eMedicine Specialties > Sports Medicine > Spine

Sacroiliac Joint Injury

Author: Andrew L Sherman, MD, MS, Associate Professor of Clinical Rehabilitation Medicine, Vice Chairman, Chief of Spine and Musculoskeletal Services, Program Director, SCI Fellowship and PMR Residency Programs, Department of Rehabilitation Medicine, Leonard A Miller School of Medicine, University of Miami
Coauthor(s): Robert Gotlin, DO, Assistant Professor, Department of Physical Medicine and Rehabilitation, Albert Einstein College of Medicine; Director of Orthopaedic and Sports Rehabilitation, Department of Orthopedic Surgery, The Continuum Center for Health and Healing, Beth Israel Medical Center
Contributor Information and Disclosures

Updated: Apr 28, 2008

Introduction

Background

Lower back pain is one of the most prevalent sports maladies, affecting athletes in nearly every sport. Diagnosing the cause of a back injury is quite difficult and challenging because multiple structures in the lower back region can cause pain. However, an accurate diagnosis is paramount to providing successful treatment of the spine injury.

Although still somewhat controversial, the sacroiliac joint (SIJ) is generally accepted as an anatomic structure within the lumbar complex that if injured can be a cause of lower back pain. Mechanical dysfunction, inflammation, infection, trauma, and degeneration all have been attributed to the SIJ. Once the diagnosis of SIJ injury is established, specifically directed treatment can lead to satisfying results. This article discusses the diagnosis, management, and rehabilitation of sacroiliac injuries and pain.

For excellent patient education resources, visit eMedicine's Osteoporosis and Bone Health Center and Back, Neck, and Head Injury Center. Also, see eMedicine's patient education articles Back Pain and Lumbar Disc Disease.

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Lumbar Disk Problems in the Athlete
Lumbosacral Spine Sprain/Strain Injuries
Mechanical Low Back Pain

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Frequency

United States

The incidence of lower back pain in humans parallels the incidence of the common cold, with a lifetime rate approaching 95%. Goldwaith and Osgood first discussed the possibility that SIJ injury could cause low back pain as early as 1905.¹ In the decades since then, several attempts have been made to establish the prevalence of SIJ syndrome in persons with back pain, and the results of these reports vary widely.

Schwarzer et al remarked that "the prevalence of sacroiliac pain would appear to be at least 13% and perhaps as high a 30%" in patients with low back and buttock pain.² Bernard and Kirkaldy-Willis reported the prevalence rate to be 22.5% in 1293 patients with back pain.³

Functional Anatomy

The SIJ is a true diarthrodial joint that joins the sacrum to the pelvis.^4,5,6 In this joint, hyaline cartilage on the sacral side moves against fibrocartilage on the iliac side. The joint is generally C shaped with 2 lever arms that interlock at the second sacral level. The joint contains numerous ridges and depressions, indicating its function for stability more than motion. However, studies have documented that motion does occur at the joint; therefore, slightly subluxed and even locked positions can occur.^2,7

Stability is provided by the ridges present in the joint and by the presence of generously sized ligaments. The ligamentous structures offer resistance to shear and loading. The deep anterior, posterior, and interosseous ligaments resist the load of the sacrum relative to the ilium. More superficial ligaments (eg, sacrotuberous ligament) react to dynamic motions (eg, straight-leg raising during physical motion). The long dorsal sacroiliac ligament can become stretched in periods of reduced lumbar lordosis (eg, pregnancy).

Many large and small muscles have relationships with these ligaments and the SIJ, including the piriformis, biceps femoris, gluteus maximus and minimus, erector spinae, latissimus dorsi, thoracolumbar fascia, and iliacus. Any of these muscles can be involved with a painful SIJ. As a true joint, the SIJ is a pain-sensitive structure richly innervated by a combination of unmyelinated free nerve endings and the posterior primary rami of L2-S3. The wide possibility of innervation may explain why pain emanation from the joint can manifest in so many various ways, with different and unique referral patterns for individual patients.

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Sport-Specific Biomechanics

The function of the SIJ is to dissipate loads of the torso through the pelvis to the lower extremities and vice versa. The pelvis acts as a central base through which large forces are accepted and dissipated. Although the main role of the joint is to provide stability, the SIJ has limited motion that allows it to dissipate and transfer significant loads and stresses. Studies by Weisel indicate that most movement occurs when rising from the sitting to the standing position. However, the amount of motion is small, making assessment of sacroiliac motion during physical examination quite difficult. Selvik suggested that hyperextension produces the greatest degree of motion (2° on average, with only minimal translation of 0.5-1.6 mm).

If the motion in the pelvis is asymmetric, then dysfunction can occur. Some conditions that cause asymmetric motion include leg-length inequalities, a unilaterally weak lower limb (eg, polio), tight myofascial structures (eg, iliopsoas), and scoliosis. Hip osteoarthritis can lead to leg-length shortening and SIJ pain.

Women may be at increased risk for SIJ problems because their broader pelvises, greater femoral neck anteversion, and shorter limb lengths lead to different, possibly predisposing, biomechanics. In addition, pregnancy often leads to stretching of the pelvis, specifically targeting the sacroiliac ligaments and possibly leading to dysfunction, hypermobility syndromes, and chronic pain.

Innervation

The nerve supply of the SIJ originates from multiple lumbosacral root levels with partial innervation from L2 (anterior joint) to S3 (posterior joint). Because the root innervation can vary so widely, the pain referral patterns from primary sacroiliac pain can also vary. Fortin et al interviewed multiple patients documented to have sacroiliac pain by anesthetizing the joint with lidocaine injections under fluoroscopic guidance.^8,9 He found referral patterns ranging from localized buttocks pain to frank radicular leg pain and many other descriptions in between.

Clinical

History

The key element in the diagnosis of sacroiliac dysfunction is pain. Many authors have attempted to define a typical pain pattern associated with the SIJ. Several of these reports describe patients reporting pain in one or both buttocks at or near the posterior superior iliac spine (PSIS). However, pain radiating to the hip, posterior thigh, or even calf has been described.

Patients often relate that pain especially worsens when they have been sitting for long periods or when they perform twisting or rotary motions.

• Pain quality: The pain is described as a dull ache or sharp, stabbing, or knifelike.
• Pain distribution: Reported distributions are the buttocks, back of the thigh, and upper back; it can be unilateral or bilateral.
• History: Importantly, exclude a history of inflammatory disorders (eg, inflammatory bowel disease, Reiter syndrome).
• Fevers, weight loss, and pain in the night with night sweats: These are potential red flags for a systemic illness.
• Pain that is worse in the morning (morning stiffness) and resolves with exercise: This pattern is consistent with an inflammatory disease.

Physical

The reliability of the physical examination findings to diagnose SIJ dysfunction has been addressed in several articles. The usual pattern of examination is discussed, as follows:

• Inspection often reveals a pelvis with asymmetric height. This finding can be an indication of unilateral restriction in motion of one or both SIJs. Standing flexion testing involves the comparison of the symmetry of motion between the PSIS on the tested side and the S2 spinous process (Gillet test). However, Freburger and Riddle questioned the reliability of examinations between testers.¹⁰
• Of paramount importance is to measure the limb lengths to look for inequality, inspect the lumbar spine to look for scoliosis, and rotate the hips to look for motion restriction.
• Palpation may be the most reliable indication of SIJ pain. The patient usually places a thumb directly onto one particular spot in the dimple of the PSIS (sacral sulcus). The patient can usually precisely reproduce the pain over that one spot (Fortin finger sign).⁹ More diffuse back or buttock and leg pain should prompt the clinician to question the diagnosis of SIJ dysfunction (see Differentials and Other Problems to Be Considered).
• Upon neurologic examination, motor strength, sensory examination, and reflexes in the lower extremities should all prove normal. However, sometimes, strength examination proves challenging, and the patient may exhibit weaknesses because of pain inhibition or frank muscle imbalance that developed during episodes of pain and relative inactivity. True neurogenic weakness, numbness, or loss of reflex should alert the clinician to consider nerve root injury or pathology other than a mechanical dysfunction.
• Perform pain provocation tests.^{9,11,12,13,14}  Distraction can be performed to the anterior sacroiliac ligaments by applying pressure to the anterior superior iliac spine (iliac gapping test). Apply compression to the joint with the patient lying on his or her side. Pressure is applied downward to the uppermost iliac crest (iliac compression test). The goal of the Gaenslen test is to apply torsion to the joint. With one hip flexed onto the abdomen, the other leg is allowed to dangle off the edge of the table. Pressure should then be directed downward on the leg in order to achieve hip extension and stress the SIJ.For the flexion, abduction, and external rotation (FABER or Patrick) test, the examiner externally rotates the hip while the patient lies supine. Then, downward pressure is applied to the knee.In all tests, pain in the typical area raises suspicion for an SIJ lesion.
• Unfortunately, although systematic, these tests have not proven reliable in controlled studies. Dreyfuss and colleagues studied 12 SIJ tests in relation to fluoroscopically guided SIJ injection.¹⁵ They were unable to find even one of these tests to be highly sensitive or specific for diagnosing SIJ pain. Hancock et al also published a review on physical examination testing reliability to diagnose SIH syndrome.¹² Stuber conducted a systematic review of the literature to determine the specificity, sensitivity, and predictive values of such clinical tests of the sacroiliac joint.¹¹ According to the author, "the search was conducted using several online databases: Medline, Embase, Cinahl, AMED, and the Index to Chiropractic Literature. Reference and journal searching and contact with several experts in the area was also employed." Stuber concluded that the distraction test, compression test, thigh thrust/posterior shear, sacral thrust, and resisted hip abduction were the only tests to have specificity and sensitivity greater than 60% in at least one study, and that further investigation is warranted to determine which tests or combinations of these tests are the best for diagnosing SIJ dysfunction. 

Causes

Many patients state that their pain began spontaneously, whereas others can cite a specific inciting event. Bernard and Kirkaldy-Willis reported that 58% of patients diagnosed with SIJ pain based on clinical examination findings had some inciting traumatic injury.³

Many risk factors are associated with lower back pain, and many are directly associated with lumbar disk injury. These include, but are not limited to, smoking, poor physical condition, positive family history, and occupational lifting.

Factors that specifically increase the likelihood of mechanical injury to the SIJ have not been identified. Pregnancy is one particular condition attributed to SIJ dysfunction.

In the authors’ experience, certain biomechanical or muscle length imbalances may ultimately predispose a person to sacroiliac dysfunction and pain. Likely, this is a result of altered gait patterns and repetitive stress to the SIJ and related structures. These conditions exist in persons with leg-length inequality, scoliosis, a history of polio, poor-quality footwear, and hip osteoarthritis.

Related eMedicine topics:
Lumbar Degenerative Disk Disease
Lumbar Disk Problems in the Athlete
Lumbosacral Spine Sprain/Strain Injuries
Mechanical Low Back Pain

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