Updated: 6/24/2021

Sacroiliac Joint Dysfunction

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  • summary
    • Sacroiliac Joint Dysfunction is a degenerative condition of the sacroiliac joint resulting in lower back pain.
    • Diagnosis is made clinically with pain just inferior to the posterior superior iliac spine that is made worse with hip flexion, abduction, and external rotation. 
    • Treatment is usually conservative with pain management, physical therapy, and injections. Surgical management is indicated in patients with progressive symptoms who fail nonoperative management.
  • Epidemiology
    • Incidence
      • is frequently overlooked and can explain up to 15% to 30% of cases of lower back pain in the outpatient setting
    • Risk factors
      • previous lumbar spine fusion
        • especially when there is >3 levels involved
        • considered analogous to adjacent segment disease
      • pregnancy and vaginal delivery
      • previous trauma to the pelvis
      • prior iliac crest bone graft harvesting
  • Etiology
    • Pathophysiology
      • idiopathic mechanism is the most common
        • believed to be a result of repetitive trauma to the SI joint
          • can begin insidiously or acutely
        • pain is hypothesized to be generated from
          • ligamentous/capsule tension
          • extraneous compression or shear forces
          • hypomobility or hypermobility
            • increased levels of estrogen or relaxin during third trimester of pregnancy leading to hypermobility of the SI joint
          • aberrant joint mechanics
          • myofascial or kinetic chain imbalances
          • inflammation
      • intra-articular mechanisms
        • arthritis
          • inflammation and degeneration of the SI joint
          • occurs in nearly 100% of patients with spondyloarthropathies
            • ankyklosing spondylitis
            • Reiter's syndrome
          • results in subchondral sclerosis, subchondral cyts, osteohytes, joint space narrowing, intra-articular gas and ankylosis
        • infection
          • usually the result of hematogenous spread
          • typically unilateral involvement
          • organisms:
            • Staphylococcus aureus
            • Pseudomonas aeruginosa
            • Cryptococcus organisms
            • Mycobacterium tuberculosis
          • predisposing factors:
            • immunosuppression
            • endocarditis
            • IV drug abuse
        • metabolic
          • leads to early degeneration of the joint
          • diseases:
            • calcium pyrophosphate crystal deposition
            • gout
            • ochronosis
            • hyperparathyroidism
            • renal osteodystrophy
            • acromegaly
        • tumors
          • primary
            • very rare for SI joint
            • most common types:
              • giant cell tumor
              • synovial villoadenomas
              • chondrosarcomas
          • secondary (metastatic)
            • most common
            • pelvis accounts for 40% of all oseous metastasis (2nd to spine)
      • extra-articular mechanisms
        • ethesopathy
          • inflammation of the ligamentous attachements to the SI joint
          • frequently occurs with spondyloarthropathies
          • more frequently the posterior ligaments
        • insufficency fractures
          • osteoporotic fractures in elderly patients
          • repetitive trauma in athletes and military recruits
        • post-traumatic
          • more common after lateral compression pelvic ring injuries
    • Genetics
      • HLA-B27
        • associated with ankylosing spondylitis
    • Associated conditions
      • orthopaedic conditions
        • lumbar spinal fusion
        • post-traumatic arthritis
        • metastatic tumors
      • medical conditions & comorbidities
        • anklyosing spondylitis
        • gout
        • pseudogout
        • infections
  • Anatomy
    • Osteology
      • articulation of the ilium and the sacrum
        • largest axial joint in the body
      • considered synovial even though the superior 75% is not synovial
      • joint surface area of 17.5 cm^2
      • articular surface changes with age
        • flat until puberty
        • by age 30 ridges form on the the iliac articular surface
        • synovial surface begins to erode by age 50
        • ankylosis is common in men by age 50
    • Muscles
      • gluteus maximus
        • has fibrous extensions that attach to the anterior and posterior joint capsule
        • has attachments into the sacrotuberous ligament
      • gluteus medius
      • erector spinae
      • latissimus dorsi
      • biceps femoris
        • has attachments to the sacrotuberous ligament
      • oblique and transverse abdominus
    • Ligament
      • anterior joint capsule and ligaments
        • are relatively thin
      • posterior interosseous ligament
        • forms the posterior border of the joint capsule
        • there is usually a rudimentary or absent posterior joint capsule
      • sacrotuberous ligament
        • attaches from the anterior sacrum and SI joint to the ishcial tuberosity
      • sacrospinous ligament
        • attaches from the anterior sacrum and SI joint to the ischial spine
    • Innervation
      • anterior innervation
        • L2-S2 ventral rami and sacral plexus
      • posterior innervation
        • L4-S4 dorsal rami
    • Biomechanics
      • SI joint functions as a triplanar shock absorber
        • dissipates loads of the upper trunk and faciliates parturition
        • can withstand a medial directed load six times greater than the lumbar spine
        • fails in 1/20th the axial load of the lumbar spine
        • sacral compression with weightbearing results creates "keystone in arch" effect
          • muscles with fibers perpendicular to SI joint also generate compression
      • loss of SI joint motion hinders ability to dissipate forces
      • complex motion at the SI joint:
        • gliding
        • rotation
        • tilting
        • nodding (nutation)
          • most common form of motion
          • described as the backward rotation of the ilium on the sacrum
          • counternutation is the forward rotaton of the ilium on the sacrum
        • translation
      • joint motion is limited to <4° of rotation and 1.6 mm of translation
      • motion of the joint progressively decreased with age
        • age 40-50 for men
        • greater than 50 for women
  • Presentation
    • Symptoms
      • pain patterns
        • pain usually present just inferior to the posterior superior iliac spine
          • frequent pain referral area of other spine pathologies
          • only 4% of patients will complain of pain above L5
          • can radiate past the knee and into the foot
        • wearing a tight fitting belt may improve symptoms
    • Physical exam
      • inspection
        • patients may have an antalgic gait
      • palpation
        • identify focal areas of tenderness
          • sacral sulcus (most tender location)
          • posterior superior iliac spine (second most tender location)
      • motion
        • evaluate hip and knee for underlying pathologies
      • neurovascular
        • in isolated SI joint dysfunction patients are neurovascularly intact
          • pain-inhibited weakness may be present
      • provocative tests
        • overview
          • based on a battery of tests, no single test has 100% diagnostic accuracy
          • >3 positive tests is highly suggestive of the diagnosis
        • Patrick's test (FABER)
          • also called flexion, abduction and external rotation test (FABER)
          • patient will report pain in the SI joint with this maneuver
            • groin pain suggests iliopsoas tendonitis or internal hip pathology
        • Fortin's finger test
          • considered positive if patient localizes pain twice to region inferomedial to PSIS
        • Gaenslen's test
          • performed with the affected side hip extended off examination table and unaffected side hip and knee flexed and held by patient
          • shearing across SI joint causes pain
        • SI compression test
          • performed with patient laying lateral on exam table
          • medial directed force applied over the iliac crest on the affected side
          • reproduction of pain is considered positive
        • anterior sacral thrust test
          • performed with patient positioned prone on the examination table
          • anteriorly directed force is applied to the sacrum
          • test is considered positive if pain is reproduced in the SI joint
        • SI distraction test
          • with the patient supine on the examination table a posteriorly directed force over the ASIS
          • test is considered positive when pain is reproduced in the SI joint
        • straight leg raise
          • used to detect radiculopathy due to herniated disc
          • usually negative in setting of SI joint dysfunction
          • may be positive if leg brought above 60° of elevation
          • caused by increased SI joint motion at this level of elevation
  • Imaging
    • Radiographs
      • recommended views
        • AP, lateral, internal oblique, external oblique, inlet, and outlet views of the pelvis
          • to rule out other pelvic pathology
        • flamingo views
          • indicatedwhen there is suspicion of pelvic instability
          • alternating single leg standing films of the pelvis
        • SI joint views
        • AP, lateral, flexion and extension views of the lumbar spine
          • to identify other spinal pain generators
      • findings
        • joint space narrowing
        • subchondral sclerosis
        • subchondral cysts
        • osteophytes
        • ankylosis
      • sensitivity and specificity
        • up to 25% of asymptomatic patients over the age of 50 will have abnoraml SI joints in radiographs
    • CT
      • indications
        • has poor diagnostic power compared to SI joint injections
        • deformity correction or surgical intervention is planned
      • views
        • pelvis and sacrum
          • sagittal and coronal views
          • 3D reconstructions
    • MRI
      • indications
        • done to exclude other diagnoses
        • identification of tumors, infectious process, or soft tissue components
    • Bone scan
      • indications
        • studies have reported on the predictive power of SI joint pathology with SI joint injections
      • sensitivity and specificity
        • specificity - 90%
        • sensitivity - 12%
        • positive predictive value - 86%
        • negative predictive valuae - 72%
  • Differential
    • Key differential (top 5)
      • lumbar spinal stenosis
      • degenerative disc disease
      • hip osteoarthritis
      • hip labral tear
      • lumbar disc herniation
  • Treatment
    • Nonoperative
      • oral medication, physical therapy, pelvic belt, and prolotherapy
        • indications
          • first line of treatment
        • modalities
          • oral medications
            • mainly involve NSAIDS to reduce inflammatory process associated with pain
            • opioid medications should be used sparingly
            • minimum of 4 week of non-operative modalities trial before proceeding with SI joint injection
          • physical therapy
            • +/- hot/cold therapy
            • treatment focuses on addressing core muscle strengthening, proprioception, and flexibility to correct lumbopelvic and hip biomechanics
          • pelvic belt
            • belt that applies medial directed force on greater trochanters
              • 4 to 8 inch wide belt that is applied around the greater trochanters
              • external device that mimics the function of ligaments
            • limits the motion and shear forces across the SI joint by providing compression
          • prolotherapy (controversial)
            • phenol or glucose-based solutions injected at the base of ligamentous complexes to induce scarring
            • generates inflammatory response resulting in fibroblastic migration and resultant scar that stabilizes joint
        • outcomes
          • most effective in the acute phase of pain
          • pelvic belt more effective for SI joint pain following pregnancy
          • prolotherapy more effective in the setting of ligamentous laxity
      • SI joint corticosteroid injections
        • indications
          • second line of treatment
        • outcomes
          • 60% success rate in pain relief at 6 months
            • >75% reduction in SI joint pain following a single injection is confirmatory of the diagnosis
            • >50% reduction in SI joint pain following two injections
          • lower success rate in patients with previous lumbar fusion
      • radiofrequency ablation
        • indications
          • third line of treatment
        • technique
          • targets lateral branches of the sacral nerve roots
        • outcomes
          • efficacy is limited due to the inability to denervate the anterior neural structues of the SI joint
    • Operative
      • open SI joint arthrodesis
        • indications
          • confirmed diagnosis of SI joint dysfunction as primary pain generator
          • poor response to nonoperative treatment options
          • patients with aberrant SI anatomy, sacral dysmorphism, or revision surgery
          • previously infection was the only indication for arthrodesis
        • outcomes
          • new literature with favorable outcomes in appropriately selected patients
      • minimally Invasive SI joint arthrodesis
        • indications
          • confirmed diagnosis of SI joint dysfunction as primary pain generator
          • poor response to nonoperative treatment
          • normal SI joint anatomy
        • outcomes vs. open
          • shorter hospital stay
          • smaller incision
          • theoretical decrease in surgical site infections
          • decreased limitation of postoperative weightbearing
            • quicker return to full weightbearing than open arthrodesis
          • decreased blood loss
  • Techniques
    • SI joint corticosteroid injections
      • technique
        • performed under fluoroscopy or ultrasound guidance
          • studies have shown that without imaging the injection is in the SI joint only 22% of the time
        • can be used as both a diagnostic and therapeutic injection
        • no more than 3 injections in a 6 month perior or 4 injections in 1 year
    • Radiofrequency ablation
      • technique
        • targets lateral branches of the sacral nerve roots
        • dorsal nerve ramus ablation
          • L5-S3 dorsal rami innervate SI joint
    • Open SI joint arthrodesis
      • approach
        • performed through posterior approach (anterior is limited by vital neurovascular structures)
      • technique
        • cartilage is removed and bone graft is packed into the obliterated space
        • stabilized with posterior plate and screws, iliosacral screws, or cage construct
        • made protected weight bearing for 12 weeks following surgery
    • Minimally invasive SI joint arthrodesis
      • approach
        • percutaneous placement of implants
      • technique
        • newer techniques involve triangular titanium porous coated implants
        • "fusion" occurs by bone growth onto the implant rather than direct fusion of the joint
        • requires multiple implants placed across SI joint to achieve stability
      • complications
        • patients with a dysmorphic sacrum have a higher risk of iatrogenic nerve injury
  • Complications
    • Surgical site infections
      • risk factors
        • immunocompromised
        • smoking
        • diabetes
    • Wound complications
      • risk factors
        • open surgical technique (wound is located in the dependent position)
    • Nerve injury
      • risk factors
        • minimally invasive technique
        • sacral dysmorphism
      • injury to the L5, S1, or S2 nerve roots
    • Pseudoarthrosis
      • occurs in up to 5% of cases
      • revision arthrodesis with open surgical technique
  • Prognosis
    • Natural history of disease
      • quality of life of patients with SIS is more affected than patients with chronic obstructive pulmonary disease and mild heart failure
      • equivalent to patients with hip and knee arthritis
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(SBQ18SP.26) A 70-year-old gentleman presents with left lower buttock pain 5 years after prior spine surgery as seen in Figure A. He subsequently underwent a left total hip replacement 1 year ago that relieved all of his groin pain but left lower buttock pain persists. He reports improved symptoms when he wears a tight belt. On examination, he has a negative straight leg raise, a positive FABER test, and a positive Fortin's finger test. He has an injection into the affected area with a >75% relief of symptoms. Which of the following risk factors may have predisposed him to this condition?

QID: 211388

Age >65




Male gender




Total hip replacement




Steroid injection




Spine fusion



L 2 A

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