment can vary significantly between cases. For example, pregnancy-related SI joint pain often resolved in the months following delivery, while traumatic SI joint injury may require prompt surgical repair.

In acute injury ice, non-steroidal anti-inflammatory should be a part of management unless they are otherwise contraindicated. Muscle relaxers can also be used for SI joint injury such as cyclobenzaprine if the suspected injury is secondary to muscle spasm. Inflammatory sacroiliitis can be treated with TNF inhibitors as well, such as infliximab or etanercept. Weak core muscles, such as oblique muscles can contribute to injury as well. Strengthening of the transverses abdominis, as well as the obliques either through a home exercise program or physical therapy, can help improve SI joint pain. Girdles and braces also help support the core in SI joint dysfunction. Braces have been shown to reduce SI joint pain. Separately, belts can limit the motion of the SI joint. However, limited studies support its clinical significance in SI joint injury.[50][51] Home exercise programs are a more effective initial treatment for SI joint injuries compared to SI joint belts. Manipulation is a possible treatment option, but limited studies assess the clinical effectiveness in SI joint injury.[52] Numerous studies have reviewed the effectiveness of exercise, physical therapy, and stretching in SI joint dysfunction. Neuromuscular proprioceptive training and conditioning studies have also been studied. Generally speaking, physical therapy, home exercise programs, and stretching, as well as a dose of patience and time, will resolve most cases of SI joint pain.[53][54][55][56]

The effectiveness of corticosteroid injections into the periarticular surface of the SI joint is controversial at best.[2][3] Periarticular steroid injection of the SI joints can be done with and without ultrasound guidance in the case of SI joint pain unresponsive to conservative management. However, ultrasound-guided SI joint injections have increased efficiency compared to blind injections.[57] Periarticular steroid injection is superior to lidocaine injections.[57] There are limited studies completed on SI joint corticosteroid injections compared to sham injection. Fluoroscopically guided injections of the sacroiliac joint have had mixed results in terms of diagnosis and management as well.[29][58] Corticosteroid injections of the SI joint can be therapeutic in chronic cases of SI joint osteoarthritis. It is not recommended to do more than three corticosteroid injections should in a year. Cooled radiofrequency neurotomy has better pain relief compared to intraarticular SI joint injections.[3] 

 Radiofrequency denervation is a possible treatment option for refractory, chronic SI joint pain. Rhizotomy (radiofrequency denervation) is often complete after failed corticosteroid injections.[32] However, results are mixed on its efficacy. Consensus shows a likely short-term benefit in the reduction of pain with rhizotomy that reduces over time. High-quality randomized trials are limited. The studies that have been done have limited patient size.[59]

Interestingly at both three to six months, follow-up radiofrequency ablation was shown to have a clinically significant reduction in pain and improvement of function in patients with SI joint injury in one study.[60] It is unclear if one ablative technique is superior to another for SI joint nerve ablation. Radiofrequency ablation is effective without first performing a diagnostic block for SI joint injury.[61] In a study of 228 patients unresponsive to conservative management, radiofrequency ablation was an effective treatment modality, with statistically significant improvement of pain compared to placebo at three months follow up. Yet these results were not considered clinically significant.[62] Spinal cord stimulators implanted into the sacrum can also be used to reduce SI joint pain in chronic reoccurring cases. When all else fails, surgical fusion can be done. 80% of patients endorsed clinically significant pain improvement following surgical fusion. Before surgery, it is required to have a significant improvement of pain following a diagnostic injection.[21][22]

Differential Diagnosis

Common causes of SI joint injury include pregnancy, traumas such as hip fractures, hypermobility, hypomobility, leg length discrepancies, obesity, and surgeries such as lumbar fusion. The differential diagnosis of sacroiliac joint injury includes synovitis, capsulitis, and enthesitis, infection, piriformis syndrome. Osteitis condensins ilii, and malignancies such as multiple myeloma are also a part of the differential. Functional causes can occur with scoliosis or short legs. Posterior sacral ligaments tears can cause pain in SI joint injury.[63][64] Degenerative and mechanical changes also cause SI joint pain. As osteoarthritis develops within the SI joint, causing joint space narrowing. Joint space narrow becomes a source of pain in SI joint dysfunction.

Furthermore, hip osteoarthritis should be considered in addition to SI joint osteoarthritis for low back pain and pelvic pain.[65] Inflammatory arthropathies are various and outside the scope of this article. However, they are a part of the differential diagnosis in SI joint injury. Reactive arthritis and psoriatic arthritis are a few other types of inflammatory arthropathies leading to SI joint injury not mentioned previously. Bechet disease, hyperparathyroidism can also lead to sacroiliitis.[66][67][68] Lastly, disc herniation, lumbar spinal stenosis, and mechanical back pain are part of the differential diagnosis for SI joint injury.

Prognosis

Similar to mechanical back pain, the vast majority of cases of SI joint injury improve with conservative management. Over 75% of cases respond to conservative management and physical therapy.[69] Atraumatic causes of SI joint injury tend to complete the resolution of symptoms compared to traumatic occurrences. Sedentary behavior has worse outcomes.[70][71] Physically active patients have an excellent quality of life with SI joint injury.[72] Stabilization training has been shown to cause a 50% reduction in disability, long term for SI joint injury.[73] The mean duration of symptoms in chronic SI joint injury is 43 months.[23] In cases of chronic refractory SI joint pain, 2% of patients require operative fusion. Progression of SI joint deterioration in sacroiliitis is one to 5% per year.[24]

Complications

The recurrence rate of SI joint injury in over 30% of chronic cases.[74][75] Complications often including difficulty with ambulation, chronic pain, disability, reduction of quality of life. As in the case of most musculoskeletal injuries, acute dysfunction should be treated promptly to avoid the development of chronic pain. The complications of chronic pain include significant morbidity and mortality to the patient as well as the development of opioid dependence. A lack of prompt assessment of assessment and workup of sacroiliitis can lead to significant systemic injuries.

Consultations

Physicians who specialize in diagnosing and managing pain through a comprehensive understanding of the body's mechanics and musculoskeletal system are the following: Physical medicine and rehabilitation, sports medicine, pain management, and interventional spine physicians.

Deterrence and Patient Education

Part of the initial workup for acute back pain includes an assessment of the SI joint. SI joint pain is a common type of low back pain, and it is separate from the lumbar spine or paraspinal muscles often associated with low back pain. The spine and pelvis are connected posteriorly by the sacroiliac joint. The SI joint lies between the iliac bone and the sacrum. A common cause of SI joint injury includes trauma. Trauma can be repetitive, causing a series of small injuries that accumulate over time, such as in the case of an athlete, or can be significant trauma such as a pelvic fracture from a motor vehicle accident. Separately, SI joint injury is prevalent in pregnancy.

Furthermore, SI joint pain often occurs due to arthritis. Both degenerative osteoarthritis and inflammatory arthritis can lead to SI joint injury. Inflammatory arthritis of the SI joint is commonly known as sacroiliitis. When inflammatory changes are seen on imaging may be the sign of systemic disease. Imaging for SI joint dysfunction often includes an X-ray or MRI. Most cases of SI joint injury respond to conservative management, including physical therapy. However, some cases can require corticosteroid injections or even surgical repair.

Enhancing Healthcare Team Outcomes

Managing sacroiliac joint injury can be challenging. Low back pain secondary to SI joint dysfunction requires an interprofessional team of healthcare professionals that includes a primary care provider, physical therapist, primary care sports medicine specialist, pain medicine physician, radiologist, orthopedic surgeon, nurse specialist, and in cases of sacroiliitis, a rheumatologist. Without proper management, the morbidity associated with SI joint injury can become a chronic and debilitating injury. There are multiple steps involved in the injury assessment of the sacroiliac joint, the evaluation of the underlying injury, and treatment of sacroiliac injury:

• History and physical should be complete by the primary care provider, including special physical exam tests as well as initial x-ray imaging.
• Imaging to be interpreted by the radiologist. Standard imaging includes a weight-bearing AP view of the SI joint, MRI of the pelvis and sacrum, or CT of the pelvis.
• Initial therapy often provided by the primary care provider or orthopedist includes home exercise programs, over-the-counter pain medications, bracing, belts, manipulative therapy, and physical therapy.
• The physical therapist is crucial in the strengthening of the core muscles as well as the gluteus muscles, which are needed to help support the SI joint.
• Corticosteroid injection or anesthetic injections can be done either via ultrasound or fluoroscopy injections. A primary care sports medicine physician or pain medicine specialist is often utilized for this procedure.
• Refractory treatment such as radiofrequency ablation or rhizotomy can be complete with a pain medicine specialist as well.
• Suspected inflammatory SI Joint injury usually requires further assessment, including labs and management by a rheumatologist.
• Surgery can be necessary in refractory cases. Either an orthopedic surgeon specializing in spinal surgery or a neurosurgeon often performs the procedure. 
• Many cases of SI joint injury occur in athletes. A sports medicine specialist best manages long-term treatment and management of SI joint injuries.

The management of a sacroiliac joint injury can be both acute and chronic. Treatments range from conservative management to surgery. Diagnosis requires a high index of suspension in suspected cases. However, most cases improve conservatively. Many cases require the time and effort of multiple healthcare providers. [Level 5]