Furthermore, no specific physical examination maneuver has truly been validated to identify sacroiliac pathology, making it even harder to study the effectiveness of treatment techniques.2
However, a thorough examination using a combination of patient history, pain patterns, multiple examination tests, and possibly intra-articular injections can often pin down the SI joint as a culprit in low-back pain. Multiple treatment options are available to address this enigma, although research is lacking comparing such options.
Targeting the SI Joint
The SI joint is the largest axial joint in the body, and is considered a synovial joint even though only a small percentage of its joint surface is synovial.2 Its inherent stability is formed by its bony morphology, as well as its fibrous capsule and strong ligaments, including the iliolumbar, sacrotuberous and sacrospinous, as well as the anterior, posterior, interosseous and accessory sacroiliac ligaments.2
It's not uncommon to be fused by the time one turns 50 years of age, and degenerative changes can often be seen radiographically.2 The stability in this region is important due to the fact that many trunk and leg muscles attach to this region of the pelvis.
The SI joint absorbs loads from the axial spine, but too much compressive load can stress the weaker anterior joint capsule and ligaments.2 Though several axes of motion occur at the SI joint, the most common type is nutation and counternutation, or backward and forward rotation of the ilium on the sacrum.2
With axial force, the strong associated muscles and ligaments produce compression and closure of the SI joint.2 Whether abnormal motion occurs and leads to dysfunction has been a heated topic of debate between spine surgeons, therapists and chiropractors, with each having varying views. Though there are many axes of motion that can occur at the SI joint, the amount of rotator motion is less than 2 degrees, and the amount of translatory motion less than 2 mm.
This has led many to believe that such a small amount of movement or asymmetries in these movements are too small to reliably assess, and this poor intertester reliability has been supported in the literature.3 Even after mobilization and manipulation of this joint, movement in this area is often unchanged.4
So if such limited motion occurs at this joint, how can pain be generated? The most common cause of SI dysfunction is idiopathic, with a specific event or cumulative trauma to the area.2 The actual site of pain generation has been debated, and theories vary from ligamentous or capsular tension, hypomobility or hypermobility, synovitis or joint damage.2
Pain may specifically arise from within the joint in such diseases as arthritis or infection.2 Inflammatory disorders can cause SI pathology, such as ankylosing spondylitis-in fact, SI joint dysfunction is needed for the basis of diagnosis of ankylosing spondylitis. Pregnancy can elevate relaxin and estrogen levels, causing hypermobility in all joints, including those at the pelvis, specifically late in the pregnancy period.2
Identifying SI Dysfunction
Pain in the region inferior to the posterior superior iliac spine (PSIS) is the pain pattern for SI joint pathology. However, it's also a common area for that referred from spinal pathology.2,5,6
Slipman et al used intra-articular injections to assess SI joint pain referral zones, and found that 94 percent had pain in the ipsilateral buttock with the injection.5
However, surprisingly almost 50 percent also had pain in the thigh, and over one quarter of the subjects had pain down into the lower leg.6
Though it's been proven that very limited motion occurs at the SI joint, there are varying camps of thought on whether abnormalities of this motion can be accurately assessed. A survey of 186 Washington State therapists demonstrated that 75 percent of them use screening tests for SI function whenever they are evaluating a patient with low back pain.1,7
Numerous tests have been advocated for the assessment of SI joint mobility, but again one must use them with the acknowledgement that the intertester reliability of such tests is still in question, and that the relationship of asymmetries with pain or pathology has yet to be truly borne out in the literature.
As with any examination, begin with inspection and palpation. Assess for tenderness in the sacral sulcus, which is the region just medial to the PSIS.2,8 A thorough spine and hip evaluation should be performed, including a complete neurological examination. Patients with SI joint dysfunction should have a normal neurologic exam; however, they may have pain with SLR testing when the leg is elevated above 60 degrees.2 The validity to identify SI dysfunction through special tests has not been substantiated in the literature, but are still commonly used.
Flexion test. The flexion test can be done either in the sitting or standing position. The examiner palpates the patient's PSISs and then asks the patient to flex forward at the waist. The examiner is watching for any asymmetries from side to side at the PSISs as the patient flexes forward. If one moves more cranially than the other, this would indicate decreased mobility of the ilium on the sacrum.
Standing Gillet test (Stork test). To test the right SI joint, palpate the right PSIS with the right thumb, and place the left thumb over the midline of the sacrum at the same level. With patient standing, they're asked to flex the right hip up slowly past 90 degrees while the clinician examines the PSIS motion. A negative test is when the PSIS moves caudally, while a positive test occurs if the PSIS does not move or moves cranially. This test assesses movement of the innominate bone's posterior movement on the sacrum; in other words, its ability to move with the sacrum when it posteriorly tilts.
Supine long sitting test. With the patient supine, the examiner checks leg lengths via palpation of the medial malleoli, and then asks the patient to flex up to long sitting while assessing leg lengths. If the right leg is shorter in supine, but then apparently lengthens in sitting, it could indicate a posteriorly rotated innominate.
Prone knee flexion test. This test also assesses leg length differences to determine whether apparent leg length inequalities are coming from the SI joint. Apparent leg lengths are tested in prone position with the knees fully extended, then flexed to 90 degrees. Again, a finding of a shorter leg with the knees extended would suggest a posteriorly rotated innominate.
Deeper Investigations
The intertester reliability for the above four tests are only 24 to 50 percent between therapists.1,3 Some feel that combining several special tests can improve the ability to pick up on SI joint dysfunction. However, studies based on patients with proven SI dysfunction have yet to be completed.1,9
Also, these special tests assess for asymmetries in the pelvis, but the clinical relevance of such asymmetries and its relationship to pain or pathology has yet to be proven. Even when looking at X-rays of asymptomatic patients, you can see many asymmetries in the spine and pelvis; they don't necessarily equate to pathology.
Pain provocation tests don't assess SI mobility as much as they attempt to differentiate the source of pain by trying to stress the SI joint. These tests have been found to have a higher intertester agreement than those described to assess SI joint mobility.1,3
Iliac compression test. With the patient side-lying, a downward force is given to the patient's upper iliac crest in the attempt to elicit pain.
Iliac gapping test. With the patient supine, the examiner crosses their arms to elicit a downward and outward or lateral force to the inner aspect of the patient's ASIS.
Should either of these tests elicit lower back and buttock pain, how do you go about proving that it's coming from the SI joint? Currently, the gold standard is diagnostic injection into the SI joint.
Most studies use relief of greater than 75 percent from such an injection as diagnostic, with 50 to 75 percent being equivocal.2 In the perfect world for research criteria, one would also have negative facet joint block and discograms, as well as a control injection such as saline, into the SI joint. For obvious reasons, including patient risk and cost, this isn't done. However, repeat injections have been attempted to decrease the risk of false positive tests.
Though SI joint injections remain the gold standard, they're still far from perfect. First, the anesthetic injection has the ability to leak to other areas around the SI joint, which can give false positive results. Also complicating the picture is the theory that SI dysfunction pain may not only be due to intra-articular pathology, which could cause false negative tests. Some theorize that pain may be coming from overstrained ligaments, muscles or other structures near this region.
Maigne et al used a short-acting anesthetic to perform screening blocks on patients with unilateral pain in the area of the PSIS to evaluate the effectiveness of various pain provocation tests.10
Patients were diagnosed with SI joint pain only if the first shot and one shot a week later gave greater than 75 percent relief, of which 18.5 percent of patients were diagnosed with such dysfunction.10 These authors found no relationship between pain provocation tests and those diagnosed with SI dysfunction via screening blocks.
Treating SI Dysfunction
A variety of treatment techniques have been devised to address SI joint dysfunction. Treatment modalities have included education, exercise, bracing, manual therapy, mobilization, manipulation, medication and injection, as well as surgical stabilization. The difficulty in truly discerning SI joint pathology from lumbar pain has been a major limiting factor in analyzing the efficacy of various treatment techniques.
As with any diagnosis, the initial basis of treatment should be aimed at conservative measures and restoring the patient's functional mobility.
Anti-inflammatory medications can be used initially to decrease pain and inflammation. Specific flexibility, conditioning and strength deficits should be addressed with a focus on independent home exercise programs.
Bracing may be used for pain relief, specifically when suspecting hypermobility at the SI joint. Often a trial in the office can be given using a gait belt to see a patient's response, and if positive, specific SI belts can be purchased for the patient. Manual techniques can be broken up into direct mobilization, direct manipulation, and indirect techniques, such as muscle energy.2
Only when all conservative measures have been exhausted do invasive procedures become an option. Intra-articular or extra-articular SI joint injections can be performed using an anesthetic and corticosteroid to reduce pain and inflammation.
Prolotherapy is an alternative treatment that involves injecting an irritant substance (dextrose/glycerine/phenol) into a ligament or tendon to promote an inflammatory response. It's aimed more at chronic issues, in which one is trying to restart a localized acute inflammatory healing phase to lay down new collagen production.
When less invasive techniques have failed, patients may consider radiofrequency ablation as a salvage procedure. Radiofrequency denervation for the SI joint is aimed at the L5 dorsal ramus and the lateral branches of the S1-3 dorsal rami.2 Surgical procedures, including SI joint fusions, are rarely indicated and only small case series have been reported.2
Sacroiliac dysfunction has remained an enigma due to the difficulty in diagnosing and reliably differentiating it from lumbar spine pathology. Special tests to provoke SI pathology have been proven to have only varying levels of sensitivity and specificity.
One must rely on a thorough history, physical exam and pain pattern to help differentiate SI joint pain from lumbar pathology. Unilateral buttock pain with palpable tenderness at and medial to the PSIS in the region of the sacral sulcus has been found to be the most sensitive sign for SI joint dysfunction.
Diagnostic injections are still the gold standard when trying to differentiate SI joint pain from lumbar pathology. Despite the difficulty in accurately diagnosing SI dysfunction, various treatment techniques have been devised to focus on SI joint pathology.
A treatment approach aimed at SI joint pathology can also be used to help differentiate SI pathology from that of the spine. Continued research is needed in this area to help guide our diagnostic examinations as well as our treatment regimens for SI joint dysfunction.
Jeremy Bruce is an orthopedic surgery resident at the University of Tennessee-Chattanooga.