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. Author manuscript; available in PMC: 2024 May 1.
Published in final edited form as: Physiother Theory Pract. 2022 Jan 24;39(5):1016–1023. doi: 10.1080/09593985.2022.2030446

Clinical utility of the Trendelenburg Test in people with multiple sclerosis

Paul W Kline a,b,c, Cory L Christiansen a,b, Dana L Judd a, Mark M Mañago a,b,d
PMCID: PMC9536282  NIHMSID: NIHMS1838181  PMID: 35073816

Abstract

Background:

The clinical utility of the Trendelenburg Test remains unknown in people with multiple sclerosis (MS).

Objective:

To measure (1) intra-rater reliability, (2) agreement of goniometer-assessed Trendelenburg pelvis-on-femur angle (POF) with motion capture, and (3) concurrent validity of Trendelenburg POF and hip abduction strength with POF during walking and step negotiation.

Methods:

Trendelenburg POF was measured in 20 people with MS using goniometry and motion analysis. In addition, peak POF was measured using motion analysis during walking, step ascent, and step descent. Intra-rater reliability of goniometer-assessed Trendelenburg POF and agreement with motion analysis-assessed POF were analyzed. Pearson’s r was used to determine the relationships between Trendelenburg POF and hip abduction strength with peak POF during each functional activity.

Results:

Goniometer-assessed Trendelenburg POF demonstrated very strong reliability (ICC: 0.948), strong agreement with 3D motion analysis (ICC: 0.792), correlated moderately with peak POF during walking (r = 0.519) and step ascent (r = 0.572), and weakly with step descent (r = 0.463). Hip abductor strength correlated weakly with peak POF during step ascent (r = −0.307) and negligibly during walking (r = −0.270) and step descent (r = −0.249).

Conclusions:

Goniometer-assessed Trendelenburg POF was reliable, agreed with motion analysis, and may provide insight into hip abduction muscle performance during functional activities in people with MS.

Keywords: Multiple sclerosis, Trendelenburg, hip abduction strength, pelvis, psychometrics

Introduction

Multiple sclerosis (MS) is an autoimmune-mediated neurological disease affecting over 2.5 million people worldwide (Compston and Coles, 2008). MS causes inflammatory demyelination in the central nervous system, which over time results in neurodegeneration and progressive disability (Compston and Coles, 2008). MS can cause a plethora of symptoms, but those that affect functional mobility are particularly important as functional mobility limitations are a key driver of lower levels of physical activity, more advanced disability, and decreased quality of life (Backus, 2016; Motl, 2010). Hip abduction strength and frontal plane pelvis motion are key contributors to functional mobility for people with MS and are correlated with greater disability, poor standing balance, recurrent falls, increased unsteadiness during gait, and reduced walking and stair climbing abilities (Citaker et al., 2013; Kasser et al., 2011; Kline et al., 2021; Mañago et al., 2020; Mañago, Hebert, Kittelson, and Schenkman, 2018a; Mañago, Kline, Alvarez, and Christiansen, 2020; Morel et al., 2017; Psarakis et al., 2018; Ramari, Hvid, David, and Dalgas, 2020). For these reasons, improvement of hip abduction muscle performance and frontal plane pelvis control are potential targets for rehabilitation intervention (Arntzen et al., 2020; Mañago, Hebert, Kittelson, and Schenkman, 2018b; Padgett and Kasser, 2013). However, there is a lack of evidence justifying the clinical utility of assessment tools for evaluating hip abduction muscle performance and frontal plane pelvis control in people with MS, limiting the ability of clinicians to reliably identify these impairments and monitor progress with intervention.

Clinically, hip abduction strength can be assessed reliably using hand-held dynamometry (HHD) (Mañago, Hebert, and Schenkman, 2017); however, this is commonly performed in a non-weight bearing position (Thorborg, Petersen, Magnusson, and Hölmich, 2010). While peak hip abduction strength measured in sidelying has been shown to correlate with walking speed and endurance, single-leg balance, and fall risk in people with MS (Citaker et al., 2013; Kasser et al., 2011; Mañago, Hebert, Kittelson, and Schenkman, 2018a) the hip abductors are most active during gait while in the weight-bearing position of stance phase (Semciw, Pizzari, Murley, and Green, 2013). However, people with MS commonly present with deficits in motor coordination that may limit frontal plane pelvic stability despite sufficient hip abductor strength (Plotnik et al., 2020; Richmond, Swanson, Peterson, and Fling, 2020). Therefore, it is important to investigate clinical assessments that measure frontal plane pelvic stability in weight-bearing positions in people with MS as this may provide additional clinical insight into gait and other functional mobility task performance that is unexplained by isolated hip abductor muscle strength testing.

The Trendelenburg Test is a clinical assessment, which measures frontal plane pelvic stability in weight-bearing while standing on one leg (Hardcastle and Nade, 1985). While the definition of a positive test can vary (Asayama, Naito, Fujisawa, and Kambe, 2002; Hardcastle and Nade, 1985; Westhoff et al., 2006) a drop of the contralateral anterior superior iliac spine (ASIS) below the level of the ASIS of the stance limb in the frontal plane may indicate impairments in frontal plane pelvic stability (Bailey, Selfe, and Richards, 2009). More specifically, the frontal plane pelvic stability of the stance limb can be quantified during the Trendelenburg Test by measuring the frontal plane angle formed by the pelvis relative to the femur (pelvis-on-femur angle [POF]) (Hardcastle and Nade, 1985; Youdas, Madson, and Hollman, 2010). The Trendelenburg Test has been studied in a variety of orthopedic conditions (Bailey, Selfe, and Richards, 2009; Kendall et al., 2013; Youdas, Madson, and Hollman, 2010; Youdas et al., 2007); however, the clinical utility of the test, reliability, and validity of quantifying POF during the Trendelenburg Test are unknown in people with MS. Given the myriad of muscle strength and motor control deficits present in people with MS, Trendelenburg Test POF quantified via goniometry has potential clinical utility as an assessment tool beyond that of isolated hip abductor muscle strength assessment. However, a systematic assessment of the clinical utility of this assessment method in people with MS is lacking. The purpose of this study was to evaluate the clinical utility of the Trendelenburg Test in people with MS. Clinical utility was evaluated by determining (1) reliability and agreement of goniometer-assessed POF with laboratory-based 3D motion capture analysis during the Trendelenburg Test and (2) concurrent validity of the Trendelenburg Test POF and hip abduction muscle strength with POF during walking, step ascent, and step descent was determined. We hypothesized that Trendelenburg POF measured via goniometry would have strong reliability and agreement with gold-standard motion capture analysis, and that Trendelenburg POF measured via goniometry would positively correlate with peak POF during walking, step ascent, and step descent tasks.

Methods

This was a cross-sectional observational study involving 20 people with MS. Adults (ages 18–65) with a neurologist-confirmed diagnosis of MS and ability to ambulate 100 m without an assistive device were included (Kurtzke, 1983). Potential participants were excluded if they: changed their MS disease-modifying therapies within the past month; had a neurologist-confirmed MS exacerbation in the past month; or presented with greater than minimal spasticity (Modified Ashworth Scale ≥2) (Bohannon and Smith, 1987). All participants signed an informed consent approved by the Colorado Multiple Institutional Review Board. All testing took place in a human performance laboratory at the Department of Physical Medicine and Rehabilitation, University of Colorado.

MS-related disability was measured using the standard Kurtzke Expanded Disability Status Scale (EDSS) (Kurtzke, 1983), where an EDSS score <6.0 signifies the ability to walk independently without an assistive device for at least 100 m. A licensed physical therapist with standardized EDSS assessment training collected all EDSS data. Descriptive characteristics of age, height, weight, sex, and time since diagnosis were also recorded for each participant.

To measure the POF during the Trendelenburg Test, participants were standing, and were asked to raise one leg off the ground using a combination of hip and knee flexion, but no more than approximately 30° of hip flexion to allow for alignment of the goniometer with the ASIS (Hardcastle and Nade, 1985; McCarney et al., 2020). Participants were allowed handheld assistance using free-standing balance poles as needed to obtain the position (Figure 1). Due to balance impairments commonly observed in people with MS, instead of asking participants to maximally elevate the pelvis during the Trendelenburg Test, participants were asked to maintain a level pelvis with the trunk vertical and approximately above the center of the pelvis and stand on one leg for up to 30 s. Light finger touch on bilateral balance poles was allowed if necessary for subtle balance corrections during the Trendelenburg Test. The POF was measured using goniometry and a 3D motion analysis system simultaneously. The goniometer assessor verbally indicated when the final measurement was taken with the goniometer in order for the motion analysis operator to tag and sync the 3D motion analysis capture with the goniometer assessment. For goniometry, a standard goniometer was used to assess the POF using bilateral anterior superior iliac spines and the center of the patella of the stance limb as alignment landmarks. All goniometer assessments were performed by a licensed physical therapist. The POF was measured with the axis of the goniometer placed on the ASIS of the stance limb, with the goniometer arms aligned with the contralateral ASIS and center of the patella of the stance limb and was documented when the contralateral ASIS was at its lowest point during the final 3 s of the Trendelenburg Test. For 3D motion analysis, an eight-camera, motion analysis system (Vicon Motion Systems, Oxford, UK) recorded the pelvis (7 markers) and thigh (4 markers) segments with a sampling rate of 100 Hz and a marker set described in full detail in a previous study (Murray, Gaffney, Davidson, and Christiansen, 2017). The POF measured with 3D motion analysis was also documented as the frontal plane angle (Y-plane) between the pelvis and thigh segment of the stance limb when the contralateral ASIS was at its lowest point (Figure 2). In order to standardize this measurement between assessment methods, the observed POF was subtracted from 90° representing a horizontal pelvis and vertical femur for both goniometry and motion capture measurements. Participants performed three Trendelenburg Tests on each limb with a brief (30 s) rest between trials. All trials (n = 120, three from each limb of each participant) were used to determine reliability of goniometry-assessed Trendelenburg POF, minimal detectable change, and agreement between the two methods. The mean of the participants’ three trials from each limb was used for the concurrent validity analyses.

Figure 1.

Figure 1.

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Participant positioning for Trendelenburg Test.

Figure 2.

Figure 2.

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Representation of pelvis-on-femur angle during overground walking, defined as the frontal plane angle between the pelvis and thigh segment of the stance limb when the contralateral ASIS was at its lowest point.

In addition to the Trendelenburg Test, POF was measured using 3D motion analysis, while subjects completed overground walking at their self-selected speed, and ascent and descent of a 15.2 cm step. All participants performed three walking trials at their self-selected normal walking speed and completed three single-step ascents and descents leading with each limb. Gait speed was monitored during motion capture analysis using motion-activated sensors set 5 m apart in the center of the 12-m walkway, and only trials within ± 5% of the mean self-selected gait speed were used for analysis. For the step ascent task, participants began in front of the step and were instructed to ascend and come to rest at the top of the step. For the step descent task, participants began at the top of the step and were instructed to descend the step and come to rest on the ground.

Lastly, peak hip abduction muscle strength was measured in sidelying using hand-held dynamometry for both limbs (Lafayette Model 01165, Lafayette Instrument, Lafayette, IN, USA) (Mañago, Hebert, and Schenkman, 2017; Piva et al., 2011). Participants were positioned in sidelying with the hip in 0° of flexion, abduction, and external rotation, as previously described (Mañago, Hebert, and Schenkman, 2017). Following an accommodation trial, three maximal effort trials were performed with the dynamometer placed just proximal to the lateral malleolus, and the average of the two trials with the highest force (in kilograms) was normalized to body mass index and used for data analysis. This test has been shown to be reliable in people with MS (Mañago, Hebert, and Schenkman, 2017).

For each task with 3D motion capture analysis, marker trajectories were low-pass filtered (Butterworth fourth-order, phase lag) at 6 Hz cutoff frequencies using Visual3D, a 15-segment subject-specific model was created, and the pelvis and thigh segments were used for POF calculations (C-Motion, Germantown, MD). Joint angles were calculated using Cardan XYZ angle rotations with the distal segment referenced to the proximal segment (e.g. thigh relative to pelvis).

Means and standard deviations were calculated for all descriptive variables with the exception of EDSS scores, which were reported as median and range. A one-way random effects intraclass correlation coefficient (ICC1,1) was used to determine within-session, intra-rater reliability for Trendelenburg POF assessed by goniometry (Koo and Li, 2016). Minimal detectable change (MDC) values were calculated as MDC = z-score (95% CI) × SEM × ∏2, with SEM representing the standard error of measurement. SEM is calculated from the standard deviation (SD) of the measure and the ICC value as follows: SEM = SD × ∏(1-ICC). A two-way random effects intraclass correlation coefficient (ICC2,1) was used to determine agreement between the Trendelenburg POF’s assessed by goniometry and 3D motion analysis (Liu et al., 2016). The ICC values in both the reliability and the agreement analyses were considered to be very strong when greater than 0.90, strong from 0.75 to 0.90, moderate from 0.50 to 0.74, and poor if less than 0.50 (Koo and Li, 2016). Pearson product moment correlations (r) were used to determine concurrent validity between goniometer-assessed POF and peak hip abductor muscle strength with peak POF (3D motion analysis) during the self-selected walking, step ascent, and step descent. Correlations were considered very strong from 0.90 to 1.00, strong from 0.70 to 0.89, moderate from 0.50 to 0.69, weak from 0.30 to 0.49, and negligible if under 0.30 (McDowell, 2006). Significance of all statistical tests was set to p < .05. SPSS (Version 26, IBM, Armonk, NY, USA) was used for all analyses.

Results

Twenty people with MS were included in this study (Table 1). No patients fell during the assessment or had pain that limited their performance.

Table 1.

Participant demographics.

People with MS (n = 20)
Age (years) 48.9 ± 12.3
Height (m) 1.68 ± 0.09
Weight (kg) 69.7 ± 16.1
Body mass index (kg/m2) 24.8 ± 5.4
EDSS (median; range) 3.5; 1.5–5.5
Sex (number female; percentage) 16; 80%
Time since MS diagnosis (years) 14 ± 9.7
Overground gait speed (m/s) 1.12 ± 0.20
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Data presented as mean ± standard deviation unless otherwise noted. MS: multiple sclerosis; EDSS: Expanded Disability Status Scale.

Trendelenburg POF measured using goniometry demonstrated very strong within-session, intra-rater reliability (ICC: 0.948, 95% Cl: 0.912–0.971, p < .001) for both limbs. Goniometer-assessed Trendelenburg POF was also very strong when analyzed as left and right limbs separately (Table 2). The MDC for the Trendelenburg POF using goniometry was 2.1° for both limbs with an SEM of 0.775. Table 2 contains ICC, SEM, and MDC values for each reliability analysis.

Table 2.

Reliability and agreement results.

ICC (95% CI) SEM MDC
Reliability: All trials 0.948 (0.912–0.971) 0.775 2.1
Reliability: Left limb 0.945 (0.884–0.976) 0.833 2.3
Reliability: Right limb 0.955 (0.906–0.981) 0.687 1.9
Agreement: Goniometer to 3D motion analysis 0.792 (0.702–0.855) - -
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p < 0.001 for all comparisons. ICC: intraclass correlation coefficient; 95% CI: 95% confidence interval; SEM: standard error of measurement; MDC: minimal detectable change.

Goniometric assessment of POF during the Trendelenburg Test demonstrated strong agreement with the POF captured using 3D motion analysis (ICC: 0.792, 95% CI 0.702–0.855, p < .001) (Table 2). Mean Trendelenburg POF was 9.1 ± 3.3° (mean ± standard deviation) with goniometry and 4.1 ± 5.8° with 3D motion analysis.

Concurrent validity metrics demonstrate moderate and positive associations between the goniometer-assessed Trendelenburg POF and 3D motion analysis-assessed peak POF during overground walking (r = 0.519, p = .001) and step ascent (r = 0.572, p < .001), and weakly associated with POF during step descent (r = 0.463, p = .003) (Figure 3). Hip abductor muscle strength was weakly correlated with goniometer-assessed Trendelenburg POF (r = −0.373, p = .018) and 3D motion analysis peak POF during step ascent (r = −0.307, p = .054). Negligible associations were observed between hip abductor muscle strength and POF during walking (r = −0.270, p = .092) and step descent (r = −0.249, p = .122) (Figure 3).

Figure 3.

Figure 3.

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Scatterplots of correlations between goniometer-assessed pelvis-on-femur angle (POF) during the Trendelenburg Test and POF during (a) overground walking; (b) step ascent; and (c) step descent, and hip abduction isometric muscle strength and pelvis-on-femur angle (POF) during (d) overground walking; (e) step ascent; and (f) step descent.

Discussion

The current study supports the clinical utility of the Trendelenburg Test to assess POF in people with MS. First, we found that Trendelenburg Test POF can be reliably quantified with a standard goniometer in a clinical setting by measuring the angle formed by the anterior superior iliac spines and femur of the stance limb. Second, we demonstrated that standard goniometry had strong agreement with gold-standard 3D motion analysis in the assessment of Trendelenburg POF. Finally, we found that Trendelenburg POF was significantly correlated to POF during gait and stair tasks, while peak hip abduction isometric strength correlated significantly to POF during step ascent only. The current results suggest assessing Trendelenburg POF with a standard goniometer may be a valuable clinical tool to assess frontal plane pelvic stability in patients with MS.

The Trendelenburg Test is a commonly used clinical assessment that has demonstrated good reliability in diagnosis of hip abductor muscle dysfunction in a variety of orthopedic conditions (Asayama, Naito, Fujisawa, and Kambe, 2002; Bailey, Selfe, and Richards, 2009; Roussel et al., 2007; Westhoff et al., 2006). To our knowledge, this is the first study to assess the reliability of the Trendelenburg Test in a population with a chronic neurological condition. By implementing the Trendelenburg Test based on previously validated methods emphasizing objective measurement of POF (Asayama, Naito, Fujisawa, and Kambe, 2002; Hardcastle and Nade, 1985; Westhoff et al., 2006), we demonstrated that the test had very strong intra-rater reliability when assessed using goniometry in people with MS. A prior study using goniometry reported an MDC of 4° for Trendelenburg POF in a sample of healthy adult men and women (Youdas et al., 2007). In the current study, we identified an MDC of 2.1° (range: 1.9–2.3°) (Table 2) in our sample of adults with MS. Given that the Trendelenburg POFs observed in our sample were between 2 and 15°, an MDC of 2.1° should have sufficient sensitivity to provide clinically useful data and capture change in frontal plane pelvic stability when longitudinally evaluating people with MS by a single rater. The smaller MDC observed in the current study in comparison to a population of healthy adult men and women illustrates the need to evaluate the psychometrics of tests and measures in specific patient populations as the results may be influenced by the unique characteristics of a condition or disease.

The current study also identified strong agreement between Trendelenburg POF measured using goniometry and Trendelenburg POF determined using 3D motion analysis, further supporting the potential utility of the Trendelenburg Test. While this study supports the ability to score the Trendelenburg Test on a continuous scale using goniometry, the test is often scored dichotomously in clinical settings, with a positive test indicated by a drop of the pelvis on the non-weight bearing side, and a negative test indicated by the pelvis remaining stable and elevated in the frontal plane (Bailey, Selfe, and Richards, 2009; Hardcastle and Nade, 1985; McCarney et al., 2020). However, dichotomous rating based on visual assessment of the Trendelenburg Test POF has been shown to have weak agreement with 3D motion analysis in a sample of healthy adults (McCarney et al., 2020). Other studies have attempted to quantify the degree of frontal plane pelvic tilt necessary for a positive test. Using a motion capture analysis, angles as small as 2° (Asayama, Naito, Fujisawa, and Kambe, 2002) and up to 8° (Westhoff et al., 2006) have been suggested as a threshold for a positive test. The strong agreement between goniometer-assessed Trendelenburg POF with the same angle derived using 3D motion analysis supports the use of standard goniometry for the objective assessment of Trendelenburg POF. The ability to reliably and accurately quantify POF using goniometry, a widely available clinical tool, overcomes the large cost and equipment barriers to 3D motion capture and may aid clinicians in tracking changes in frontal plane pelvic stability. However, for people with MS, more study is needed to determine a potential threshold for a positive or negative test as well as values that indicate meaningful clinical changes in functional mobility.

Gait and stair navigation are essential daily activities in which patients with MS often report difficulty (Alzahrani, Dean, and Ada, 2009; Carpinella et al., 2018; Corporaal et al., 2013; Heesen et al., 2008; Zwibel, 2009) and prior studies show that in people with MS, hip abduction muscle strength is associated with gait speed, gait endurance, and frontal plane pelvis excursion during self-selected walking (Mañago, Hebert, Kittelson, and Schenkman, 2018a; Mañago, Kline, Alvarez, and Christiansen, 2020). The observed relationships with POF during functional activities suggest that the Trendelenburg Test may provide information about the performance of these tasks beyond that explained by hip abductor muscle strength. In the current study, the correlations between POF during walking, stair ascent, and stair descent and peak POF during the Trendelenburg Test were consistently, albeit only slightly, stronger than those with isometric hip abduction muscle strength. This may be because the Trendelenburg Test imposes eccentric demand upon the hip abductors to limit contralateral pelvic drop in a similar manner in which they are used during gait and stair tasks. In contrast, isometric hip abduction muscle strength assessment is often performed in a non-weight bearing, sidelying position that does not replicate the task demands involved with gait and stair navigation (Mañago, Hebert, and Schenkman, 2017; Thorborg, Petersen, Magnusson, and Hölmich, 2010). The Trendelenburg Test also includes components of balance and motor control not required with isometric hip abduction muscle strength testing, which may contribute to the observed pelvic drop (Bailey, Selfe, and Richards, 2009). Acknowledging that correlation is not causation, the relationship observed between Trendelenburg POF and key functional movements reinforces prior evidence that frontal plane pelvic stability is a contributor to mobility in people with MS (Kline et al., 2021; Mañago, Kline, Alvarez, and Christiansen, 2020). Furthermore, measuring Trendelenburg POF with goniometry may provide a clinically feasible method to quantify pelvic stability.

There are limitations to this study that need to be considered. We did not assess the Trendelenburg Test POF as a dichotomous test, but rather were interested in quantifying the POF attained during a single-limb stance, which makes direct comparison to prior studies difficult. In addition, we did not assess sagittal or transverse plane pelvis motion. Despite good agreement between the two methods, combined sagittal, frontal, and transverse plane motion may have resulted in the overestimation of the POF with standard goniometry (9.1 ± 3.3°) compared to 3D motion analysis (4.1 ± 5.8°). In addition, we did not quantify trunk motion. Increasing frontal plane trunk motion can be a method to compensate for frontal plane pelvic drop during the Trendelenburg Test and may have influenced the results of the current study. Although not quantified, participants were instructed to keep their trunk vertical, and this was achieved based on visual inspection. Furthermore, quantitative assessments of balance, motor control, or other factors (e.g. limb flexor weakness, ataxia, and sensory impairment) were not measured in the current study and should be taken into account in future work. Lastly, isokinetic dynamometry, the gold-standard for muscle strength assessment, was not used in this study and may have influenced the muscle strength results. Future work should also seek to establish between-session and inter-rater reliability and clinically important difference metrics for Trendelenburg POF in people with MS.

In conclusion, goniometer-assessed Trendelenburg POF is a clinically feasible tool to quantify frontal plane pelvic stability with very strong intra-rater reliability and strong agreement with frontal plane 3D motion analysis-assessed Trendelenburg POF. Measuring Trendelenburg POF using standard goniometry may provide important clinical insight into hip abductor muscle performance during walking and step negotiation in people with MS beyond that provided by isometric hip abduction strength testing alone.

Acknowledgments

This work was supported by a grant from the Department of Physical Medicine and Rehabilitation at the University of Colorado Anschutz Medical Campus and the Colorado Clinical and Translational Science Institute (NIH/NCATS UL1-TR001082, TL1-TR002535).

Footnotes

Disclosure statement

No potential conflict of interest was reported by the author(s).

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