Sacroiliac Joint Pain

Etiology

The potential causes of sacroiliac joint pain can either traumatic or atraumatic[2]. 

The traumatic causes of pain are:

1. Pelvic ring fractures,
2. Soft tissue injury from fall onto the buttock
3. Indirect injury from motor vehicle collision and
4. Sudden / repeated heavy lifting/strain or torsion  

The atraumatic causes of sacroiliac joint pain are:

1. Spondyloarthropathy
2. Enthesopathy
3. Osteoarthritis
4. Infection
5. Previous lumbar fusion
6. Pregnancy
7. Leg length discrepancy and
8. Scoliosis.

Repetitive shear and torsional forces may arise from various sports like figure skating, golf, and bowling[3]. Pregnancy causes sacroiliac joint pain from weight gain, increased lumbar lordosis, hormone-induced laxity in the third trimester, and the trauma associated with delivery[1]. Rear-end collisions cause sacroiliac joint injury from an indirect torsional strain on the joint. As the body is thrown forward on impact, a torsional strain acts on the sacroiliac joint of the leg that is fixed to one of the foot pedals[4].  Previous spinal surgery is a poorly recognized cause of sacroiliac joint dysfunction. Finite element analysis show increased stresses that occur at the sacroiliac joint following fusion surgery[5]. Results from the study by Ha and co-workers[6] showed a two-fold increase in sacroiliac joint degeneration following fusion as compared to controls.

Epidemiology

The lifetime prevalence of low back pain is 85% [7]. In 25% of these patients, the sacroiliac joint may be the cause of the pain.  The majority of SI joint pathologies affect the adult patient population. However, there is a bimodal distribution with two peaks—younger adults following sporting injury and pregnancy and older adults from degeneration.  Both genders and people of all races present with sacroiliac joint dysfunction.

Pathophysiology

The sacroiliac joints are usually considered as synovial joints but can also be classified as a diarthrosis-amphiarthrosis joint. The superior and dorsal portion of the joint is an amphiarthrosis. In this portion, fibrocartilage fills the joint space. The joint's inferior and ventral portion is a diarthrosis with hyaline cartilage covering the joint surfaces and possesses a synovial cavity[8]. The sacroiliac joint is the largest joint in the body, with a surface area of approximately 17.5 cms. This joint is relatively immobile, and its primary function is to transfer weight to and from the lower limbs to the axial skeleton. There are three large lever arms, the trunk, and the lower limbs whose movements transmit significant force through the sacroiliac joint. The bony contours and the strong interconnecting ligaments allow only minimal motion at the joint surfaces[9].

Anterior innervation of the sacroiliac joint is from the ventral rami of the L5 to S2 nerve roots. The lateral branches of the dorsal rami of the S1 to S4 nerve roots innervate the posterior part[10]. Immunohistological studies have demonstrated nociceptors throughout the joint capsule, ligaments, and subchondral bone[11]. An injury or inflammation in any of these structures can potentially cause pain.

History and Physical

Sacroiliac joint pain can arise from a variety of clinical conditions. A thorough history of clinical symptoms and past medical conditions should be a routine part of the comprehensive evaluation of a patient presenting with SI joint disorders.

Patients usually complain of deep-seated pain, which extends down the posterior thigh and up to the knee. Pain can frequently mimic and be misdiagnosed as radicular pain. Patients are also likely to complain of pain while sitting down, lying on the ipsilateral side or when climbing stairs. Pain from the sacroiliac joint usually follows an inciting event and does not arise insidiously[12]. The inciting event helps to differentiate between pain arising from the sacroiliac joint and pain arising from the facet joints or the disc. Facetogenic or discogenic pain tends to be of insidious onset, whereas patients with sacroiliac joint dysfunction can identify a precipitating event. The usual precipitating events are motor vehicle collisions, falls, repetitive stress, or pregnancy.

Patients with isolated SI joint dysfunction often localize their pain inferior and medial to the PSIS. Pointing the finger to this area is the Fortin finger test[13]. Localized pain is not always a reliable presentation, as a 2000 study reported 18 different pain referral patterns from the SI joint. Among these other patterns included pain down the posterior/lateral thigh (50%), pain distal to the knee (28%), and pain in the foot (14%)[14].

A comprehensive physical examination should consider alternate pathology in the thoracolumbar spine, pelvic organs, or hip that could refer pain to the posterior hip region. Test the range of movement and tenderness in these areas. Perform a neurological examination encompassing sensory (pinprick and light touch), motor power, deep tendon reflexes, and Babinski on both lower limbs. Leg length should be measured as unequal leg lengths can lead to sacroiliac joint dysfunction.

Numerous stress tests to identify sacroiliac joint dysfunction are available. Unfortunately, there is no single test that is both sensitive and specific in identifying sacroiliac joint dysfunction. A few of these maneuvers are

Patrick's or FABER's (flexion, abduction, and external rotation) test[15]

The patient lies supine on the exam table. Flex and externally rotate the hip and knee of one leg to rest the lateral malleolus just proximal to the contralateral patella. Pain in the sacroiliac joint region is considered positive for sacroiliac joint dysfunction. Pain in the hip or groin suggests hip pathology.

Gaenslen's test[16]

The patient lies supine on the exam table. Flex the contralateral hip and knee towards the patient's chest while the opposite leg is allowed to drop off the table's side. Pain in the sacroiliac joint region of the lowered leg suggests sacroiliac joint dysfunction.

Distraction test[16]

The patient lies supine on the exam table. The examiner applies outward rotatory stress on both the anterior superior iliac spines. Pain in the sacroiliac joint region is suggestive of sacroiliac joint dysfunction.

Thigh thrust[16]

The patient lies supine on the exam table. The examiner flexes the hip and knee on one side till the thigh is vertical to the exam table. The examiner wraps an arm around the flexed thigh and knee and provides a posteriorly directed force. The opposite hand of the examiner supports the hip and the sacroiliac joint. Pain in the sacroiliac joint region is suggestive of sacroiliac joint dysfunction.

Lateral compression[16]

The patient lies on theire side. A downward directed compression force is applied with the heel of the hand to the iliac crest on the top. Pain in the sacroiliac joint region is suggestive of sacroiliac joint dysfunction.

Sacral thrust[16]

The patient lies prone on the exam table. A downward directed force is applied with the heel of the examiner's hand centrally over the sacrum. Pain in the sacroiliac joint region is suggestive of sacroiliac joint dysfunction.

The presence of three or more of the provocative tests will increase diagnostic accuracy[17].

Evaluation

Imaging studies help rule out other possible sources of pain. Plain radiographs will identify pathology in the hip and also changes in the sacroiliac joint.

The changes in ankylosing spondylitis are

1. Subchondral bony erosion
2. Subchondral sclerosis and
3. The fusion of the sacroiliac joints

CT scans provide more detailed anatomy of the bony architecture. Radionuclide imaging is not a useful tool for identifying sacroiliac joint dysfunction. MRI scans have a 90% sensitivity in identifying spondyloarthritis but not valuable for non-inflammatory conditions[18].

Image-guided injections are the gold standard to identify sacroiliac joint dysfunction—document both the provocation of symptoms when inflated and relief following local anesthetic infiltration. Image modalities in decreasing order of efficacy are CT guided, Fluoroscopy guided, and ultrasound-guided. When performing injections, direct the needle towards the inferior portion of the joint. Inflate the joint only with 1-2 ml of injectate[19].

Treatment / Management

The initial step in the treatment of sacroiliac joint syndrome is similar to the management of any axial low back pain. This would be an exercise orientated spinal stabilization/stretching program. Belts applied to hold the sacroiliac joints in place have equal benefit as a home exercise program or a structured clinical exercise program in pregnancy-induced sacroiliac joint dysfunction[20]. Analgesics and NSAIDs can help with symptom relief. If there is a triggering mechanism, the patient needs to be counseled on modifying this sport or activity. Therapeutic manipulation, osteopathic manual treatment, and chiropractic adjustments are beneficial[21]. Kinesio taping has also shown positive results[22]. (A1)

Interventional treatments include the following: [19]

1. Prolotherapy – this involves the injection of substances like dextrose and platelet-rich plasma into the joint.
2. Extra-articular or intraarticular steroid injections. Extra-articular or combined is favored to just intra-articular injections.
3. Radiofrequency denervation. Involves lesioning the lateral branch nerves innervating the sacroiliac joint. The area of ablation increases with bipolar and cooled radiofrequency devices. The drawback is that radiofrequency denervation only addresses the posterior nerves. It does not address the anterior nerves.
4. Pulsed radiofrequency. Normal radiofrequency destroys the nerves. Pulsed radiofrequency, on the other hand, creates an electrical field altering the pain transmission in the A-delta and C-fibers.
5. Recalcitrant cases may require surgical intervention. However, results are not uniformly encouraging. Schutz and co-workers [23]showed that 82% of the patients following surgery were unsatisfied, and 65% required re-operation. Recent techniques with triangular implants[24] have had better results, but long term outcomes are awaited.
(A1)

Differential Diagnosis

Ankylosing spondylitis

Insufficiency fracture of the sacrum

Hip fracture

Hip tendonitis

Iliotibial band syndrome

Lumbosacral discogenic pain syndrome

Lumbosacral radiculopathy

Piriformis syndrome

Sacroiliac joint infection

Iliac crest syndrome

Trochanteric bursitis

Prognosis

Correct diagnosis is paramount. History of a precipitating event, repetitive strain, or previous lumbar surgery should be ascertained. Three or more provocative tests should identify the sacroiliac joint as the source of pain. Physical therapy using a stretching/stabilization exercise program is the first line of treatment. Correct any anatomical leg length discrepancy with adjustments to footwear. Pelvic stabilization belts can be useful in pregnancy-induced sacroiliac joint dysfunction. If non-interventional techniques fail to provide benefit, attempt an image-guided injection of a local anesthetic with or without steroid. Injections can be either intraarticular, extra-articular, or combined. The injection should provide pain relief, and provocative tests should become negative following injection. Treat any persistent pain with radiofrequency denervation. The majority of patients can achieve adequate pain relief with these techniques. In recalcitrant cases, minimally invasive trans sacroiliac fusion surgery is an option.

Complications

Injections carry the risk of introducing infection into the joint and inducing bleeding. Ensure strict asepsis and fine epidural needles decrease the chance of bleeding. During image guidance targeting the inferior portion of the joint is essential. Radiofrequency denervation may cause numbness. Wrongly placed electrodes can cause damage to sacral nerves resulting in incontinence, further pain, or limb weakness. Surgery can cause increased pain and neurological damage. Two plane radiography is paramount during percutaneous fusion procedures.