Changes in Innominate Tilt After Manipulation of the
Sacroiliac Joint in Patients with Low Back Pain
An Experimental Study
MICHAEL T. CIBULKA,
ANTHONY DELITTO,
and RHONDA M. KOLDEHOFF
The purposes of this study were to 1) propose a method to detect sacroiliac joint
dysfunction (SIJD), 2) test the interrater reliability of the method on a group of
patients with low back pain (LBP), and 3) document changes in innominate tilt
after manipulation of the sacroiliac joint. Criteria for SIJD were established by the
authors. Twenty-six patients with unilateral LBP were examined independently
for presence of SIJD by two examiners. Interrater agreement for presence or
absence of SIJD was found to be excellent (Cohen's Kappa = .88). Twenty of the
patients who met the criteria for SIJD were randomly assigned to an Experimental
Group (n = 10) or a Control Group (n = 10). The left and right innominate bones
of these 20 patients were measured for tilt before and after the intervention
period. The sacroiliac joint of the patients in the Experimental Group was manip-
ulated during the intervention period, whereas the patients in the Control Group
received no treatment. Data were analyzed using a mixed three-factor analysis
of variance. The data analysis revealed that the manipulation procedure resulted
not only in an altered innominate tilt of the same side but also in an equal and
opposite tilt of the opposite side (F = 67.07; df = 1,18; p < .05). The results
indicate that SIJD can be identified reliably in patients with LBP and that a
manipulative procedure purported to be specific to the sacroiliac joint changes
innominate tilt bilaterally and in opposite directions.
Key Words: Backache; Manipulation, orthopedic; Manual therapy; Sacroiliac joint.
Sacroiliac joint dysfunction (SIJD) has been hypothesized
to be a common cause of low back pain (LBP).1-3 The presence
or absence of SIJD is typically identified by two different
palpatory tests, one that reportedly detects reduced movement
and the other that identifies malalignment between the left
and right innominate bones.4 Accurate detection and subse-
quent treatment depend ultimately on the reliability and
validity of the tests used to identify SIJD.
Individual tests that are commonly used to identify SIJD
have been shown to have questionable reliability.5 Reliability
is necessary for dependability in a measure. Therefore, the
reliability of tests used to detect SIJD must either be improved
or abandoned. Two methods that have helped us improve the
reliability of SIJD tests in our clinic include 1) discussing
sources of disagreements that occur between therapists (eg,
training) and 2) combining the results of four different tests
used to confirm or deny the presence of SIJD. If these methods
can improve the reliability of tests used to detect SIJD,
physical therapists may be able to use these methods to
identify patients with SIJD.
Movement tests are used to detect reduced movement of
one sacroiliac joint when compared with the opposite side.4
Palpatory tests are also used to detect malalignment by iden-
tifying asymmetry between the left and right innominate
bones.3(p56) Four different patterns of malalignment between
the innominate bones have been described: 1) unilateral an-
terior tilt of one innominate bone,6,7 2) unilateral posterior
tilt of one innominate bone,6'7 3) bilateral antagonistic move-
ment of the innominate bones (left and right innominate tilt
in opposite directions),3(pl9),8 and 4) bilateral anterior tilt of
the innominate bones.2
Despite the frequent use of movement tests, no study has
been conducted on patients with SIJD to determine whether
or how sacroiliac joint movement is altered by treatment. In
addition, no study has been published using patients to deter-
mine the relationship between the left and right innominate
bones in SIJD. The purposes of this study were to 1) propose
a method to evaluate the presence of SIJD in patients with
LBP using a combination of clinical tests described previ-
ously,1,3,4 2) test the interrater reliability of selected tests for
SIJD on patients with LBP, and 3) document changes in the
tilt of the innominate bones in patients with SIJD after a
manipulation procedure commonly used to move the sacro-
iliac joint.
METHOD
The study was conducted in two phases (Fig. 1). Phase 1
involved the establishment of SIJD in the patient population
and the assessment of the reliability of the method used to
M. Cibulka, MHS, is Physical Therapist, St. Louis Rehabilitation and Sports
Clinic, 400 C Truman Blvd, Crystal City, MO 63019 (USA).
A. Delitto, MHS, is Instructor, Program in Physical Therapy, Washington
University Medical School, and Consulting Physical Therapist, Irene Walter
Johnson Rehabilitation Institute, PO Box 8083, 660 S Euclid Ave, St. Louis,
MO 63110.
R. Koldehoff, BS, is Physical Therapist, St. Louis Rehabilitation and Sports
Clinic.
This article was submitted September 22, 1987; was with the authors for
revision eight weeks; and was accepted March 15, 1988. Potential Conflict of
Interest: 4.
Volume 68 / Number 9, September 1988 1359
establish the presence or absence of SIJD. Only patients with
SIJD were included in Phase 2.
Subjects
Twenty-six patients referred to our clinic for treatment of
LBP of nonspecific origin initially participated in this study.
Criteria for exclusion included pregnancy; diagnosis of anky-
losing spondylitis; and presence of neurological signs such as
anesthesia, absence of deep tendon reflexes, profound muscle
weakness, and straight leg raise of less than 45 degrees. In
addition, patients were excluded if they exhibited signs and
symptoms consistent with symptom magnification as de-
scribed by Waddell et al.9 All patients complained of LBP of
sufficient degree to seek medical intervention. The pain in all
patients was localized to the lumbar area and occasionally to
the buttock area. No patient had pain below the knee.
Phase 1
Establishing sacroiliac joint dysfunction. After receiving
informed consent from all patients, each patient was assessed
independently by two examiners (M.T.C. and R.M.K.) for
the presence or absence of SIJD. We defined SIJD as being
present in a patient if at least three of four tests commonly
used to evaluate SIJD were positive. These tests were the
standing flexion test, the prone knee flexion test, the supine
long sitting test, and palpation of posterior superior iliac spine
(PSIS) heights for asymmetry on sitting.
Measurement of sacroiliac joint dysfunction. The first clin-
ical test used to evaluate the presence or absence of SIJD was
the standing flexion test.1,4 The standing flexion test is de-
signed to detect abnormal movement in the sacroiliac joints.
This test was only used to determine whether a patient had
SIJD. In this test, the patient stood with feet 30.5 cm apart.
The examiner's (M.T.C. or R.M.K.) thumbs were placed on
the inferior slope of the PSISs. The patient was then asked to
forward bend slowly and completely. A positive test existed
when one of the PSISs moved cranially more than the opposite
PSIS. The side that moves more cranially is purported to be
the hypomobile side.1,4
The prone knee flexion test was used to assess both abnor-
mal movement and malalignment in SIJD.1,4 The prone knee
flexion test was performed with the patient positioned prone
on a treatment table with the head in the midline position
and his shoes on. The therapist stood at the foot of the table
and grasped the patient's shoes with the thumbs passing over
the heels of the shoes. The shoes were approximated, and the
relative lengths of the lower extremities were compared by
inspecting the heels of the shoes. The patient's knees were
then flexed to 90 degrees, and any change in the length of the
lower extremities was noted. A positive test resulted when an
observable change occurred between prone leg length and
prone knee flexion leg length in either leg. A negative test
resulted when no change in lower extremity leg length oc-
curred from the prone to the knee-flexed position. If a positive
test was found, the patient was also evaluated to determine
direction of innominate tilt. A posterior tilt of the innominate
bone is characterized by a relative shortening of the lower
extremity in the prone-lying position as compared with rela-
tive lengthening on knee flexion coupled with a positive
standing flexion test on that side. Conversely, an anterior tilt
of the innominate bone is characterized by a relative length-
ening of the lower extremity in the prone-lying position as
REFERRED WITH
LOW BACK PAIN
PHASE 1
ASSESSED FOR
PRESENCE OF SIJD
IF NO SLID,
EXCLUDED FROM
PHASE 2
IF SIJD,
ENTER IN
PHASE 2
Fig. 1. Diagram of the general flow of the study. Interrater agree-
ment of presence or absence of sacroiliac joint dysfunction (SIJD)
was assessed in Phase 1. When the examiners were in agreement
concerning the presence of SIJD, the patient was assigned to Phase
2 of the study.
compared with relative shortening on knee flexion. A positive
prone knee flexion test will presumably reflect SIJD.1,4
The supine long sitting test was also used to assess abnormal
movement and malalignment in SIJD.1,4 The supine long
sitting test was performed with the patient positioned supine.
The examiner placed his thumbs under the inferior border of
each medial malleolus. The two medial malleoli were then
brought together for comparison. The patient sat up with
extended knees, and the relative length of the malleoli were
reassessed. A positive test was considered to be an observable
change in leg length between the two positions. As in the
prone knee flexion test, the lengthening or shortening of the
left and right side is relative, and a positive test is reflective of
SIJD.1,4
Palpation of the patient's PSISs in the sitting position was
also performed to help confirm SIJD and to help determine
the direction of innominate tilt.3(p56) An inequality of PSISs
on sitting is indicative of SIJD.3(p56) The patient sat on a flat
surface, and the PSISs were evaluated by placing each thumb
under the PSISs and then observing for symmetry. An uneven
height of one PSIS as compared with the other PSIS confirmed
the presence of SIJD. The side where the PSIS was low, when
compared with the opposite side, suggests that the innominate
bone was tilted posteriorly.3(p56)
Reliability. Intertester reliability was defined by the level of
agreement (beyond chance agreement) between the two ex-
aminers' independent classifications of patient status. Cohen's
Kappa statistic10 was used to assess level of agreement.
Phase 2
Of the 26 patients who agreed to participate in Phase 1, 20
(13 male, 7 female) were found to have SIJD after examina-
tion by both investigators (M.T.C. and R.M.K.), and were
subsequently admitted to Phase 2 of the study. These 20
patients were then randomly and independently assigned to
either a Control Group (n = 10) or an Experimental (manip-
ulation) Group (n = 10). The mean age of patients who
participated in Phase 2 was 26 ± 1 1 years (range = 15-47
years).
Measurement of innominate tilt. An inclinometer was as-
sembled to measure left and right innominate tilt in degrees
(Fig. 2). The instrument was fashioned after the one described
by Pitkin and Pheasant.8 Intratester reliability of this device
has been shown to be "excellent" when assessed on one day
(r =.84).11
1360 PHYSICAL THERAPY
RESEARCH
Fig. 2. Inclinometer used to measure unilateral innominate tilt.
The method for measuring innominate tilt was determined
as follows. Two therapists (M.T.C. and R.M.K.) performed
the measurements. One measurer (R.M.K.) located and spot-
ted the landmarks, and the other physical therapist (M.T.C.)
obtained the actual measurement of innominate tilt. The
anterior superior iliac spine (ASIS) and the PSIS were located,
and a 1.5-cm round marker was placed over the centers of
both the ASIS and PSIS. The patient was then asked to stand
with knees straight, feet pointing forward and 30.5 cm apart.
The investigator then placed one tip of the calipers on the
ASIS and the other tip of the calipers on the ipsilateral PSIS
and then read the amount of innominate tilt (angle of incli-
nation) off the protractor. A zero-degree measurement (a
neutral measurement) on the inclinometer denoted that if an
imaginary line connected the ASIS and PSIS, the line would
be horizontal. Positive degrees were used to describe an an-
terior innominate tilt, and negative degrees were used to
describe a posterior innominate tilt.
Four measurements from each innominate bone were taken
both before and after a treatment period. The four measure-
ments were averaged to obtain a value used to evaluate the
effect of manipulation on innominate tilt. The examiner who
obtained the actual measurements was unaware of which
patients received the manipulation.
Treatment. The patients in the Control Group received no
treatment during the treatment period, whereas the sacroiliac
joint of patients in the Experimental Group was manipulated
on the opposite side of the positive standing flexion test, using
a technique described by Stoddard.12 The patient is positioned
supine in a side-bent position with the convexity toward the
therapist. The patient's upper trunk is rotated toward the
therapist, and a posterior force is applied to the contralateral
(with reference to the therapist) ASIS. We used this technique
because it usually eliminates SIJD in one treatment session.
The side to be manipulated was always the side corresponding
to the lowest value (most negative) obtained with the calipers.
Data Analysis
The average measurements of the innominate tilt obtained
from each patient were summarized using descriptive statistics
and were analyzed with a three-way analysis of variance
(ANOVA) using a mixed factorial design (2 x 2 x 2).13 Factor
A consisted of the between-groups factor (Control Group vs
Experimental Group). Factor B was a repeated-measures fac-
tor and consisted of manipulated versus nonmanipulated side
of the pelvis. Factor C was a repeated-measures factor and
consisted of pretest versus posttest measurements. For signif-
icant two- or three-way interactions, further analysis of simple
main effects (F-ratio tests) was performed using the same
computer program. Results were considered significant at the
.05 level.
RESULTS
Results of the reliability assessment revealed a Cohen's
Kappa of .88. Obtaining a Cohen's Kappa this high in a
clinical test is considered excellent clinical agreement accord-
ing to Feinstein.14 Table 1 summarizes measurements of
innominate tilt before and after the treatment period in the
Experimental and Control Groups. The ANOVA (Tab. 2)
revealed a significant main effect with factor B and a signifi-
cant two-way interaction between manipulated and nonma-
nipulated sides (factor B) and before and after treatment
(factor C). These results, however, are precluded by the sig-
nificant three-way (A × B × C) interaction (F = 67.07; df =
1,18; p < .05). The results of the simple main effects analyses
show that the manipulative technique, which was always
performed on the innominate bone side with the most nega-
tive angle with respect to the horizontal plane, changed the
TABLE 1
Means and Standard Deviations (in Degrees) of Innominate
Bone Measurements in Experimental and Control Groups Before
and After Treatment Period
Group
Control
Experimental
Side with Most
Negative Anglea
Pretest Posttest
s s
-4.0 3.5 -3.2 4.5
-4.9 7.2 1.0 6.6
Side with Least
Negative Angle
Pretest Posttest
s s
7.1 3.4 6.9 3.8
6.3 6.4 1.0 6.6
a Manipulation was always performed on the side with the most
negative angle with respect to the horizontal plane.
Volume 68 / Number 9, September 1988 1361
TABLE 2
Results of Three-way Analysis of Variance Using a Mixed
Factorial Design (2 x 2 x 2)
Source
Factor Aa
Error (A)
Factor Bb
A x B
Error (B)
Factor Cd
A x C
Error (C)
B x C
A x B x C
Error (B x C)
df
1
18
1
1
18
1
1
18
1
1
18
SS
14.45
1885.50
1312.20
125.00
230.80
1.80
0.00
9.20
186.05
130.05
34.90
MS
14.45
104.75
1312.20
125.00
12.82
1.80
0.00
0.51
186.05
130.05
1.94
F
0.14
102.34c
9.75c
3.52
0.00
95.96c
67.07c
angle of the pelvis on the side to a more positive value (F =
24.46; df = 1,18; p < .05). Concomitant with this change on
the manipulated side was an opposite and almost equal change
in the innominate tilt of the nonmanipulated side, from a
more positive to less positive value (F = 161.74; df = 1,18; p
< .05). The differences in pretest and posttest measurements
of innominate tilt in the Control Group were not significant.
These results are summarized in Figure 3.
DISCUSSION
Analyzing only one test at a time, Potter and Rothstein
have shown a lack of reliability of tests used to measure SIJD.5
Although unreliable measures can lead to high observer vari-
ability, it is unlikely that a clinician will base an entire
assessment of a patient on one test alone.15 Instead, the
clinician depends on a battery of tests to rule out or confirm
a clinical diagnosis such as SIJD. We have shown that using
predetermined combinations of four of the same tests used
individually by Potter and Rothstein5 was reliable between
two investigators in diagnosing SIJD as defined in this study.
A diagnoses-based combination of many tests increases the
specificity of any test.16 In addition, the investigators in this
study trained using a prescribed methodology. Perhaps this
additional training added to the reliability of these measures.
A manipulative technique specific to a unilateral sacroiliac
joint created a significant change in innominate tilt bilaterally
in all of the patients in the Experimental Group. The results
of this study have shown that if the more posteriorly rotated
of the innominate bones is manipulated, the inclination of
this innominate bone will change in a more positive (anterior)
direction concomitant with an opposite change (posterior
tilting) of the opposite innominate bone. No change in innom-
inate tilt, however, was recorded in 9 of the 10 patients in the
Control Group. This result disconfirms the belief that the
manipulative technique used in this study is specific only to
the side manipulated. This result also confirms the suspicion
of an expert in the area of SIJD (Richard E. Erhard, unpub-
lished data, May 1987) that the manipulative technique results
in a bilateral effect.
The movement test (standing flexion test) was only used to
confirm or deny the presence of SIJD. We could not find a
reliable and valid method of monitoring sacral position and
motion. Knowing the position of the sacrum in relation to
Fig. 3. Pelvic tilt (in degrees relative to horizontal plane) of side with
least negative angle of Control Group (LC), side with least negative
angle of Experimental Group (LE), side with most negative angle of
Control Group (MC), and side with most negative angle of Experi-
mental Group (ME), both before and after treatment. Manipulative
technique was always applied to the sacroiliac joint of the side with
the most negative angle.
both innominate bones would allow the clinician to determine
whether the manipulative technique had a bilateral effect on
the sacroiliac joints. Future studies are needed of sacroiliac
joint movement and its relation to sacral position in patients
with SIJD.
The relationship between innominate tilt and muscle im-
balance leading to LBP has been hypothesized elsewhere.17
The results of this study suggest that treatments designed to
primarily affect unilateral inn