Quantifying lumbar paraspinal intramuscular fat: Accuracy and reliability of automated thresholding models.

Background: The reported level of lumbar paraspinal intramuscular fat (IMF) in people with low back pain (LBP) varies considerably across studies using conventional T1- and T2-weighted magnetic resonance imaging (MRI) sequences. This may be due to the different thresholding models employed to quantify IMF. In this study we investigated the accuracy and reliability of established (two-component) and novel (three-component) thresholding models to measure lumbar paraspinal IMF from T2-weighted MRI. Methods: In this cross-sectional study, we included MRI scans from 30 people with LBP (50% female; mean (SD) age: 46.3 (15.0) years). Gaussian mixture modelling (GMM) and K-means clustering were used to quantify IMF bilaterally from the lumbar multifidus, erector spinae, and psoas major using two and three-component thresholding approaches (GMM2C; K-means2C; GMM3C; and K-means3C). Dixon fat-water MRI was used as the reference for IMF. Accuracy was measured using Bland-Altman analyses, and reliability was measured using ICC3,1. The mean absolute error between thresholding models was compared using repeated-measures ANOVA and post-hoc paired sample t-tests (α = 0.05). Results: We found poor reliability for K-means2C (ICC3,1 ≤ 0.38), moderate to good reliability for K-means3C (ICC3,1 ≥ 0.68), moderate reliability for GMM2C (ICC3,1 ≥ 0.63) and good reliability for GMM3C (ICC3,1 ≥ 0.77). The GMM (p < .001) and three-component models (p < .001) had smaller mean absolute errors than K-means and two-component models, respectively. None of the investigated models adequately quantified IMF for psoas major (ICC3,1 ≤ 0.01). Conclusions: The performance of automated thresholding models is strongly dependent on the choice of algorithms, number of components, and muscle assessed. Compared to Dixon MRI, the GMM performed better than K-means and three-component performed better than two-component models for quantifying lumbar multifidus and erector spinae IMF. None of the investigated models accurately quantified IMF for psoas major. Future research is needed to investigate the performance of thresholding models in a more heterogeneous clinical dataset and across different sites and vendors.

Is fatty infiltration in paraspinal muscles reversible with exercise in people with low back pain? A systematic review.

PURPOSE: Increased fatty infiltration in paraspinal muscles has been recognized as a feature of muscle quality loss in people with Low Back Pain (LBP) and is highly associated with the severity of LBP and dysfunction. Reducing fatty infiltration has been recognized as a rehabilitation aim. An earlier systematic review published in 2014 revealed conflicting evidence for the reversibility of paraspinal muscle quality by means of exercise and no updates have been published since. A new systematic literature search is warranted. METHOD: Pubmed, CINAHL and Embase were searched from inception to July 2022. Randomized, non-randomized controlled trials (RCT and non-RCT) and single-arm trials were included if they reported the effect of exercise on paraspinal fatty infiltration in people with LBP. Effect sizes and statistical power were calculated for (1) exercise versus control, and (2) pre-post exercise changes. Available data from the RCTs were pooled via meta-analysis when appropriate. Otherwise, data were synthesized qualitatively. RESULTS: Two RCTs, one non-RCT and three single-arm trials met the selection criteria. Data were not pooled due to substantial clinical heterogeneity. Effect sizes from the RCTs revealed no significant difference for exercise versus control. One single-arm trial with high risk of bias demonstrated a significant pre-post difference with moderate effect size, but only at one (T12-L1) of the investigated levels. CONCLUSION: Moderate quality evidence is available that paraspinal fatty infiltration is not reversible with exercise in people with LBP. More larger RCT's are needed to draw firmer conclusions.

Convolutional neural networks for the automatic segmentation of lumbar paraspinal muscles in people with low back pain.

The size, shape, and composition of paraspinal muscles have been widely reported in disorders of the cervical and lumbar spine. Measures of size, shape, and composition have required time-consuming and rater-dependent manual segmentation techniques. Convolutional neural networks (CNNs) provide alternate timesaving, state-of-the-art performance measures, which could realise clinical translation. Here we trained a CNN for the automatic segmentation of lumbar paraspinal muscles and determined the impact of CNN architecture and training choices on segmentation performance. T2-weighted MRI axial images from 76 participants (46 female; age (SD): 45.6 (12.8) years) with low back pain were used to train CNN models to segment the multifidus, erector spinae, and psoas major muscles (left and right segmented separately). Using cross-validation, we compared 2D and 3D CNNs with and without data augmentation. Segmentation accuracy was compared between the models using the Sørensen-Dice index as the primary outcome measure. The effect of increasing network depth on segmentation accuracy was also investigated. Each model showed high segmentation accuracy (Sørensen-Dice index ≥ 0.885) and excellent reliability (ICC2,1 ≥ 0.941). Overall, across all muscles, 2D models performed better than 3D models (p = 0.012), and training without data augmentation outperformed training with data augmentation (p < 0.001). The 2D model trained without data augmentation demonstrated the highest average segmentation accuracy. Increasing network depth did not improve accuracy (p = 0.771). All trained CNN models demonstrated high accuracy and excellent reliability for segmenting lumbar paraspinal muscles. CNNs can be used to efficiently and accurately extract measures of paraspinal muscle health from MRI.

Recovery expectations of neck pain patients do not predict treatments outcome in manual therapy.

Patient recovery expectations can predict treatment outcome. Little is known about the association of patient recovery expectations on treatment outcome in patients with neck pain consulting a manual therapist. This study evaluates the predictive value of recovery expectations in neck pain patients consulting manual therapists in the Netherlands. The primary outcome measure 'recovery' is defined as 'reduction in pain and perceived improvement'. A prospective cohort study a total of 1195 neck pain patients. Patients completed the Patient Expectancies List (PEL) at baseline (3 item questionnaire, score range from 3 to 12), functional status (NDI), the Global Perceived Effect (GPE) for recovery (7-points Likert scale) post treatment and pain scores (NRS) at baseline and post treatment. The relationship between recovery expectancy and recovery (dichotomized GPE scores) was assessed by logistic regression analysis. Patients generally reported high recovery expectations on all three questions of the PEL (mean sumscores ranging from 11.3 to 11.6). When adjusted for covariates the PEL sum-score did not predict recovery (explained variance was 0.10 for the total PEL). Separately, the first question of the PEL showed predictive potential (OR 3.7; 95%CI 0.19-73.74) for recovery, but failed to reach statistical significance. In this study patient recovery expectations did not predict treatment outcome. Variables predicting recovery were recurrence and duration of pain. The precise relationship between patient recovery expectations and outcome is complex and still inconclusive. Research on patient expectancy would benefit from more consistent use of theoretical expectancy and outcome models.

Risk factors for pelvic girdle pain postpartum and pregnancy related low back pain postpartum; a systematic review and meta-analysis.

BACKGROUND: Although pelvic girdle pain postpartum and pregnancy related low back pain postpartum (combined and named PGPP in this study) have a natural favourable course, there is a subgroup of women who have persistent complaints. The objective of this study was to identify personal-, (pre)pregnancy-, obstetric-, and child related risk factors on PGPP by means of a systematic literature review and meta-analysis. METHODS: Literature searches of PubMed, EMBASE, CINAHL and Cochrane up to October 2018 were conducted. Prospective cohort studies in English or Dutch describing three or more risk factors for PGPP were included. We assessed articles for inclusion and risk of bias. Studies with high risk of bias were excluded from data extraction. Data was extracted and checked for accuracy confirming to the CHARMS-checklist. Homogeneous variables were pooled. RESULTS: Twelve full text studies were assessed. Seven studies were excluded due to high risk of bias. Data was extracted from five studies. Multivariate analysis was not possible due to heterogeneity in included risk factors as well as outcome measures on risk factor per study. Pooled univariate significant risk factors on PGPP were: a history of low back pain, pre-pregnancy body mass index >25, pelvic girdle pain in pregnancy, depression in pregnancy, and a heavy workload in pregnancy. No significant obstetric and child related risk factors were reported. CONCLUSIONS: Risk factors on PGPP have been identified. Since multivariate analysis was not possible the outcome should be treated with care, because interaction between risk factors could not be analysed.

Barriers and facilitators to ask for lower urinary tract symptoms in people with low back pain and pelvic girdle pain. A qualitative study.

BACKGROUND: Lower urinary tract symptoms (LUTS) may be a relevant comorbidity when managing people with low back or pelvic girdle pain. It is unknown how often physiotherapists inquire about LUTS, and what the potential barriers and facilitators are to inquire about LUTS in this patient population. OBJECTIVE: To explore the frequency of inquiring about LUTS, and to identify the barriers and facilitators among physiotherapists with and without additional pelvic health training to ask for LUTS in people with low back or pelvic girdle pain. DESIGN: A qualitative study using thematic analysis. METHODS: Through purposeful sampling, 29 primary care physiotherapists were interviewed (16 physiotherapists and 13 physiotherapists with additional pelvic health training). Thematic analysis was performed to identify themes regarding facilitators and barriers. FINDINGS: The frequency of inquiring about LUTS was: 'never': 10%, 'sometimes': 38%, and 'always': 52%. Four barriers were identified: (1) lack of knowledge of the physiotherapist, (2) a standardised assessment approach which did not include LUTS, (3) patient expectations assumed by the physiotherapist, and (4) social, cultural and personal barriers. Three facilitators were identified: (1) communication skills and experience of the physiotherapist, (2) education and knowledge, and (3) interprofessional consultation and referral. CONCLUSION: The majority of physiotherapists surveyed in this study regularly asked for LUTS in people with low back or pelvic pain. For when not asked, the identified barriers seem modifiable with adequate training, knowledge and skill acquisition, and sound clinical reasoning.

Comparing the range of musculoskeletal therapies applied by physical therapists with postgraduate qualifications in manual therapy in patients with non-specific neck pain with international guidelines and recommendations: An observational study.

The aim of this study is to compare Dutch usual care musculoskeletal therapy in patients with non-specific neck pain with recommendations from international clinical practice guidelines. Physical therapy is diverse, as it may consist of exercise, massage, advice, and other modalities. Physical therapists with post graduate qualifications in manual therapy (MT) may additionally apply spinal thrust manipulation or non-thrust mobilization techniques to treat neck pain. It is important that, in the absence of a Dutch clinical guideline for the treatment of patients with neck pain, musculoskeletal therapists use the available recommendations from international clinical practice guidelines when treating patients with neck pain. One updated clinical practice guideline was identified (Blanpied, 2017), a report from the Task Force on Neck Pain (Guzman et al., 2008) and the IFOMPT International Framework for Examination of the Cervical Region for potential of Cervical Arterial Dysfunction prior to Orthopaedic Manual Therapy Intervention (Rushton et al., 2014). At baseline 1193 patients are included and data with regard to pain, disability, fear avoidance, expectations and applied treatment modalities are gathered. Outcome is measured using the Global Perceived Effect questionnaire. Results show that patients with acute neck pain are treated significantly more often with manipulation compared to patients with sub-acute or chronic neck pain (p < .000) and younger patients are treated with manipulation more often than older patients (p < .000). In the presence of comorbidity, the preference of spinal manipulation seems to diminish, in favour of mobilization and exercise. Almost every patient receives multimodal therapy (94.3%) and spinal manipulation and mobilization are rarely used as a stand-alone treatment (4.5% and 0.8%). Dutch musculoskeletal therapists choose treatment strategies that correspond with recommendations from international guidelines.

Clinimetric properties of sacroiliac joint mobility tests: A systematic review.

BACKGROUND: Previous systematic reviews revealed poor reliability and validity for sacroiliac joint (SIJ) mobility tests. However, these reviews were published nearly 20 years ago and recent evidence has not yet been summarised. OBJECTIVES: To conduct an up-to-date systematic review to verify whether recommendations regarding the clinical use of SIJ mobility tests should be revised. STUDY DESIGN: Systematic review. METHOD: The literature was searched for relevant articles via 5 electronic databases. The review was conducted according to the PRISMA guidelines. COSMIN checklists were used to appraise the methodological quality. Studies were included if they had at least fair methodology and reported clinimetric properties of SIJ mobility tests performed in adult patients with non-specific low back pain, pelvic (girdle) pain and/or SIJ pain. Only tests that can be performed in a clinical setting were considered. RESULTS: Twelve relevant articles were identified, of which three were of sufficient methodological quality. These three studies evaluated the reliability of eight SIJ mobility tests and one test cluster. For the majority of individual tests, the intertester reliability showed slight to fair agreement. Although some tests and one test cluster had higher reliability, the confidence intervals around most reliability estimates were large. Furthermore, there were no validity studies of sufficient methodological quality. CONCLUSION: Considering the low and/or imprecise reliability estimates, the absence of high-quality diagnostic accuracy studies, and the uncertainty regarding the construct these tests aim to measure, this review supports the previous recommendations that the use of SIJ mobility tests in clinical practice is problematic.

Prognosis and course of pain in patients with chronic non-specific low back pain: A 1-year follow-up cohort study.

BACKGROUND: It remains unclear to what extent patients recover from chronic non-specific low back pain (NSLBP). The objective of this study was to determine (1) the course of chronic NSLBP in tertiary care and (2) which factors predicted 5- and 12-month outcomes. METHODS: This prospective study includes 1760 chronic NSLBP patients from a rehabilitation clinic (mean age 40.1 years, SD 10.6). After baseline measurement, patients followed a 2-month multidisciplinary therapy programme; evaluation took place at 2, 5 and 12 months post baseline. Recovery was defined as (1) relative recovery [30% improvement on the pain, visual analogue scale (VAS) compared with baseline] and (2) absolute recovery (VAS pain ≤ 10 mm). The multivariate logistic regression analysis included 23 baseline characteristics. RESULTS: Patient-reported intensity of back pain decreased from 55.5 (SD 23.0) at baseline to 37.0 (SD 23.8), 35.3 (SD 26.1) and 32.3 (SD 26.9) at 2-, 5- and 12-month follow-up, respectively. Younger age, back pain at baseline, no psychological/physical dysfunction (Symptom Check List-90, item 9), and higher baseline scores on the physical component scale and mental component scale of quality of life (Short Form-36) were positively associated with recovery at 5 and 12 months. At 5-month follow-up, higher work participation at baseline was also a prognostic factor for both definitions of recovery. At 12-month follow-up, having co-morbidity was predictive for both definitions. CONCLUSION: The results of this study indicate that in chronic NSLBP patients, bio-psychosocial prognostic factors may be important for clinicians when predicting recovery in back pain intensity during a 1-year period.

The psychometric properties of the PABS-PT in neck pain patients: a validation study.

OBJECTIVE: This study aims to assess the reliability and validity of the Pain Attitudes and Beliefs Scale for Physiotherapists (PABS-PT) in neck pain patients. Three research goals were formulated. (1): to reexamine the factor structure of the PABS-PT, (2) to assess the test-retest reliability of the PABS-PT and (3) to determine the construct validity of the biomedical factor of the PABS-PT. METHODS: Manual therapists (n = 272) included in this study participated in an educational upgrade program for a professional masters' degree in the Netherlands and completed the Health Care Providers' Pain and Impairment Relationship Scale and the PABS-PT. Principal Axis Factor analysis was performed and correlation coefficients were calculated. In addition, Bland and Altman plots and the smallest real difference were determined. RESULTS: We performed factor analysis on 182 questionnaires and test-rest calculations on 73 questionnaires. The principal factor analysis confirmed the existing interpretable 2-factor model of a 'biomedical treatment orientation' and a 'behavioral treatment orientation'. Test-retest reliability was 'moderate' to 'good' and construct validity for the biomedical factor was 'moderate' to 'substantial'. CONCLUSION: The PABS-PT shows a consistent factor structure and good test-retest reliability and construct validity. More research is needed to gain further insight in the interplay between implicit and explicit attitudes and the dynamics of the PABS-PT score across different body parts.

Psychometric properties of the Pain Attitudes and Beliefs Scale for Physiotherapists: a systematic review.

OBJECTIVE: Evidence suggests that care providers' attitudes influence their perception of patient characteristics and the way they manage their cases. Attitudes and beliefs of care providers can be measured with the Pain Attitude and Beliefs Scale for Physiotherapists (PABS-PT). This study evaluates the measurement properties of the PABS-PT. METHODS: Databases (PubMed-Medline, Embase, Cinahl and Pedro) were searched for studies on the development or evaluation of measurement properties of the PABS-PT. Methodological quality was assessed and rated using the COSMIN checklist and scoring system. RESULTS: Of the 139 identified publications, 10 met the selection criteria. Most of the included studies had fair to excellent methodological quality scores. Positive results were found for internal consistency, construct validity, reliability and responsiveness. No psychometric data were found for the content validity and interpretability of the PABS-PT. CONCLUSION: The PABS-PT is still in a developmental stage. Results for the psychometric properties are promising, but content validity and interpretability need more study. The relationship between implicit and explicit attitudes, and their influence on test scores, remains unclear.

Face validity and reliability of the first digital assessment scheme of pelvic floor muscle function conform the new standardized terminology of the International Continence Society.

AIMS: To test the face validity and reliability of a new digital pelvic floor muscle function (PFMF) assessment scheme that was designed on the basis of the recently standardized terminology of the International Continence Society. METHODS: Study participants comprised 41 women, age 18-85 years. Data on age and parity were obtained. Face validity of the new assessment scheme was tested by three senior and one junior pelvic physiotherapists, using the Delphi technique. PFMF of each woman was assessed four times by three specially trained pelvic physiotherapists. Examiners were blinded to parity and other findings. To test reliability, Kappa (K) was used for the dichotomous variables and Weighted Kappa (K(w)) for the items with more than two categories. RESULTS: Mean age of the women was 41 years (SD 10.5); 14 were nulliparous (34.1%), 6 primiparous (14.6%), and 21 multiparous (51.2%). The new assessment scheme showed satisfactory face validity and intra-observer reliability but low inter-observer reliability. CONCLUSIONS: The new assessment scheme based on the terminology of the ICS showed satisfactory face validity and intra-observer reliability. It can therefore be considered suitable for use in clinical practice. More detailed redefinition of the described outcome measures is necessary to improve the inter-observer reliability.

Biomechanical model study of pelvic belt influence on muscle and ligament forces.

Many patients with low back and/or pelvic girdle pain feel relief after application of a pelvic belt. External compression might unload painful ligaments and joints, but the exact mechanical effect on pelvic structures, especially in (active) upright position, is still unknown. In the present study, a static three-dimensional (3-D) pelvic model was used to simulate compression at the level of anterior superior iliac spine and the greater trochanter. The model optimised forces in 100 muscles, 8 ligaments and 8 joints in upright trunk, pelvis and upper legs using a criterion of minimising maximum muscle stress. Initially, abdominal muscles, sacrotuberal ligaments and vertical sacroiliac joints (SIJ) shear forces mainly balanced a trunk weight of 500N in upright position. Application of 50N medial compression force at the anterior superior iliac spine (equivalent to 25N belt tension force) deactivated some dorsal hip muscles and reduced the maximum muscle stress by 37%. Increasing the compression up to 100N reduced the vertical SIJ shear force by 10% and increased SIJ compression force with 52%. Shifting the medial compression force of 100N in steps of 10N to the greater trochanter did not change the muscle activation pattern but further increased SIJ compression force by 40% compared to coxal compression. Moreover, the passive ligament forces were distributed over the sacrotuberal, the sacrospinal and the posterior ligaments. The findings support the cause-related designing of new pelvic belts to unload painful pelvic ligaments or muscles in upright posture.

Biomechanical analysis of reducing sacroiliac joint shear load by optimization of pelvic muscle and ligament forces.

Effective stabilization of the sacroiliac joints (SIJ) is essential, since spinal loading is transferred via the SIJ to the coxal bones, and further to the legs. We performed a biomechanical analysis of SIJ stability in terms of reduced SIJ shear force in standing posture using a validated static 3-D simulation model. This model contained 100 muscle elements, 8 ligaments, and 8 joints in trunk, pelvis, and upper legs. Initially, the model was set up to minimize the maximum muscle stress. In this situation, the trunk load was mainly balanced between the coxal bones by vertical SIJ shear force. An imposed reduction of the vertical SIJ shear by 20% resulted in 70% increase of SIJ compression force due to activation of hip flexors and counteracting hip extensors. Another 20% reduction of the vertical SIJ shear force resulted in further increase of SIJ compression force by 400%, due to activation of the transversely oriented M. transversus abdominis and pelvic floor muscles. The M. transversus abdominis crosses the SIJ and clamps the sacrum between the coxal bones. Moreover, the pelvic floor muscles oppose lateral movement of the coxal bones, which stabilizes the position of the sacrum between the coxal bones (the pelvic arc). Our results suggest that training of the M. transversus abdominis and the pelvic floor muscles could help to relieve SI-joint related pelvic pain.

The active straight leg raising test (ASLR) in pregnant women: differences in muscle activity and force between patients and healthy subjects.

Pregnancy-related low back and pelvic pain (PLBP) is a frequent complication of pregnancy. Although pathological mechanisms underlying PLBP are obscure, dysfunction of the sacroiliac joints (SI-joints) seems to play an important role. A cross-sectional study was performed on 24 pregnant women with and without PLBP. The objective was to determine muscle activation patterns of trunk and leg muscles during the active straight leg raising test (ASLR) and static hip flexion, and to determine maximal hip flexion force at 0 and 20 cm leg raise height. Moreover, the effort to raise the leg was scored. The measurements resulted in several significant differences between the patients and healthy controls; among others (a) patients scored subjectively more effort during ASLR, (b) at both 0 and 20 cm leg raise height patients had less hip flexion force, and (c) patients developed more muscle activity during ASLR. Since pregnant women with PLBP developed a higher muscle activity during ASLR with a significantly lower output at 0 and 20 cm than healthy pregnant women, it could be proposed that the ASLR demonstrates a disturbed load transfer across the SI-joints in this population.

The sacroiliac part of the iliolumbar ligament.

The iliolumbar ligament has been described as the most important ligament for restraining movement at the lumbosacral junction. In addition, it may play an important role in restraining movement in the sacroiliac joints. To help understand its presumed restraining effect, the anatomy of the ligament and its orientation with respect to the sacroiliac joints were studied in 17 cadavers. Specific dissection showed the existence of several distinct parts of the iliolumbar ligament, among which is a sacroiliac part. This sacroiliac part originates on the sacrum and blends with the interosseous sacroiliac ligaments. Together with the ventral part of the iliolumbar ligament it inserts on the medial part of the iliac crest, separate from the interosseous sacroiliac ligaments. Its existence is verified by magnetic resonance imaging and by cryosectioning of the pelvis in the coronal and transverse plane. Fibre direction, length, width, thickness and orientation of the sacroiliac part of the iliolumbar ligament are described. It is mainly oriented in the coronal plane, perpendicular to the sacroiliac joint. The existence of this sacroiliac part of the iliolumbar ligament supports the assumption that the iliolumbar ligament has a direct restraining effect on movement in the sacroiliac joints.

Insufficient lumbopelvic stability: a clinical, anatomical and biomechanical approach to 'a-specific' low back pain.

SUMMARY. A clinical, anatomical and biomechanical model is introduced based on the concept that under postural load specific ligament and muscle forces are necessary to intrinsically stabilize the pelvis. Since load transfer from spine to pelvis passes through the sacroiliac (SI) joints, effective stabilization of these joints is essential. The stabilization of the SI joint can be increased in two ways. Firstly, by interlocking of the ridges and grooves on the joint surfaces (form closure); secondly, by compressive forces of structures like muscles, ligaments and fascia (force closure). Muscle weakness and insufficient tension of ligaments can lead to diminished compression, influencing load transfer negatively. Continuous strain of pelvic ligaments can be a consequence leading to pain. For treatment purposes stabilization techniques followed by specific muscle strengthening procedures are indicated. When there is a loss of force closure, for instance in peripartum pelvic instability, application of a pelvic belt can be advised. Copyright 1998 Harcourt Publishers Ltd.

The function of the long dorsal sacroiliac ligament: its implication for understanding low back pain.

STUDY DESIGN: In embalmed human bodies the tension of the long dorsal sacroiliac ligament was measured during incremental loading of anatomical structures that are biomechanically relevant. OBJECTIVES: To assess the function of the long dorsal sacroiliac ligament. SUMMARY OF BACKGROUND DATA: In many patients with aspecific low back pain or peripartum pelvic pain, pain is experienced in the region in which the long dorsal sacroiliac ligament is located. It is not well known that the ligament can be easily palpated in the area directly caudal to the posterior superior iliac spine. Data on the functional and clinical importance of this ligament are lacking. METHODS: A dissection study was performed on the sacral and lumbar regions. The tension of the long dorsal sacroiliac ligament (n = 12) was tested under loading. Tension was measured with a buckle transducer. Several structures, including the erector spinae muscle, the posterior layer of the thoracolumbar fascia, the sarcotuberous ligament, and the sacrum, were incrementally loaded (with forces of 0-50 newtons). The sacrum was loaded in two directions, causing nutation (ventral rotation of the sacrum relative to the iliac bones) and counternutation (the reverse). RESULTS: Forced nutation in the sacroiliac joints diminished the tension and forced counternutation increased the tension. Tension in the long dorsal sacroiliac ligament increased during loading of the ipsilateral sacrotuberous ligament and erector spinae muscle. The tension decreased during traction to the gluteus maximus muscle. Tension also decreased during traction to the ipsilateral and contralateral posterior layer of the thoracolumbar fascia in a direction simulating contraction of the latissimus dorsi muscle. CONCLUSIONS: The long dorsal sacroiliac ligament has close anatomical relations with the erector spinae muscle, the posterior layer of the thoracolumbar fascia, and a specific part of the sacrotuberous ligament (tuberoiliac ligament). Functionally, it is an important link between legs, spine, and arms. The ligament is tensed when the sacroiliac joints are counternutated and slackened when nutated. The reverse holds for the sacrotuberous ligament. Slackening of the long dorsal sacroiliac ligament can be counterbalanced by both the sacrotuberous ligament and the erector muscle. Pain localized within the boundaries of the long ligament could indicate among other things a spinal condition with sustained counternutation of the sacroiliac joints. In diagnosing patients with aspecific low back pain or peripartum pelvic pain, the long dorsal sacroiliac ligament should not be neglected. Even in cases of arthrodesis of the sacroiliac joints, tension in the long ligament can still be altered by different structures.