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Tuesday, June 6, 2023

Stabilization of the Sacroiliac Joint via Muscular Contraction in Vivo

Brent Brookbush

Brent Brookbush


Research Review: Stabilization of the Sacroiliac Joint in Vivo: Verification of Muscular Contribution to Force Closure of the Pelvis.

By Erik Korzen DC, NASM-CES, Acupuncturist

Edited by Brent Brookbush DPT, PT, COMT, MS, PES, CES, CSCS, ACSM H/FS

Original Citation: Vleeming, A., van Wingerden, J.P., Buyruk, H.M., Raissadat, K. Stabilization of the sacroiliac joint in vivo: verification of muscular contribution to force closure of the pelvis. European Spine Journal, 2004. 13: 199-205. Full Article.

Why is this relevant?: The sacroiliac joint (SIJ) is a complex structure with osseous, articular, ligamentous and muscular structures aiding in stabilization. Additionally, the SIJ may be seen as a bridge between the extremities and the lumbo-pelvic hip complex, especially the relationship between the hip and lumbar spine. This study provides in-vivo (in living subjects) findings regarding the contribution of specific muscles to force closure of the SIJ. (Force closure refers to increased rigidity of the SIJ via compression forces imparted by tissues crossing the joint). The researchers utilized Color Doppler Imaging (CDI) and electromyographic (EMG) findings during oscillations to the pelvis to determine muscle activity (refer to the image below for positioning of the apparatus). The results of this study imply that muscle activation increases stiffness (stabilization), and may play a role in preventing shear and stiffness.

Outline of test position for combined color Doppler imaging (CDI) and electromyographic (EMG) measurements. A: Location of the CDI probe over both sacrum and ilium on one side of the pelvis. B: Positioning of the oscillator plate against the anterior superior iliac spine

Study Summary

Study DesignExperimental Study
Level of EvidenceLevel of Evidence IIB: Evidence from at least one other type of quasi-experimental study
Subject Demographics6 Female Subjects:
  • Average age 22 years, standard deviation (SD) of 2.6 years
  • Initial group was comprised of 15 female subjects
  • Only 6 subjects demonstrated adequate mobility, determined by color doppler imaging (CDI) during oscillations
Outcome Measures

Hypothesis: Contraction of selected muscles increases SIJ stiffness


  • Subjects positioned prone
  • Anterior inferior iliac spine (ASIS) is in contact with oscillator plate, vibrations occurred at frequency of 200 Hz
  • Maximum voluntary contraction (MVC) determined for each muscle prior to testing
  • Sacroiliac joint (SIJ) stiffness determined without any muscular contraction via CDI (color Doppler imaging)
  • Threshold difference (THD) is the difference between the vibratory (oscillatory) stimulus on the ASIS and the vibrations measured on the sacrum.  A large difference between the two implies less stiffness.
  • Surface electromyographic (EMG) was placed on the following muscles:

  • Sustained muscle contractions of 10 seconds were performed in a randomized order, 3 times for each subject (Mean EMG levels for each of the 4 muscles was calculated during the 3 repetitions)
  • THD reduced significantly during all muscle activation, but most notably during erector spinae, gluteus maximus and biceps femoris activation - mean results demonstrate significant increase in SIJ stiffness during all muscle contractions.

Activation of the selected muscles resulted in increased stiffness of the SIJ.  The erector spinae, gluteus maximus and biceps femoris muscles were shown to have the greatest effect on SIJ stiffness; the latissimus dorsi had less of an impact.

Although the target muscle had the highest level of EMG activity during all tests, co-contraction did occur. This co-contraction was most apparent during the gluteus maximus test; during which increased activity of the biceps femoris and erector spinae was noted.  Increased activity of the erector spinae was also noted during the biceps femoris and latissimus dorsi tests.

Conclusions of the Researchers

Based on previous studies that involve in vitro anatomic relationships, it is obvious that biceps femoris and gluteus maximus muscles can increase force closure through the SIJ via their attachments on the sacrotuberous ligament. Another key anatomic relationship exits between the gluteus maximus, latissimus dorsi and the thoracolumbar fascia, whereby these 2 muscles can create force closure through the SIJ.

The findings of this study contribute to an already established base of research regarding co-activation of posterior muscles. Results from this study show that SIJ stiffness is influenced directly by specific muscle activity and more importantly, by global motor patterns.

The present study supports the notion that load transfer from the lower extremities to the spine is enhanced by muscle actively compressing the SIJ; increasing stiffness and decreasing glide/shear.

Illustration of the Posterior Oblique Subsystem with Muscles Labeled
Caption: Illustration of the Posterior Oblique Subsystem with Muscles Labeled

Posterior Oblique Subsystem, depicted above are the Sacroiliac joint, Latissimus dorsi, Erector Spinae, Gluteus Maximus, Biceps Femoris and Sacrotuberous ligament


The current study contributes to previously conducted research on sacroiliac joint (SIJ) stability and posterior muscle activation. In the present study, an oscillation plate was used to impart a force through the pelvis and across the SIJ. The oscillations across the SIJ were than recorded on the sacrum using color doppler imaging (CDI). Increased stiffness was defined as an increase in oscillations recorded on the sacrum. This study demonstrates that activating certain muscles increases SIJ stiffness and may enhance load transfer. The researchers note that the findings of this study may have implications for all joints relative to joint stiffness, force transfer and muscular contraction - further research is recommended.

Strengths of this study include, a rather novel use of oscillations to measure joint stiffness in living individuals, helping to advance research that has previously been limited to cadaver study. Although the prone position of the patients and use of manual muscle tests is unlikely to resemble the muscle activation of activities of daily living or functional tasks, this study takes a large step toward understanding the integrated relationship of anatomical structures of the SIJ and their function in living subjects. Further, the use of prior cadaver research contributed to the selection of relevant muscles for this study, resulting in rather poignant findings.

It is worth noting that only 6 of 15 healthy female subjects demonstrated enough SIJ mobility to take part in the study. This could imply that the findings of this study do not occur in all individuals, or at the very least that more sensitive testing methods should be developed. Last, this study was done on healthy, asymptomatic subjects only; care should be taken when considering the implications of this study in a clinical setting.

Why is this study important?

The use of a novel approach for measuring joint stiffness advanced research on the function of muscles crossing the sacroiliac joint. Prior to this study, research regarding the function of these muscles and the SIJ had been limited to hypothesis based on cadaver study. This study demonstrates that activation of the gluteus maximus , biceps femoris , erector spinae, and to a lesser extent the latissimus dorsi increases SIJ stiffness.

How does it affect practice?

Although a fairly convoluted topic among human movement professionals, motion and dysfunction of the sacroiliac joint has be hypothesized as a source of pain and a link between core and lower extremity function/impairment. This study indicates that hyper-, and/or hypo-mobility of the SIJ may be related to the relative activity and function of the gluteus maximus , biceps femoris , erector spinae, and to a lesser extent the latissimus dorsi . For those human movement professionals assessing and addressing SIJ function, it would seem prudent to include specific assessment and interventions for these muscles. Further, these muscles are included in the posterior oblique subsystem (POS) and deep longitudinal subsystems (DLS) which may deserve further study.

How does it relate to Brookbush Institute Content?

Because of the extensive nature of posterior muscle groups, T/L fascia and the SIJ, the predictive models of lumbopelvic-hip complex dysfunction (LPHCD) , lumbosacral dysfunction (SIJD) , upper body dysfunction (UBD) and lower body dysfunction (LLD) may be affected by or potentially the cause of impairment in the function of this joint. Comprehensive analysis of the SIJ would include dynamic posture/movement assessment (Overhead Squat Assessment) , as well as assessment of the hip , sacroiliac joint, lumbar and thoracic spine. A conceptual framework for integrating the findings of this study into practice may be found in the Brookbush Institute's discussion on core subsystems, specifically the posterior oblique subsystem (POS) and intrinsic stabilization subsystem (ISS) .

The videos below address the SIJ and other associated structures as part of assessment, activation and integration techniques.

Overhead Squat Assessment Sign Cluster: Asymmetrical Weight Shift

Open Books (Spine and SIJ mobilization):

Glute Activation:

Static Lunge to Unilateral Row:


  1. Vleeming, A., van Wingerden, J.P., Buyruk, H.M., Raissadat, K. Stabilization of the sacroiliac joint in vivo: verification of muscular contribution to force closure of the pelvis. European Spine Journal, 2004. 13: 199-205.

© 2016 Brent Brookbush

Questions, comments, and criticisms are welcomed and encouraged -