When refering to evidence in academic writing, you should always try to reference the primary (original) source. That is usually the journal article where the information was first stated. In most cases Physiopedia articles are a secondary source and so should not be used as references. Physiopedia articles are best used to find the original sources of information (see the references list at the bottom of the article).
If you believe that this Physiopedia article is the primary source for the information you are refering to, you can use the button below to access a related citation statement.
The sacroiliac joint (SIJ) is the largest axial joint in the body. It connects the spine to the pelvis and transfers load between the lumbar spine and the lower extremities.[1] Research has shown the sacrum has very little movement. Numerous ligaments across the joint support and limit movement of the SIJ.[2]
The sacrum tightly wedges between the ilia and the ligaments provide resistance to shear loads.[3] Additional resistance is also provided by grooves and ridges to protect the joint against shearing.[3][4]Although several of the body’s largest and powerful muscles surround the SIJ, no muscle directly affects sacral movements.[2]
Ligaments that play an important role in SIJ stability are the iliolumbar ligament (ventral side), the posterior sacroiliac ligaments, interosseus ligaments, sacrotuberous and sacrospinous ligaments. The pubic ligaments, the anterior sacroiliac ligaments and the dorsal side of the iliolumbar ligaments have the least effect on pelvic stability.[2][3]
Range of Motion
The sacrum can move with respect to the ilium in all directions, but the magnitude of motion is minimal at about 6° of freedom. The SIJ range has three planes of motion: flexion-extension (nutation/counternutation) is approximately 3°, axial rotation is around 1.5° and lateral bending 0.8°.[2]
The two main movements occur when the sacrum moves relative to the iliac bones in the sagittal plane.
Nutation describes when the sacrum is rotated forwards relative to the iliac bones [5][4][6]
Counternutation describes when the sacrum is rotated backwards relative to the iliac bones[5][4][6]which occurs in supine and non-weight-bearing.
According to Willard et al[7] nutation can be regarded as anticipation for joint loading, as it is more stable than counternutation. During nutation, the posterior parts of the iliac bones are compressed into the “keystone-like” shape, and the joint is in the locked and close-packed position[8]. This normally occurs during increased load-bearing situations e.g. standing and sitting, to increase stability[4][9].
Anterior and posterior rotation as the innominate movements occurs in the sagittal plane. Anterior rotation of the innominate should not occur in weight-bearing. To keep the leg stable in single-leg standing, the innominate will posteriorly rotate, to put the sacrum in a nutated position. This will be the close pack position
Inflare and outflare are normal innominate movements around the transverse plane and that occurs during rotation and lateral bending tasks.
The female sacrum is wider, more uneven, less curved and more backwards rotated. The male pelvis tends to be relatively long and narrow, with a longer and more conical pelvic cavity compared to the female pelvis. The female pelvis has a wider sciatic notch and the acetabula are wider apart compared to the male pelvis.[2][14]
These sex differences are also seen in the biomechanics of the SIJ with the female SIJ having higher mobility and greater stresses, greater loads and more pelvis ligament strains compared to the male SIJ. Furthermore, the influence of hormones such as relaxin, which increases the mobility of the SIJ by providing ligament laxity for birth, needs to be considered. All these features may contribute to women being more prone to incidences of SIJ and pelvic pain due to high mobility.[2]
Ligament and muscle-forces are needed to provide compression of the SI joint. This mechanism of compression of the SI joints due to extra forces, to keep an equilibrium, is called ‘force closure.[16]
Superficial and Deep Anatomical Slings
The four muscle slings around the pelvic girdle that contribute to force closure of the pelvis are[17]:
Contraction of these group of muscles provides stability, compressing the pelvic girdle, resulting in force closure of the pubic symphysis
Multidirectional sports such as tennis, soccer, football, basketball rugby and hockey places a great demand on the AOS as it must not only contribute to accelerating the body but also to rotating and decelerating it during the change of direction.
Muscles work as synergists to directly stabilise the pelvic girdle
Force closure increases indirectly due to the anatomical attachments of the gluteus maximus and the thoracolumbar fascia with the sacrotuberous ligament
The sling allows for movement in the sagittal plane while also influencing local stability
Contraction of the sacral part of multifidus causes sacral nutation thereby increasing tension in the interosseus and short dorsal ligaments and thus creating increased force closure of the SIJ[21]
The iliac attachments of multifidus together with erector spinae pull the posterior parts of the iliac bones toward each other and therefore limiting further nutation
Contraction of erector spinae and long head of biceps may increase force closure due to their anatomical attachments with the sacrotuberous ligament.
Contraction of erector spinae and multifidus has broadening effect (inflation of the fascial cylinder), this will increase tension and assist with force closure.
Sling provides stability in the coronal plane and involved in pelvo-femoral stability in dynamic movements (gait, lunges, stair climbing)
To understand the relevance of the lateral sling, the actions of the muscles need to be understood
Hip abduction and medial rotation – gluteus medius and minimus
Tensor Fascia Latae works in synergy with these muscles to hold pelvis level in single leg movements
Tensor Fascia Latae also works with gluteus maximus on ITB to stabilise the hip joint by holding the head of the femur in the acetabulum
Movements involving single-leg stance, such as walking, lateral sling comes into tension to maintain pelvis stable over stance leg and preventing pelvic drop on the opposite side of the pelvis[23]
Failed control of lateral sling often presents a hip drop/ Trendelenburg sign during the stance phase of gait and single-leg stance
A good understanding of the concept of these anatomical slings and the ways in which they function to influence lumbopelvic stability and function will be helpful in deciding on which treatment strategy to apply in patients with pelvic girdle dysfunction.
The integrated model of function has been derived from anatomical and biomechanical studies of the pelvis as well as clinical experience. This model aims to address why the pelvis is painful and not able to sustain and transfer loads as opposed to a model which only seeks to identify specific pain generating structures. The four components of this model are[26]:
Form closure (structure) - the stability of the joint from the design of the pelvic anatomy.
Force closure - forces produced by myofascial action across the joint to create stability[14][8][7]
Motor control (specific timing of muscle action/inaction during loading)
Emotions
This model suggests that multiple factors affect joint mechanics. Some of these factors may be intrinsic to the joint itself, whereas other factors are produced by muscle action. These in turn can be influenced by the emotional state. To effectively manage pelvic girdle pain or dysfunction it is necessary to address all four components to guide patients towards a healthier way to live and move.[26]
Dyspareunia - recurring pain in the genital area or within the pelvis during sexual intercourse
Genital pain
Anal pain
Condition is often misdiagnosed and mistreated[34]
Causes may be excessive sitting or cycling
Lymph Nodes in the Abdominal/Pelvis Area
Lymphatic System
The majority of lymph nodes are in the abdominal area. When treating a patient with pelvic girdle dysfunction it is important to consider the vascular system and the lymphatics' role in inflammation. [10]
↑ 3.03.13.2Zlomislic V, Garfin SR. Anatomy and Biomechanics of the Sacroiliac Joint. Techniques in Orthopaedics. 2019 Jun 1;34(2):70-5.
↑ 4.04.14.24.34.4Le Huec JC, Bourret S, Thompson W, Daulouede C, Cloché T. A painful unknown: sacroiliac joint diagnosis and treatment. EFORT Open Reviews. 2020 Oct;5(10):691-8.
↑ 5.05.1Toyohara R, Kurosawa D, Hammer N, Werner M, Honda K, Sekiguchi Y, Izumi SI, Murakami E, Ozawa H, Ohashi T. Finite element analysis of load transition on sacroiliac joint during bipedal walking. Scientific reports. 2020 Aug 13;10(1):1-0.
↑ 7.07.1Willard F.H, Vleeming A, Schuenke M.D, Danneels L & Schleip R. The thoracolumbar fascia: anatomy, function and clinical considerations. Journal of Anatomy 2012; 221(6): 507-36
↑ 8.08.1Pool-Goudzwaard A.L, Vleeming A, Stoeckart R, Snijders C. J & Mens J.M.A. Insufficient lumbopelvic stability: a clinical, anatomical and biomechanical approach to ‘a-specific’ low back pain. Manual Therapy. 1998; 3(1): 12-20
↑Vleeming A, Stoeckart R, Volkers, ACW, Snijders CJ. Relation between form and function in the sacroiliac joint. Part 1: Clinical anatomical aspects. Spine 1990a; 15(2): 130-132
↑ 10.010.110.210.3Riczo, D. Biomechanics and Dynamics of the Pelvic Girdle. Plus Course. 2021
↑ 13.013.1Cho HJ, Kwak DS. Movement of the sacroiliac joint: Anatomy, systematic review, and biomechanical considerations. Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine. 2020 Nov 30:0954411920978021.
↑ 14.014.1Vleeming A, Schuenke MD, Masi AT, Carreiro JE, Danneels L, Willard FH. The sacroiliac joint: an overview of its anatomy, function and potential clinical implications. Journal of anatomy. 2012 Dec;221(6):537-67.
↑ 17.017.117.217.3Lee, D; Vleeming, A; Jones, M. The Pelvic Girdle: An Integration of Clinical Expertise and Research. Edinburgh: Elsevier/Churchill Livingstone, 2011.
↑Lee JK, Lee JH, Kim KS, Lee JH. Effect of abdominal drawing-in maneuver with prone hip extension on muscle activation of posterior oblique sling in normal adults. Journal of Physical Therapy Science. 2020;32(6):401-4.
↑Yoga Anatomy. Posterior Oblique sling system - Myofascial slings - (Vleeming & Lee). Available from https://www.youtube.com/watch?v=YpJbL-IA-wA. (last accessed 20 December 2020)
↑Vleeming, A; Mooney, V; Stoeckart, R. Movement, Stability & Lumbopelvic Pain, Integration of Research and Therapy. UK: Churchill Livingstone, 2007
↑Physiopedia. Slings & Sacroiliac Joint Pain by Ismail Saracoglu, University of Nottingham. Available from https://www.youtube.com/watch?v=pBgZoApSltY. (last accessed 20 December 2020)
↑ 26.026.1Lee D, Hodges P. Principles of the integrated model of function and its application to the lumbopelvic-hip region. The Pelvic Girdle, ed. 2004;3:41-54.
