Around the margins of the joint are numerous, discontinuous interwoven bands of dense connec tive tissue; these comprise the first group. These short interosseous sacroiliac ligaments arise on the intermediate and lateral sacral crest and attach to the rough sacropelvic surface of the ilium. Conversely, the second group, the dorsal posterior sacroiliac ligaments, extends from the median and lateral sacral crests, diagonally in a superior direction across the sacral gutter, and attach to the posterior superior spine of the ilium. Particularly prominent is the long dorsal sacroiliac ligament, which is a thickened band extending from the posterior superior iliac spine to the lower transverse tubercle on the lateral sacral crest Fig.
Several structures anchor into these tough ligaments of. A portion of the sacrotuberous ligament attaches laterally to the sacrum where its fibers blend with the long dorsal sacroiliac ligaments of the joint capsule Figs 1. This anchoring portion of the thoracolumbar fascia also forms a prominent raphe separating the multifidus and gluteus maximus muscle see Fig. Remodeling of the joint into the adult, C-shaped orientation with roughened surface occurs after puberty Schunke as cited in Cole et aI The ileal surface develops a crescent-shaped ridge along its long axis see Fig.
These changes in the surface of the joint contribute to its stability and limited range of motion Simonian et al The interlocking surfaces of the joint form the centerpiece in the self-bracing model of. A The superior portion of the 81J 81 , demonstrating its smooth surface and its continuity with the iliolumbar ligament ILL. In both A and 8 , the sacral promontory sp is marked for reference. The orientation figure in the lower right of A indicates superior 8 and lateral L directions. SII function Snijders et al 1 , Vleeming et al 1 c.
The SIJ capsule frequently has defects that allow fluid substances in the joint space to leak out onto surrounding structures. Notably, contrast leaked into the dorsal sacral foramina, where it could be in contact with the dorsal sacral plexus, and into the ventral region in close juxtaposition with the lumbosacral plexus. These represent intriguing pathways whereby the proinflammatory contents of an inflamed joint could leak into the surrounding neural structures of the pelvis Fortin et aI b. A series of age-related degenerative changes occur to the joint, especially after the fifth decade of life.
In this age range, the cartilaginous surfaces of the joints begin to degenerate and ossification. These changes eventually lead to further restricted motion of the joint. Modern imaging has cast doubt on the degree of ankylosis that is reported to occur in the joint after 50 years of age see citations in Cole et al and Chapter Sacrotuberous ligament The sacrotuberous ligament is a specialization derived from the posteroinferior aspect of the SIJ capsule. It is a triangular-shaped structure extend ing between the posterior iliac spines, the SIJ. The female SIJ in Fig.
The boundaries of the joint are marked with arrowheads in A and 8. The anterior boundary is formed by a precise capsule, the posterior boundary being formed by the interweaving of the interosseous ligaments. The joint has a superior limb sl and inferior limb. The orientation arrows in both A and 8 indicate the superior S and anterior A directions. The medial surface is concave and covered with hyaline cartilage with associated fatty deposits; the lateral surface is convex and covered with fibrocartilage. The tendon of the biceps femoris often reaches over the tuberosity to attach to the sacrotuberous ligament Vleeming et al 1 a , and an occasional aberrant extension derived from the biceps femoris establishes the attachment of its entire superior head to this ligament Akita et al The tendons of the deepest laminae of the multifidus often extend under the long dorsal sacroiliac ligament to embed in the sacrotuberous ligament from its superior surface see Fig.
The sacrotuberous ligament can be divided into several large fibrous bands Fig. Its prominent lateral band reaches from the posterior inferior iliac spine to the ischial tuberosity and its medial band connects the coccygeal vertebrae with the ischial tuberosity. The superior band is the thinnest and forms a plate stretching between the.
Several central bands arise from the lateral band and attach to the lower transverse tubercle of the lateral sacral crest.
They share this attachment with the inferior border of the long dorsal SI ligament. Along its medial and superior borders, the sacrotuberous ligament merges with the interosseous ligaments of the SIJ capsule.
The body of the sacrotuberous ligament is made up from the fusion of its multiple bands and is occasionally penetrated by branches from the inferior gluteal neurovascular bundle. The sacrotuberous ligament is positioned to resist nutation of the sacrum and is opposed by the long dorsal SI ligament that is portioned to resist counternutation Vleeming et al a.
Several studies have examined the stability of the pelvis after sectioning the sacrotuberous ligament Borrelli et al 1 , Dujardin et al , Le Blanche. A Posterior view of the sacral region with the multifidus sheath open. Most of the multifidus muscle has been removed, as has the entire gluteus maxim us muscle. The raphe Ra overlaying the inferior end of the multifidus muscle is present.
The posterior surface of the raphe is the attachment of the gluteus maximus muscle. A ridge in the raphe arrowheads indicates its attachment to the long posterior interosseous ligament of the SIJ. The interior border of the raphe blends into the sacrotuberous ligament ST. The piriformis muscle PfM and sciatic nerve SN are seen emerging from the greater sciatic foramen under the raphe.
The deep border of the raphe lies along the long posterior interosseous ligament arrowheads. The posterior superior iliac spine and posterior inferior iliac spine are indicated by black dots.
The consensus of these studies is that the sacrotuberous ligament helps to stabilize the pelvis in the vertical axis. Sacrospinous ligament The sacrospinous ligament is a specialization of the anteroinferior aspect of the SlJ capsule. It is a triangular-shaped structure see Fig. Its distal attachment is to the spine of the ischium. Proximally, its superior fibers blend with those of the SlJ capsule and the sacrotuberous ligament Standing The ligament is thought to be a degenerate portion of the coccygeus muscle Standing Although initially involved in movements of the tail in quadrupeds, this ligament has evolved into a support mechanism for the pelvic floor in humans Abitbol 1 This complicated ligamentous structure plays a key role in the self-bracing mechanism of the pelvis, a mechanism that func tions to maintain the integrity of the low back and pelvis during the transfer of energy from the spine to the lower extremities Vleeming et al a, b.
Tension in the sacrotuberous and long dorsal SI ligaments varies with rocking movements of the sacrum in its joint capsule Vleeming et al a , and unilateral lesions of the SI] capsule increase the range of motion decrease the stability of the joint under compressive loads Simonian et aI 1 The ligamentous support mechanism of the lumbo sacral region is influenced by several major muscle groups in the low back and pelvis; each of these groups will be discussed below.
Major muscle groups associated with the lumbosacral ligamentous structures M ultifidus muscle Fig. All but the deepest laminae of the multifidus muscle Mu have been removed. The sacrotuberous ligaments seen stretching from the ischial tuberosity 1sT to the coccyx cox medially and the posterior iliac spines superolaterally. The posterior superior iliac spine psis and the posterior inferior iliac spine piis are marked on the contralateral side.
The asterisk marks the transverse tuberosity of the lateral sacral crest and the arrowheads mark the course of the long posterior interosseous ligament under the lateral band of the sacrotuberous ligament. The lateral band spans the piriformis muscle PfM to reach the ilium inferior to the piis. As the lateral band climbs toward the psis , it blends with the raphe see Fig. The medial band attaches to the coccyx, and the superior band courses superficial to the long dorsal 81 ligament to connect the coccyx with the posterior ileal spines.
Tendons of the multifidus pass between the superior band and the long dorsal 81 ligament to insert into the body of the sacrotuberous ligament. Summary of the ligamentous structures The ligamentous structures of the lumbosacral connection form a continuous, dense connective. The paravertebral muscles in the lumbar region are represented by three large muscles see Fig. The lateral two muscles, iliocostalis and longissimus, arise from the iliac crest and thoracolumbar fascia, but, with the exception of a few medial slips from the longissimus, do not attach to the lumbar vertebrae.
The multifidus is divided into five bands Fig. Its distal attachments are the sacrum, interosseous SI ligaments, thoracolumbar fascia, and extreme medial edge of the iliac crest. The attachment of the muscles to the thoracolumbar fascia represents a raphe separating the multifidus from the gluteus maximus muscle Figs 1. The anterior border of the raphe is anchored in the SI] capsule, and the posterior border of the raphe becomes part of the thoracolumbar fascia.
Finally, tendinous slips of the multifidus muscle pass under the long dorsal SI ligament to join with the sacrotuberous ligament see Fig.
These connections integrate the multifidus into the ligamentous support system of the SIlo. A Schematic illustrating the three groups of bands forming the sacrotuberous ligament. The lateral band LB overlays the long posterior interosseous ligament arrowheads and reaches upward toward the posterior superior iliac spine. The firmest attachment of the lateral band is to the transverse tubercle TT of the lateral sacral crest. The medial band MB bends toward the coccygeal vertebra. Both of these bands arise on the ischial tuberosity 1sT. A superior band courses upward from the coccygeal attachments to blend with the lateral band over the long posterior interosseous ligament.
B Photograph of the sacrotuberous ligament similar to that depicted in A. The piriformis muscle PfM and sciatic nerve SN are marked for reference.
The fibers of the multifidus are aligned in the vertical plane with only very slight horizontal deviations. However, owing to its geometry, only slight movements in the horizontal plane can be accomplished by this muscle. Finally, by increasing tension on the thoracolumbar fascia, SI ligaments and sacrotuberous ligaments, activation.
Given the importance of this muscle it is easy to understand how its dysfunction could lead to injury of the low back and to low back pain. Alteration in the structure of the multifidus muscle occurs. A The shortest laminae of the multifidus muscle. Each lamina arises from a lumbar spine and attachment is to the sacrum. Adapted from Macintosh et aI 1 In addition, structural changes in the muscle histochemistry, the muscle fiber type, and the myotendinous junction have been reported for the multifidus on the concave side of the lumbar scoliotic curve Khosla et al 1 Lumbar disc herniation is also associated with histochemical changes in the multifidus muscle consistent with atrophy and fibrosis Bajek et al , Lehto et al , Mattila et al , Rantanen et al , Yoshihara et al , , Zhao et al Low back pain has been associated with reduction in size of the multifidus muscle Hides et al , Kader et al , Lee et al , Parkkola et al , Sihvonen et al The thoracolumbar fascia and the tendinous insertion of the iliocostalis Ic and longissimus Lo muscles have been opened to expose the multifidus muscle Mu.
The raphe Ra separating the multifidus and gluteus muscles is seen stretching from the coccyx cox to the posterior superior ilial spine asterisk. Its anterior border is blended with the 81 joint capsule and its posterior border with the thoracolumbar fascia. The rough surface visible on this raphe represents the attachment site for the gluteal muscle.
Reduced size of the muscle and increased fatty deposits typified a population of low back pain patients when compared with a population of healthy volunteers Parkkola et aI Latissimus d orsi muscle The upper extremity is anchored to the body through an anterior muscular hood, the pectoralis muscles, and a posterior muscular hood, the latissimus dorsi.
This latter muscle has its axial attachment to the thoracolumbar fascia Fig. Its appendicular attachment is to the intertubercular.
Agreement seems to be centered around the concept that the muscle is primarily involved in movement of the arm and its influence on movement of the lumbar spine, although slight Bogduk et aI , might provide some stabilizing activity Barker et al , van Wingerden et a1 Gluteus maximus muscle. The superficial fat and fascia have been removed to demonstrate the diamond shape of the thoracolumbar fascia TLF.
Movement, Stability & Lumbopelvic Pain. 2nd Edition. Integration of research and therapy. Authors: Andry Vleeming Vert Mooney Rob Stoeckart. Hardcover. Movement, Stability & Lumbopelvic Pain. Integration of Research and Therapy. Book • 2nd Edition • Edited by: Andry Vleeming, Vert Mooney and Rob.
A small window is present in the fascial sheath on the left, revealing the paravertebral muscles undemeath. Large muscles of the upper extremity trapezius, Tp; latissimus dorsi, Ld and lower extremity gluteus maximus, Gm attach along the borders of the thoracolumbar fascia. The iliac crest and gluteus medius muscle can be seen emerging from under the superolateral border of the gluteus maximus.