ORIGINAL RESEARCH

Steps Toward the Validation of the Trendelenburg Test:

The Effect of Experimentally Reduced Hip Abductor
Muscle Function on Frontal Plane Mechanics
Karen D. Kendall, MKin, CAT(C),* Chirag Patel, MD,† J. Preston Wiley, MPE, MD,‡
Michael B. Pohl, PhD,§ Carolyn A. Emery, PhD,¶k** and Reed Ferber, PhD, CAT(C), ATC*††

Results: The median age and weight of the participants were

Objective: To investigate the validity of the Trendelenburg test 31 years (interquartile range [IQR], 22-32 years) and 73 kg (IQR,
(TT) using an ultrasound-guided nerve block (UNB) of the superior 67-81 kg), respectively. An average 52% reduction of HABD strength
gluteal nerve and determine whether the reduction in hip abductor (z = 2.36, P = 0.02) resulted after the UNB. No differences were found
muscle (HABD) strength would result in the theorized mechanical in cPD or ΔcPD (z = 0.01, P = 0.99, z = 20.67, P = 0.49, respec-
compensatory strategies measured during the TT. tively). Individual changes in biomechanics showed no consistency
Design: Quasi-experimental. between participants and nonsystematic changes across the group. One
participant demonstrated the mechanical compensations described by
Setting: Hospital. Trendelenburg.

Participants: Convenience sample of 9 healthy men. Only parti- Conclusions: The TT should not be used as a screening measure
cipants with no current or previous injury to the lumbar spine, pelvis, for HABD strength in populations demonstrating strength greater
or lower extremities, and no previous surgeries were included. than 30%BW but should be reserved for use with populations with
marked HABD weakness.
Interventions: Ultrasound-guided nerve block.
Clinical Relevance: This study presents data regarding a critical
Main Outcome Measures: Hip abductor muscle strength (percent level of HABD strength required to support the pelvis during the TT.
body weight [%BW]), contralateral pelvic drop (cPD), change in con-
tralateral pelvic drop (ΔcPD), ipsilateral hip adduction, and ipsilateral Key Words: Trendelenburg test, hip abductor muscle strength,
trunk sway (TRUNK) measured in degrees. ultrasound-guided nerve block, frontal plane mechanics
(Clin J Sport Med 2013;23:45–51)

Submitted for publication January 25, 2012; accepted May 8, 2012. INTRODUCTION
From the *Faculty of Kinesiology, Running Injury Clinic, University of Trendelenburg first described an abnormal gait pattern
Calgary, Calgary, Alberta, Canada; †Department of Radiology, Faculty
of Medicine, Foothills Medical Centre, University of Calgary, Calgary, in 1895.1 He hypothesized that the Trendelenburg gait
Alberta, Canada; ‡Faculty of Kinesiology, Sport Medicine Centre, resulted from a drop in pelvic position on the swing leg side
University of Calgary, Calgary, Alberta, Canada; §Department of as bodyweight is transferred to the opposite leg during walk-
Kinesiology and Health Promotion, School of Education, University ing. He discussed that the drop in pelvic position resulted
of Kentucky, Lexington, Kentucky; ¶Faculty of Kinesiology, University from the inability of the weight bearing hip abductor muscles
of Calgary, Calgary, Alberta, Canada; Departments of kCommunity
Health Sciences and **Pediatrics, University of Calgary, Calgary, (HABD) to keep the pelvis horizontal.1 The Trendelenburg
Alberta, Canada; and ††Faculty of Nursing, University of Calgary, Cal- Test (TT) was subsequently developed based on this theoret-
gary, Alberta, Canada. ical construct and continues to be used today in clinical
R. Ferber is supported by a Population Health Investigator Award from assessment of the lower back, pelvis, and hip,2–4 and as a func-
Alberta Innovates Health Solutions and the Workers Compensation Board
Alberta. C. Emery is supported by a Population Health Investigator tional outcome measure in orthopedic research.5,6
Award from Alberta Innovates Health Solutions and a Professorship in The TT is used to assess the functional strength of the
Pediatric Rehabilitation (Alberta Children’s Hospital Foundation), HABD,1 their ability to control frontal plane motion of the
Alberta Children’s Hospital Research Institute for Child and Maternal pelvis,1,7 and the ability of the lumbopelvic complex to trans-
Health, Faculty of Medicine. We affirm that we have no financial affili- fer load into single leg stance.2,8 Although a standard method
ation (including research funding), involvement with any commercial
organization, or conflict of interest that has a direct financial interest in to perform the test has been described for use within clinical
any matter included in this manuscript. populations,7 only a few studies have investigated Trendelen-
This study was approved by the University of Calgary Conjoint Health burg’s hypotheses.9–11
Research Ethics Board. DiMattia et al9 investigated the usefulness of the TT as
Corresponding Author: Karen D. Kendall, MKin, CAT(C), KNB230, Faculty
of Kinesiology, University of Calgary, 2500 University Dr NW, Calgary,
a screening measure for HABD using biomechanical methods.
Alberta T2N 1N4, Canada (kdkendal@ucalgary.ca). Measures of isometric HABD strength and peak ipsilateral hip
Copyright © 2013 by Lippincott Williams & Wilkins adduction angle (iHADD) were found to have weak and

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Kendall et al Clin J Sport Med  Volume 23, Number 1, January 2013

nonsignificant correlation during the TT.9 Results indicate that pelvis, or hip. Only participants who demonstrated pelvic
the TT has little relationship to isometric HABD strength with- alignment and equal leg length, as assessed by standard
in a young healthy population and that the validity of the TT as clinical methods of a Certified Athletic Therapist (KK), and 5
a screening measure for HABD strength is questionable.9 of 5 scores bilaterally on manual muscle testing of the HABD
Kendall et al10 investigated the relationship between were included in the study.13
HABD strength and the magnitude of contralateral pelvic drop An a priori sample size was estimated upon the primary
(cMPD) in nonspecific low back pain patients and controls biomechanical outcome variable, cMPD measured in degrees.
before and after a HABD strengthening program. Hip abductor Using estimates of variability from the literature14,15 (a = 0.05
muscle strength was poorly correlated to peak cMPD during and b = 0.20), it was determined that 6 participants would
the static TT for both groups.10 Despite significant increases in achieve 89% power to test the hypothesis and would provide
HABD strength, no differences in cMPD were measured,10 adequate protection from type I and II errors. All participants
suggesting that the HABD muscles may not be primarily signed an informed consent approved by the Conjoint Health
responsible for controlling frontal plane pelvic motion. Research Ethics Board.
Youdas et al11 tested the usefulness of the TT in iden-
tifying patients with hip osteoarthritis from controls using Procedures
validity indices. Despite significant differences in HABD Hip Abductor Muscle Strength
strength between the 2 groups, poor sensitivity, specificity,
and receiver operating curve values were reported.11 The The HABD strength was measured using a force
authors suggest that the TT provides “no better information dynamometer (Model 01163; Lafayette Instruments, Lafay-
than a 50:50 chance of identifying hip osteoarthritis patients ette, Indiana) based on published methods,16 which have been
from controls.”11 reported as reliable17 (Figure 1). One submaximal practice
Previous studies have generally shown that the use of trial and 3 test trials, with a 30-second rest period between
the TT is limited. These studies have sought to indirectly
determine the relationships between HABD strength and
measures of frontal plane motion. Only 1 study has sought
to directly investigate the ability of the HABD to function as
a primary frontal plane stabilizer of the pelvis.12 Henriksen
et al12 investigated the changes in mechanics after an intra-
muscular saline injection into the gluteus medius muscle.
Despite a significant reduction in muscle activity, no differ-
ences in trunk lean or pelvic drop angles were measured.12
However, the methods used in the study induced a pain
response and may have resulted in a measured antalgic gait
pattern rather than an altered frontal plane pelvic motion as
a consequence of reduced HABD function.
If a true relationship between HABD strength and changes
in hip/pelvis are to be measured, there needs to be a method of
reducing the function of the muscles without evoking a pain
response. Furthermore, to directly investigate the validity of the
TT, measurement of the compensation patterns at the pelvis and
hip specifically during the TT requires examination.
The purpose of this study was to determine whether an
ultrasound-guided nerve block (UNB) of the superior gluteal
nerve and subsequent reduction in HABD function would
result in the theorized compensatory strategies of the pelvis,
hip, and trunk measured during the TT. It was hypothesized
that after the UNB, there would be an increase in the frontal
plane motion of the pelvis (increased contralateral pelvic drop
[cPD]), hip (increased ipsilateral hip adduction), and trunk
(lateral sway) over the standing limb.

METHODS
Participants
A convenience sample including 9 healthy male
participants was recruited. Inclusion criteria were as follows:
older than 18 years, no current or previous injury to the
lumbar spine, pelvis, or lower extremities within the past FIGURE 1. Patient setup: hip abductor muscle testing using
12 months, and no previous surgery to the lumbar spine, hand held dynamometry with strap method.

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Clin J Sport Med  Volume 23, Number 1, January 2013 Steps Toward the Validation of the Trendelenburg Test

trials were completed. The average of 3 trials having a coef- standardized using a goniometer. The test position was held
ficient of variation of less than 10% were used for statistical for 30 seconds on each limb. Video recordings from the camera
analysis. All force (kg) measures from force dynamometry were digitized and 2D coordinates for the each of the markers
were converted into Newtons of force and then normalized were determined. The raw coordinates were used to calculate
using body mass. All strength testing were completed by the the frontal plane angles of the kinematic variables of interest
same tester. Intratester reliability was calculated using 5 pilot (Figures 2B, D). All digitization was completed by a single
study control participants (ICC(3,1) = 0.90 with an SEM of investigator. Digitization was completed using Vicon Motus 9.0.
0.09 Nm/kg).

Biomechanical Analysis Ultrasound-Guided Nerve Block Procedure

Two-dimensional (2D) mechanics were measured using The primary HABD muscles comprise gluteus medius,
a 60-Hz camera (Canon GL2-NTSC-3CCD, Canon Canada Inc, gluteus minimus, and the tensor fascia lata musculature.
Mississauga, Ontario) and analysis software (Vicon Motus 9.0, Through their anatomy and line of action, they play an
Vicon, Centennial, Colorado). Two-dimensional frontal plane important role in concentrically abducting the thigh, stabilizing
mechanics were chosen to measure the cPD because 2D the stance hip, and maintaining a horizontal pelvic position
methods have been shown to be an accurate method to measure during single leg stance.19 These muscles are solely innervated
frontal plane movements.18 Between-day variability in cPD dur- by the superior gluteal nerve.20 Therefore, inhibition of the
ing the TT using these methods and marker setup ranged from superior gluteal nerve should result in the inhibition of these
0.15 to 0.35 degrees.10 Eight 14-mm retroreflective markers muscles and subsequent reduction in HABD strength output.
were placed along the horizontal axis of the pelvis over the The UNB procedure was performed by an interven-
top of each posterior superior iliac spine, bilateral greater tional radiologist with assistance of a sport medicine physi-
trochanters of the femur, bilateral lateral femoral condyles, cian using an Acuson Sequoia 512 Ultrasound System
and bilateral acromion processes of the scapula (Figure 2A). (Siemens Medical Solutions USA, Inc, Mountain View,
The skin areas under each of the markers were inked to ensure California), with image capturing and Doppler color capa-
consistency of placement between baseline and postinjection bilities. The piriformis muscle, the gluteal vessels, and the
trials. A standing baseline trial and subsequent TTs were per- superior gluteal nerve were scanned using standard ultrasound
formed according to previously described methods.7 Participants imaging procedures. Under aseptic conditions, a spinal needle
were asked to place their hands on their hips and alternatively with guide was used to inject 10 mL of a 1% lidocaine
flex right and then left hip to 30 degrees, which was solution near the branching of the superior gluteal nerve along

FIGURE 2. A, Marker setup: left

acromion process (LAC), right acro-
mion process (RAC), left posterior
superior iliac spine (LPSIS), right
posterior iliac spine (RPSIS), left
greater trochanter (LGTR), right
greater trochanter (RGTR), left lateral
femoral condyle (LKNL), right lateral
femoral condyle (RKNL), right
treadmill (RTREAD), left treadmill
(LTREAD) (horizontal reference). B,
Trunk sway (TRUNK): angle sub-
tended by a line between the LAC
and RAC (level of the shoulders) and
a line between the LTREAD and
RTREAD (horizontal reference). C,
Contralateral pelvic drop (cPD):
angle subtended by a line between
the LPSIS and RPSIS (level of the
pelvis) and a line between the
LTREAD and RTREAD (horizontal
reference). D, Ipsilateral hip adduc-
tion: angle subtended by a line
between the LPSIS and RPSIS (level
of the pelvis) and a line between the
RKNL and RGTR (position of the
femur). Positive numbers indicate
contralateral pelvic drop position;
negative numbers indicate a contra-
lateral pelvic hike position.

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Kendall et al Clin J Sport Med  Volume 23, Number 1, January 2013

the fascias between the gluteus medius and minimus muscles.

TABLE 1. Summary of Strength and Kinematic Variables
The UNB was performed on the right hip for all participants.
Measured at Baseline and After UNB While Subjects Performed
Participants were monitored by the sports medicine physician the TT: Right Standing Limb
throughout the UNB procedure.
Baseline Post UNB
Median (IQR) Median (IQR)
Follow-up Testing
HABD (N/kg) 3.3 (3.0–4.0) 1.8 (1.7–2.4)*
After the UNB, participants were transported in
cPD (degrees) 0.4 (24.1–1.7)† 21.4 (23.1–0.8)†
a wheelchair to the biomechanics laboratory. The HABD
ΔcPD (degrees) 0.3 (0.2–0.5) 0.5 (20.1–1.2)†
strength and biomechanical procedures were repeated and
TRUNK (degrees) 3.0 (20.5–4.3)‡ 2.5 (0.2–7.9)
data were recorded between 17 and 35 minutes after UNB.
iHADD (degrees) 81.3 (80.5–83.8) 81.0 (79.5–82.4)
Participants remained in the laboratory and monitored until
a third measure of HABD strength confirmed a return to full *Significant reduction in strength P = 0.02.
function (100% of initial strength) between 80 and †Positive numbers indicate contralateral pelvic drop; negative numbers indicate
contralateral pelvic hike.
120 minutes after UNB. Participants reported mild pressure ‡Positive numbers indicate ipsilateral trunk sway (right); negative numbers indicate
discomfort during the UNB and no pain or discomfort while contralateral trunk sway (left).
ΔcPD, change in contralateral pelvic drop over 30-second trial; cPD, contralateral
performing the strength and biomechanical follow-up testing. pelvic drop; iHADD, ipsilateral hip adduction; HABD, hip abductor muscle strength;
TRUNK, trunk sway.
Outcome Measures
The primary variables of interest included cPD, mea-
sured as the average peak angle calculated during the 20- to showed no consistency in compensatory patterns between
25-second time interval of the TT, and the change in the participants and nonsystematic changes across the group. A
magnitude of contralateral pelvic drop (ΔcPD) measured as summary of the individual mechanical compensation patterns
the difference in the average peak angles calculated during the per subject is shown in Figure 4. Only subject 3 demonstrated
5- to 10-second and 20- to 25-second time intervals of the TT. the mechanical compensation patterns described by Trende-
Other variables of interest included average peak angles of lenburg: increased cPD, increased ipsilateral TRUNK, and
iHADD and trunk sway (TRUNK) angle measured during the increased iHADD (Figure 4). Because of the individual var-
20- to 25-second time intervals of the TT. iation in the mechanical compensation patterns, a post hoc
analysis on changes in HABD strength was completed using
Analysis %BW (Table 2). Subject 3 dropped to 4.6% HABD strength
The test sample size was small (n = 9), and data were post UNB, whereas the remainder of the participants ranged
not normally distributed. Thus, nonparametric statistics were between 17.1% and 25.2%.
used for analyses. Data sets from 2 participants were removed
before analysis because of insufficient reduction in HABD DISCUSSION
strength after the UNB procedure (17% and 23%, respec- The TT continues to be used as a functional method to
tively). The iHADD biomechanical data from 1 participant assess the ability of the HABD muscles to control frontal
was not included because of the inability to digitize the plane pelvic motion, but no study has directly tested this
greater trochanter markers. Wilcoxon signed rank tests deter- hypothesis. The current study used a novel UNB procedure to
mined differences in the primary variables of interest at a level investigate the mechanical compensations in frontal plane
of significance of 0.05. Changes in the other variables of kinematics because of the inhibition of the HABD group and
interest investigating possible mechanical compensations to test the existing theories of the TT.
after UNB were graphically depicted.

RESULTS
Seven of the 9 participants’ data were used in the anal-
ysis. The participants’ median age was 31 years (interquartile
range [IQR], 22-32) with median height of 176 cm (IQR, 168-
181) and median weight of 73 kg (IQR, 67-81). Compared
with baseline measures, the participants demonstrated a 52%
reduction of HABD strength (z = 2.36, P = 0.02) after the
UNB. A summary of the baseline and post-UNB HABD
strength and kinematic data are presented in Table 1. Despite
a significant drop in HABD strength after the UNB procedure,
no differences were found in cPD or ΔcPD (z = 0.01, P =
0.99, z = 20.67, P = 0.49, respectively). Figure 2 depicts the
varied relationship between the percent drop in HABD FIGURE 3. Scatterplot depicting the relationship between the
strength and cPD for each subject. Individual changes in drop (%) in hip abductor muscle strength from baseline and
kinematic variables after the UNB by subject in cPD, TRUNK, peak contralateral pelvic drop measured between 20 and 25
and iHADD are shown in Figure 3. After the UNB, the results seconds of the Trendelenburg test.

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Clin J Sport Med  Volume 23, Number 1, January 2013 Steps Toward the Validation of the Trendelenburg Test

FIGURE 4. Individual changes in kinematic variables

following the UNB procedure measured during the
TT (standing on the right leg): (A) cPD; (B) trunk
sway; (C) iHADD. Zero value represents the baseline
measure for all subjects.

The UNB procedure was successful in significantly the TT. Trendelenburg’s original gait observations were
reducing HABD strength. It is acknowledged that the use of based on a patient population with articular abnormalities of
a novel method rather than previously established methods the hip and severe muscular atrophy and weakness of the
could be considered a limitation of the study. However, nerve HABD group. Trendelenburg suggested that patients with
block methods are successfully used for local anesthesia during severely defective function and consequent lack of active
surgery21,22 and for rehabilitation interventions.23 In biome- hip abduction would demonstrate the increased pelvic drop
chanical research, the ability to perform a temporary nerve and ipsilateral trunk sway and result in the Trendelenburg gait
block of a specific motor nerve and subsequent inhibition of pattern.1 Participants in the current study were healthy part-
its associated musculature provides an excellent opportunity to icipants and before the UNB demonstrated 5 of 5 scores on
investigate the mechanical compensations that result. The UNB standard manual muscle tests. Even with the significant
procedure resulted in an average of 52% reduction of HABD drop in HABD strength, there were no significant changes
strength and did so without causing a pain response. In addi- in mechanics.
tion, the kinematic variables of interest measured are similar to Other studies involving the TT using healthy partic-
values previously reported in the literature.11,24,25 Thus, the ipants have found poor relationships between HABD strength
UNB procedure was considered successful in reducing HABD and iHADD9 and between HABD strength and cPD,10 which
strength and allowed for a suitable examination of the true supports the idea that the TT may only be useful if used to
kinematic changes and insight into the mechanical compensa- determine critical functionality of the HABD group when
tions that resulted during the TT. strength is severely limited. In the current study, an average
It was hypothesized that after the UNB procedure, there of 52% reduction in HABD strength was insufficient to pro-
would be a significant increase in the cPD measured during duce the frontal plane motion compensations as described by
the TT. The results of the study do not support this Trendelenburg. All these results suggest that the TT should
hypothesis. Despite the significant reduction in HABD not be used as a screening method for functional HABD
strength, no differences were found in cPD or ΔcPD during strength in healthy populations but rather only be used to

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Kendall et al Clin J Sport Med  Volume 23, Number 1, January 2013

osteoarthritis and controls. The patients were significantly

TABLE 2. Individual Values of Hip Abductor Muscle Strength
weaker than controls (36%BW vs 41%BW), respectively,
at Baseline and After UNB Calculated as %BW
but the TT was unable to detect the differences in pelvic on
Post femoral angle. The results suggest that the TT may not be
Baseline UNB Change
Subject (%BW) (%BW) (%BW) useful to discriminate between populations with values of
HABD strength greater than 30%BW and are further sup-
1 59.4 25.2 34.2
ported by the findings of the current study. Participants dem-
2 41.6 17.1 24.6
onstrating more than 17%BW post UNB did not specifically
3 23.9 4.6* 19.3
demonstrate the increased cPD as expected based upon the
5 32.7 18.5 14.2
theory driving the TT.
6 31.0 18.1 12.9
Therefore, based on the work of Youdas et al11 and our
7 33.5 24.5 9.0
findings, there is likely a critical level of HABD strength
9 33.7 22.8 10.9
needed to support a negative TT (a horizontal pelvic posi-
Change in strength presented as percent body weight (BW) was calculated as the tion). From our data, it could be suggested that individuals
difference between baseline and post UNB measures.
*Subject 3 was the only subject to exhibit the mechanical compensations as
with HABD strength less than 10%BW would be expected to
described by Trendelenburg after the UNB. demonstrate a positive TT (a drop in the contralateral pelvis).
Considering that 10%BW represents such a low quantity of
HABD strength, the use of the TT as the sole measure to
assess the ability of the HABD muscles to support frontal
screen patient populations with marked weakness to plane pelvic motion may not be appropriate.
determine critical levels of functional strength.
It was further hypothesized that after the UNB pro-
cedure, the participants would demonstrate the mechanical CONCLUSIONS
compensation patterns of a positive finding on the TT The TT as a single test to specifically assess HABD
(increased ipsilateral TRUNK and iHADD). Participants function or to identify HABD weakness is not appropriate
demonstrated no consistency in compensatory patterns but within healthy populations and populations that demonstrate
rather individual and varied responses of iHADD and TRUNK more than 30%BW HABD strength. The results suggest that
movement after significant reductions in HABD strength a critical level of HABD strength (10%BW) may be sufficient
(Figure 4). Only subject 3 demonstrated the mechanical com- to demonstrate a negative TT. However, this value represents
pensations described by Trendelenburg1 and therefore a post a low critical level of strength and indicates that the TT alone to
hoc analysis of individual values of HABD strength measured assess frontal plane stability of the pelvis may not be
before and after the UNB was completed. This analysis was appropriate. Further studies with a greater number of partic-
done to determine if a critical value of required HABD strength ipants are required to better establish this critical level of
for a negative TT could be identified. Calculations on the post- HABD strength required to support a negative TT. This
UNB strength data revealed a range of 4.6%BW to 25.2%BW. information will provide clinically relevant and quantitative
Subject 3 demonstrated the lowest HABD strength (4.6%BW) values to this longstanding subjective clinical test and better
after the UNB, whereas all other participants had strength guidelines for its use. Finally, additional research is needed to
values at least 17%BW or higher (Figure 5). understand how best to use the TT and to assess frontal plane
The study by Youdas et al11 used HABD strength cal- stability of the pelvis. Specifically, understanding the role of
culated as %BW as well as pelvic on femoral angle measured the abdominal and lumbopelvic muscles in pelvic stability and
during the TT to discriminate between patients with hip finding ways to best assess these muscle groups is needed.

FIGURE 5. Individual actual changes

in kinematics during the TT (stand-
ing on the right leg) grouped by
subject.

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Clin J Sport Med  Volume 23, Number 1, January 2013 Steps Toward the Validation of the Trendelenburg Test

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sets of data were used in the analysis. The a priori sample size test for identification of patients with hip joint osteoarthritis. Physiother
estimation was done appropriately and it was determined that 6 Theory Pract. 2010;26:184–194.
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