Chapter 27

1. Chapter 27 The Sacroiliac Joint

2. Overview • The sacroiliac joint (SIJ), which serves as the point of intersection between the spinal and the lower extremity joints is the least understood and, therefore, one of the most controversial and interesting areas of the spine

3. Anatomy • The ilium, ischium, and pubic bone fuse at the acetabulum to form each innominate • Each of the two innominates articulate with the sacrum, forming the sacroiliac joint, and with each other at the symphysis pubis

4. Anatomy • The sacrum is a strong and triangular bone located between the two innominates • Provides stability to this area and transmits the weight of the body from the mobile vertebral column to the pelvic region

5. Anatomy • The articulating surfaces of the sacroiliac joint differ • The iliac joint surfaces are formed from fibrocartilage • The sacral surfaces are formed from hyaline cartilage. • The hyaline cartilage is 3-5 times thicker than the fibrocartilage, so that between the sacral and iliac auricular surfaces, the sacroiliac joint is deemed a synovial articulation, or diarthrosis

6. Anatomy • The configuration of the sacroiliac joints is extremely variable from person to person, and between genders in terms of morphology and mobility • These differences are not pathological, but are normal adaptations

7. Anatomy • Like other synovial joints, the sacroiliac joint is reinforced by ligaments, but the ligaments of the sacroiliac joint are some of the strongest and toughest ligaments of the body

8. Anatomy • The anterior sacral ligament (ASL) is an anterior-inferior thickening of the fibrous capsule • Relatively weak and thin compared to the rest of the sacroiliac ligaments • Extends between the anterior and inferior borders of the iliac auricular surface, and the anterior border of the sacral auricular surface

9. Anatomy • The interosseous ligament is a short ligament located deep to the dorsal sacroiliac ligament • Forms the major connection between the sacrum and the innominate, filling the irregular space posterior-superior to the joint between the lateral sacral crest, and the iliac tuberosity

10. Anatomy • The dorsal sacroiliac ligament (long ligament) connects the PSIS (and a small part of the iliac crest) with the lateral crest of the third and fourth segment of the sacrum • This is a very tough and strong ligament • Sacral nutation (anterior motion) of the sacrum appears to slacken this ligament whereas counternutation (posterior motion) tautens the ligament

11. Anatomy • The sacrotuberous ligament is comprised of three large fibrous bands, broadly attached by its base to the posterior inferior iliac spine, the lateral sacrum, and partly blended with the dorsal sacroiliac ligament • Stabilizes against nutation (forward rotation) of the sacrum • Counteracts against the dorsal and cranial migration of the sacral apex during weight bearing

12. Anatomy • The sacrotuberous ligament extends from the ischial spine to the lateral margins of the sacrum and coccyx, and laterally to the spine of the ischium • Counteracts against nutation of the sacrum

13. Anatomy • The pubic symphysis is classified as a symphysis as it has no synovial tissue or fluid, and contains a fibrocartilaginous disc • The bone surfaces of this joint are covered with hyaline cartilage, but are kept apart by the presence of the disc

14. Anatomy • Thirty-five muscles attach directly to the sacrum and/or innominate • These muscles primarily function to stabilize the sacroiliac joint rather than to move it

15. Anatomy • The piriformis muscle • Primarily functions to produces external rotation and abduction of the femur • Also thought to function as an internal rotator and abductor of the hip if the hip joint is flexed beyond 90° • Capable of restricting sacroiliac joint motion

16. Anatomy • The term “pelvic floor muscles” primarily refers to the levator ani, a muscle group composed of the pubococcygeus, puborectalis and iliococcygeus • The levator ani muscles join the coccygeus muscles to complete the pelvic floor • The pelvic floor muscles work in a coordinated manner to increase intra-abdominal pressure, provide rectal support during defecation, inhibit bladder activity, help to support the pelvic organs, and assist in lumbopelvic stability

17. Anatomy • Neurology • It remains unclear precisely how the anterior and posterior aspects of the sacroiliac joint are innervated, although the anterior portion of the joint likely receives innervation from the posterior rami of the L2‑S2 roots • Contribution from these root levels is highly variable and may differ among the joints of given individuals • It is the joint’s highly variable and complex innervation that produces a very diffuse pattern of pain referral from this area

18. Biomechanics • The pelvic area must function to absorb the majority of the lower extremity rotation, while still permitting motion to occur • It is likely, that the movement of the pelvis is in the nature of deformations and slight gliding motions around a number of undefined axes, with the joints of the pelvic ring deforming in response to body weight and ground reaction forces

19. Biomechanics • There is very little agreement, either among disciplines, or even within disciplines about the biomechanics of the pelvic complex. The results from the numerous studies on mobility of the sacroiliac joint have led to a variety of different hypotheses and models of pelvic mechanics over the years

20. Biomechanics • Osteopathic model • The sacrum rotates around two oblique axes • The innominates are capable of rotating anteriorly and posteriorly • Distinction made between sacroiliac impairment and iliosacral impairment

21. Biomechanics • Chiropractic model • As one innominate flexes, the ipsilateral sacral base moves anterior and inferior, and as the other innominate extends, the sacral base on that side moves posterior and superior

22. Biomechanics • Biomechanical model • When the sacrum nutates, or flexes, relative to the innominate, a linear glide occurs between the two L-shaped articular surfaces of the sacroiliac joint. • The shorter of the two lengths, level with S 1, lies in a vertical plane • The longer length, spanning S 2-4, lies in an anterior-posterior plane

23. Biomechanics • Snijders and Vleeming defined kinetics within the lumbar/pelvic/hip region by introducing the concepts of ‘extrinsic’ and ‘intrinsic’ stability of the pelvic girdle and the ‘self-locking’ mechanism • Their work instituted the terms form closure and force closure to describe the passive and active forces that help to stabilize the pelvis and the sacroiliac joint

24. Biomechanics • Form closure • Form closure refers to a state of stability within the pelvic mechanism, with the degree of stability dependent upon its anatomy, with no need for extra forces to maintain the stable state of the system • Relies on incongruity of the articular surfaces, the friction coefficient of the articular cartilage and the shape of the articulating surfaces

25. Biomechanics • Force closure • Force closure requires intrinsic and extrinsic forces to keep the sacroiliac joint stable • These dynamic forces involve the neurological and myofascial systems, and gravity. Together, these components produce a self-locking mechanism for the sacroiliac joint • Critical to the self-locking mechanism is the ability of the sacrum to nutate

26. Examination • Under the premise that a relationship between pelvic asymmetry and low back pain exists, orthopedic, osteopathic, and physical therapy texts promote the use of pain provocation (symptom-based) tests and biomechanical (mechanical-based) tests that include static (positional) and dynamic (motion or functional) tests

27. Examination • Given the questionable reliability and validity of the tests for the sacroiliac joint, the clinician should guard against forming a diagnosis based on the results of a few tests • Ideally, the diagnosis needs to be based on the results from a thorough biomechanical examination that includes pain provocation and static and dynamic tests

28. Examination • As several recent studies have found improved inter-rater reliability in the diagnosis of low back pain when using a combination of physical examination procedures as opposed to a single model approach, it might be logical to assume that a similar approach would work with the SIJ

29. Examination • History that indicates SIJ dysfunction • A history of sharp pain awakening the patient from sleep upon turning in bed • Pain with walking, ascending or descending stairs, standing from a sitting position, or with hopping or standing on the involved leg • A positive straight leg raise at, or near, the end of range (occasionally early in the range when hyperacute), pain, and sometimes limitation, on extension and ipsilateral side bending of the trunk

30. Examination • Systems Review • Given the number of visceral organs in the vicinity of the sacroiliac joint, a thorough systems review is needed to rule out a visceral source for the symptoms

31. Examination • Observation • An examination of posture is performed to check for the presence of asymmetry • However, as pelvic landmark asymmetry is probably the norm, ‘positive findings’ are to be expected

32. Examination • Hip Range of Motion • The evidence to demonstrate whether hip rotation is limited in patients with signs of sacroiliac joint dysfunction is inconclusive

33. Examination • Palpation of bony landmarks • An altered positional relationship within the pelvic girdle should only be considered positive if a mobility restriction of the sacroiliac joint and/or pubic symphysis is also found

34. Examination • Weight bearing and non-weight bearing kinetic tests • These tests are designed to assess the osteokinematics occurring at the sacroiliac joint during patient generated movements • The tests assess the mobility of the innominate, and the ability of the sacrum to nutate (ipsilateral test), and to side bend (contralateral test)

35. Examination • The short and long-arm tests • These tests are used to confirm or refute the findings from the kinetic tests

36. Examination • Sacroiliac Joint Stress Tests • Designed to assess the integrity of the joint and the surrounding ligaments • Believed to be sensitive for severe arthritis or ventral ligament tears, although they have been shown to be poorly reproducible

37. Intervention • Thus far, the success of interventions at this joint has been mixed, due in part to the poor reliability with many of the examinations used • The success of any intervention depends on the quality and accuracy of the examination and the subsequent evaluation

38. Intervention • It follows that if the examination gives an inaccurate diagnosis, the intervention may have a mixed result • Given that the chosen intervention for the sacroiliac joint, like the spine, depends largely on the philosophy or background the clinician uses to establish the diagnosis, a variety of diagnoses for the same biomechanical dysfunction can arise

39. Intervention • Acute phase goals: • Decrease pain, inflammation, and muscle spasm • Increase weight bearing tolerance, where appropriate • Promote healing of tissues through sufficient stabilization (may require belt) • Increase pain-free range of sacroiliac joint motion • Regain soft tissue extensibility around the pelvic region • Regain neuromuscular control • Allow progression to the functional stage

40. Intervention • Functional phase goals: • To significantly reduce or to completely resolve the patient’s pain • To restore full and pain-free sacroiliac joint range of motion • To integrate the lower kinetic chains into the rehabilitation • Complete restoration of gait, where appropriate • The restoration of pelvic and lower quadrant strength and neuromuscular control