Nijs2006

Manual Therapy 11 (2006) 69–77
Original article
Diagnostic value of five clinical tests in
patellofemoral pain syndrome$
Jo Nijsa,b,Ã, Catherine Van Geela
, Cindy Van der auweraa
, Bart Van de Veldea
a
Division Musculoskeletal Physiotherapy, Department of Health Sciences, Hogeschool Antwerpen, Belgium
b
Department of Human Physiology, Faculty of Physical Education and Physical Therapy, Vrije Universiteit Brussel (VUB), Brussel – Belgium
Abstract
The current study is aimed at examining the validity of five clinical patellofemoral tests used in the diagnosis of patellofemoral
pain syndrome (PFPS). Forty-five knee patients were divided into either the PFPS or the non-PFPS group, based on the fulfilment
of the diagnostic criteria for PFPS. An investigator, blinded to the group assignment, performed the vastus medialis coordination
test, patellar apprehension test, Waldron’s test, Clarke’s test, and the eccentric step test. The positive likelihood ratio was 2.26 for
both the vastus medialis coordination test and the patellar apprehension test. For the eccentric step test, the positive likelihood ratio
was 2.34. A positive outcome on either the vastus medialis coordination test, the patellar apprehension test, or the eccentric step test
increases the probability of PFPS to a small, but sometimes important, degree. For the remaining tests, the positive likelihood ratios
were below the threshold value of 2, indicating that given a positive test result, the probability that the patient has PFPS is altered to
a small, and rarely important degree. The negative likelihood ratios for all tests exceeded the threshold value of 0.5, suggestive of
clinically irrelevant information. These data question the validity of clinical tests for the diagnosis of PFPS.
r 2005 Elsevier Ltd. All rights reserved.
Keywords: Diagnosis; Patellofemoral; Patellofemoral pain syndrome; Validity
1. Introduction
In the absence of other pathology, anterior or
retropatellar pain which exacerbates during sustained
sitting, kneeling, ascending or descending stairs, and
squatting is defined as patellofemoral pain syndrome
(PFPS). The aetiology of PFPS has not been delineated,
but appears to be multifactorial. Abnormal tracking of
the patella, possibly inducing pain and abnormal tissue
stresses, has frequently been proposed as a contributing
factor to PFPS (Baker et al., 2002). A delayed onset of
the vastus medialis obliquus in relation to the vastus
lateralis, as observed in PFPS subjects (Cowan et al.,
2001, 2002, Tang et al., 2001), might account for the
abnormal patellar tracking. Apart from a neuromuscu-
lar imbalance of the vastii, other theories for the origin
of PFPS have been proposed (and are able to explain
maltracking of the patella): tightness of the lateral knee
retinaculum, hamstrings, iliotibial band, and gastrocne-
mius; overpronation of the subtalar joint (Tang et al.,
2001), reduced proprioceptive information (Baker et al.,
2002), and the depth of the trochlear groove (Powers,
2000). Regarding the conservative treatment strategies,
Bizzini et al. (2003) concluded from their systematic
literature review that quadriceps strengthening, acu-
puncture, the use of a resistive brace, and the combina-
tion of exercises with patellar taping and biofeedback
are effective in decreasing pain and improve functioning
in PFPS patients. In their review article, Thome´ e et al.
(1999) suggested that standardized information and
ARTICLE IN PRESS
www.elsevier.com/locate/math
1356-689X/$ - see front matter r 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.math.2005.04.002
$
The first three authors contributed equally to the present
manuscript.
ÃCorresponding author. Tel.: +32 2 477 4604; fax: +32 2 477 4607.
Department of Human Physiology, Faculty of Physical Education and
Physical Therapy, Vrije Universiteit Brussel (VUB), MFYS/Sportgen-
eeskunde, VUB KRO gebouw –1, Laarbeeklaan 101, 1090 Brussel –
Belgium
E-mail address: jo.nijs@vub.ac.be (J. Nijs).

adjusted physical activity (i.e. avoiding pain-causing
activities etc.) will suffice for many PFPS patients
having mild symptoms, while chronic PFPS subjects
(knee pain duration of at least six months) require a
specific training programme. However, at least three
systematic reviews addressing the effectiveness of
physical interventions in PFPS indicate that the evidence
is limited and that high quality randomized controlled
clinical trials are required (Zomerdijk et al., 1998;
Crossley et al., 2001; Bizzini et al., 2003).
Physical examination is essential in the diagnosis of
any medical condition, especially in musculoskeletal
disorders (Malanga et al., 2003). However, in order to
draw appropriate conclusions from the findings of the
physical examination, it is important that clinicians are
aware of the significance of the test results (i.e. the
diagnostic value of each test). A positive vastus medialis
coordination test has been suggested as an indicator of
dysfunction of the vastus medialis obliquus muscle
which may result in pain (Souza, 1997), pain or crepitus
during Waldron’s test has been proposed as a sign of
patellofemoral pain disorders (Martens et al., 1995;
Souza, 1997). Likewise, both the patellofemoral grind-
ing test and the eccentric step test have been suggested to
be indicative of PFPS (Souza, 1997; Selfe et al., 2001a;
Malanga et al., 2003). However, the scientific exami-
nations of several clinical tests of patellar position
and mobility have yet to prove them reliable (Watson
et al., 2001), and Malanga et al., (2003) concluded
from their literature review that studies documenting
the sensitivity or specificity of the patellofemoral
grinding test in the diagnosis of PFPS are essentially
lacking. Apart from one study reporting that the
eccentric step test produced knee pain in 57 of 77
PFPS patients (74%) (Selfe et al., 2001a), we are
unaware of data addressing the scientific value of
clinical tests in the diagnosis of PFPS. A study
examining the validity of the vastus medialis coordina-
tion test, patellar apprehension test, Waldron’s test, and
Clarke’s test in the diagnosis of PFPS in knee pain
patients was therefore warranted.
A number of self-assessment questionnaires, which
are aimed at assessing functionality in PFPS patients,
have been reported in the scientific literature, but their
psychometric properties have not been addressed
adequately (Bennell et al., 2002). Still, Selfe et al.
(2001a) constructed the Modified Functional Index
Questionnaire (MFIQ), and examined its reliability
and clinical sensitivity in PFPS patients (Selfe et al.,
2001b). An English questionnaire, however, cannot be
applied to subjects having Dutch as their native
language (i.e. to PFPS patients in the Flemish part of
Belgium or in the Netherlands). We therefore translated
the original MFIQ into Dutch, and examined some of
the psychometric properties of the Dutch version of the
MFIQ.
2. Purpose
The primary aim of the current study was to examine
the validity of five clinical patellofemoral tests (the
vastus medialis coordination test, patellar apprehension
test, Waldron’s test, Clarke’s test, and the eccentric step
test) used in the diagnosis of PFPS in knee pain patients.
Secondly, this study aimed at translating an existing
English self-assessment questionnaire for assessing
functionality in PFPS-patients into Dutch, and examin-
ing some of the psychometric properties (the disease-
specificity, the internal consistency, and the convergent
validity) of the scores obtained with this new assess-
ment-tool in PFPS-patients.
3. Methods
3.1. Subjects and study design
A sample of convenience of 45 knee patients was
recruited from private practices and outpatient clinics
(multicentre trial). Prior to study participation, all
patients were given both oral and written information
regarding the nature and purpose of the study. All
subjects had to give written informed consent in order to
be included in the study. The rights of the subjects were
protected, implicating that the patient was allowed to
withdraw at any time if the pain became unbearable.
Subjects were included for the trial if they experienced
knee pain, if they were referred by a physician for
physical therapy (Ng and Cheng, 2002), if they were
independent ambulators in the community (Watson et
al., 2001), and if they had not undergone knee surgery
(Cowan et al. 2001; Ng and Cheng, 2002; Laprade and
Culham, 2002; Brechter and Powers, 2002). Including
patients with scars from knee surgery would prohibit a
blinded assessment. Next, all included patients were
divided into either the PFPS or the non-PFPS group,
based on the fulfilment of the diagnostic criteria for
PFPS. The criteria used for the diagnosis of PFPS were
based on those used in other PFPS studies: patients (1)
were diagnosed as a PFPS case by a medical doctor
(Bennell et al., 2002; Ng and Cheng, 2002), (2) had
anterior or retropatellar knee pain (Bennell et al., 2002;
Brechter and Powers, 2002; Cowan et al., 2001; Watson
et al., 2001); (3) reported that at least two of the
following activities exacerbated their symptoms: pro-
longed sitting, ascending or descending stairs, squatting,
kneeling (Lepa¨ lla¨ et al., 1998; Bennell et al., 2002;
Cowan et al., 2001; Tang et al., 2001; Watson et al.,
2001; Brechter and Powers, 2002; Cowan et al., 2002;
Thome´ e et al., 2002); and (4) were not allowed to show
clinical evidence of a current knee condition other than
PFPS (Lepa¨ lla¨ et al., 1998; Bennell et al., 2002; Cowan
et al., 2001; Watson et al., 2001; Cowan et al., 2002;
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J. Nijs et al. / Manual Therapy 11 (2006) 69–7770

Laprade and Culham, 2002; Thome´ e et al., 2002).
Subjects not fulfilling all four requirements listed above
were assigned to the control group (non-PFPS knee
patients), on the premise that they did not fulfil the first
three requirements either. Patients fulfilling the first
three criteria, and having evidence of a current knee
condition other than PFPS were considered ‘co-morbid
PFPS-patients’. Since the primary aim of this study was
to examine the diagnostic value of patellofemoral tests,
co-morbid PFPS patients were excluded from the trial.
In occurrence, Malanga et al. (2003) indicated that the
pathologic changes in one structure may alter the
examination outcome of a different structure. Therefore,
prior to data collection, all subjects entering the study
underwent a structured and standardized clinical exam-
ination, in order to rule out any condition other than
PFPS (bursitis, tendonitis, damage to the articular
cartilage, tears of the menisci, ligaments or joint capsule,
patellar subluxation or dislocation, etc.). The clinical
examination comprised of history taking, review of the
medical records, inspection, and a set of standard
orthopaedic tests (patellar ballottement test, assessment
of both active and passive joint range of motion,
palpation of the knee joint—including the detection of
abnormal temperature, varus/valgus stress tests, Lach-
man’s test, anterior and posterior drawer test, pivot shift
test, McMurray’s test for both the medial and the lateral
meniscus, Apley’s test, and muscle testing of the knee)
(Winkel and Aufdenkampe, 1994; Reider, 1999). The
patellar ballottement test was performed with the
patient lying supine and the knee extended. In this
position, the examiner pushed the patella posteriorly
with two fingers using a quick motion. In the case of a
large effusion, the patella descends to the patella and is
felt to strike it with a distinct impact (Reider, 1999).
Reviewing the medical records of the study participants,
it was noted that specialized diagnostic imaging
techniques were used in 34 of 45 patients. One imaging
technique (magnetic resonance imaging, computer
tomography, radiographs, radioisotope scan or ultra-
sound scanning) was used in 18 cases, while up to 5
different imaging techniques were used in the remaining
16 subjects.
All subjects were screened according to the in- and
exclusion criteria by the same investigator, in order to
determine study eligibility and group assignment (PFPS
group or control group). Next, the patients were asked
to fill in a set of self-reported measures: three visual
analogue scales (VAS for pain at rest, pain during
movement, and pain at night), and the Dutch version of
the Modified Functional Index Questionnaire (MFIQ-
DV). A detailed description of the MFIQ-DV is given in
the ‘Self-assessment tools’-section. Afterwards, a second
investigator, blinded to the group assignment, per-
formed a battery of patellofemoral tests in the following
order: the vastus medialis coordination test, patellar
apprehension test, Waldron’s test (phase 1 and 2),
Clarke’s test, and the eccentric step test.
3.2. Self-assessment tools
Visual analogue scales (VAS—100 mm) for pain at
rest, pain during movement, and pain at night, were
used. The pain scores obtained with the VAS are
believed to be reliable (Jensen et al., 1986; Harms-
Ringdahl et al., 1986) and sensitive to change (Jensen et
al., 1986). Using a time interval of 2 days in a sample of
24 PFPS patients, the test-retest reliability coefficients
(intraclass correlation coefficients) ranged between 0.77
and 0.79 (Bennell et al., 2002).
Selfe et al. (2001a) constructed the MFIQ. The
Cronbach Alpha coefficient for internal consistency
was 0.83 in a sample of 77 patients with PFPS (Selfe et
al. 2001a). Assessing the test-retest reliability of the
MFIQ total scores it was found that the 95% confidence
interval (CI) was 7 11.2 (SD75.47) (Selfe et al., 2001b).
A change of 10 points in the overall score on the MFIQ
was considered clinically sensitive (Selfe et al., 2001b). In
order to make the MFIQ an appropriate questionnaire
for the assessment of functionality in Dutch-language
PFPS patients, the first and the third author indepen-
dently translated the English version of the MFIQ into
Dutch. Afterwards, both translations were compared
and combined into one version (the Modified Func-
tional Index Questionnaire-Dutch Version or MFIQ-
DV1
). The MFIQ-DV contains ten closed-ended ques-
tions, using both three-point (the first two questions)
and four-point (questions three–ten) Likert scales. For
counting the total scores obtained with the MFIQ-DV,
the scoring system as described by Selfe et al. (2001a)
was used. This scoring system indicates that higher
scores are suggestive of more severe problems. In order
to exclude investigator bias, all study subjects were
asked to complete the questionnaire independently.
Patients with bilateral symptoms were asked to complete
the questionnaires for their most symptomatic leg only.
3.3. Clinical tests
3.3.1. Vastus medialis coordination test
The vastus medialis coordination test was performed
and interpreted as described by Souza (1997). The
patient lay supine, and the examiner placed his/her fist
under the subject’s knee and asked the patient to extend
the knee slowly without pressing down or lifting away
from the examiner’s fist (Fig. 1). The patients were
instructed to achieve full extension. The test was
considered positive when a lack of coordinated full
extension was evident, i.e. when the patient either had
difficulty smoothly accomplishing extension or recruited
ARTICLE IN PRESS
1
The MFIQ-DV can be obtained from the corresponding author.
J. Nijs et al. / Manual Therapy 11 (2006) 69–77 71

either the extensors or flexors of the hip to accomplish
extension. Souza (1997) suggested that a positive test
may be an indicator of dysfunction of the vastus
medialis obliquus muscle which may result in patellar
pain.
3.3.2. Patellar apprehension test
The patellar apprehension test, also referred to as the
Fairbanks apprehension test, was performed with the
patient lying supine and relaxed (Reider, 1999). The
examiner used one hand to push the patient’s patella as
lateral as possible, in order to obtain a lateral patellar
glide (Fig. 2). Starting with the knee flexed at 301, the
examiner grasped the leg at the ankle/heel with the other
hand and performed a slow, combined flexion in the
knee and hip (Reider, 1999; Malanga, et al., 2003). This
lateral glide was sustained throughout the test. The test
was considered positive when it reproduced the patient’s
pain or when apprehension was present. The apprehen-
sion can manifest itself in a number of ways, ranging
from verbal expressions of anxiety over grabbing the
knee to involuntary quadriceps muscle contractions (to
prevent further knee flexion) (Reider, 1999; Souza, 1997;
Malanga, et al., 2003).
3.3.3. Waldron’s test (phase I and II)
For phase I of Waldron’s test, with the patient lying
supine and the examiner pressed the patella against the
femur while simultaneously performing a passive knee
flexion with the other hand (Reider, 1999). Crepitus and
pain during a particular part of the range of motion are
considered signs of patellofemoral pain disorders
(Souza, 1997; Martens et al., 1995). For phase II, the
standing patient was asked to perform a slow, full squat,
again with the examiner performing a gentle compres-
sion of the patella against the femur. As was the case in
Waldron’s test phase I, pain and crepitus were of
interest for interpreting the test.
3.3.4. Clarke’s test (or patellofemoral grinding test)
Clarke’s test was performed with the patient lying
supine with both knees supported by a knee pad, in
order to create a sufficient amount of knee flexion and
consequent articulation of the patella in the patellofe-
moral joint. Performing the test in full extension might
even cause false-positive findings, due to pinching of the
suprapatellar pouch (Souza, 1997). While the patient
was relaxed, the examiner pressed the patella distally
(with the hand on the superior border of the patella) and
then asked the patient to contract the quadriceps muscle
(Souza, 1997; Malanga et al., 2003). If the patient’s pain
was reproduced during test performance, then the test
was considered positive. A positive Clarke’s test has
been suggested to be indicative for patellofemoral
disorders (Souza, 1997; Malanga et al., 2003).
3.3.5. Eccentric step test
For the eccentric step test, the patients wore shorts
and performed the testing in bare feet (Fig. 3). The step
was made of a stool 15 cm high. Selfe et al. (2001a), in an
attempt to standardize the height of the step against the
anthropometric differences between study participants,
adjusted the step height to 50% of the length of the
tibia. Selfe et al., (2001a) found that the eccentric step
test produced knee pain in 57 of 77 PFPS patients
(74%). The step was manufactured by wood, and a layer
of non-slip rubber was placed on top of the wood to
prevent slipping of the subjects while performing the
test. Selfe et al. (2001ab) used video equipment to
quantify the eccentric step test. Due to the time
consuming and expensive nature of this procedure, the
video equipment was deemed inappropriate for clinical
purposes and consequently not used in the present
investigation. Apart from the step height and the video
analysis, the eccentric step test was performed as
described by Selfe et al. (2001a). Briefly, each study
ARTICLE IN PRESS
Fig. 1. Vastus medialis coordination test.
Fig. 2. Patellar apprehension test.

participant was given a standard demonstration of the
test followed by standardized verbal instructions: ‘stand
on the step, put your hands on your hips, and step down
from the step as slowly and as smoothly as you can’.
Patients were asked to keep their hands on their hips
throughout the test performance. After each patient
performed the test with one leg, the procedure was
repeated using the other leg. A warm-up or practice
attempt was not allowed. The eccentric step test was
considered positive when the patients reported knee pain
during the test performance.
3.4. Statistics
All data were analysed using SPSS 11.0 r
for
Windows (SPSS Inc. Headquarters, 233 s. Wacker
Drive, 11th floor, Chicago, Illinois 60606, USA). The
following descriptive statistics were obtained: mean and
standard deviation (SD) for age and knee pain duration,
frequencies and percentages for gender distribution and
the number of left knees affected, and median and
interquartile range for the total scores obtained with the
MFIQ-DV. To examine the differences between the
PFPS and the non-PFPS group, both the Fisher exact
test (for gender distribution) and the Mann–Whitney U
test (knee pain duration, age, and the visual analogue
scales) were used.
The disease specificity of the MFIQ-DV scores was
assessed by examining the differences in both the total
and the item scores between the PFPS and the non-
PFPS groups (Mann–Whitney U test). Cronbach’s
alpha reliability coefficients were calculated as a
measure for estimating the internal consistency of the
item scores of the MFIQ-DV. Spearman Rank correla-
tion coefficients were calculated for the convergent
validity analysis (the total scores obtained with the
MFIQ-DV versus the visual analogue scales). The level
of significance was set at 0.05.
To examine the diagnostic value of the patellofemoral
tests, the positive and negative likelihood ratios were
calculated and interpreted as described by Fritz and
Wainner (2001). Likelihood ratios are considered the
best statistics for summarizing the usefulness of a
diagnostic test; sensitivity and specificity work in the
opposite direction of clinical decision making, while
predictive values are highly dependent on the pre-
valence of the condition of interest in the sample
(Fritz and Wainner, 2001). Since likelihood ratios are
ratios of probabilities, they can be treated as risk ratios
for the purposes of calculating CI (Deeks and Altman,
2004). The 95% CI for the likelihood ratios were
calculated as described by Kirkwood and Sterne (2003,
p. 155–156).
4. Results
Of the 45 knee patients enrolled, one had undergone
knee surgery and was therefore excluded. Five addi-
tional patients (seven knees) were classified as co-morbid
PFPS patients and were consequently excluded. Of the
remaining 39 study participants (59 symptomatic knees),
20 patients were classified in the PFPS group (31 knees),
and the remaining 19 in the control group (non-PFPS
sample—28 knees). The control group comprised of four
patients with a grade II injury of the medial collateral
ligament (one of which had a comorbid shin splints or
periostitis), one patient with a iliotibial band friction
syndrome, one with osteoarthritis of the knee, two with
an injury of the anterior cruciate ligament, three with a
meniscus tear (two of the medial meniscus and one of
the lateral meniscus), one with a stress fracture, one with
severe knee instability, one with severe overloading of
the muscles of the lower extremities, two with tendonitis
of the Quadriceps tendon, one with a contusion of the
knee, one with an injury of the M. Popliteus, and one
with both an injured joint capsule and several injured
knee ligaments. The demographic features of both the
PFPS and the non-PFPS group are presented in Table 1.
No statistically significant differences in age (Man-
n–Whitney U ¼ 185; 5; p ¼ 0:899), knee pain duration
(U ¼ 121; p ¼ 0:052), or gender distribution (p ¼ 0:320)
were found between the two groups.
ARTICLE IN PRESS
Fig. 3. Eccentric step test.

Regarding the self-reported measures, both the
descriptive statistics and the comparisons between the
PFPS and the non-PFPS group are presented in Table 2.
No statistically significant differences in pain intensity at
night (VAS night: Mann–Whitney U ¼ 175; p ¼ 0:595),
at rest (VAS rest: U ¼ 154; p ¼ 0:271), or during
movement (VAS movement: U ¼ 178:5; p ¼ 0:746) were
found between the PFPS and the non-PFPS group.
Regarding the disease specificity for the scores obtained
with the MFIQ-DV, neither the total scores (Man-
n–Whitney U ¼ 159; p ¼ 0:382), nor any of the indivi-
dual item scores (data not shown) showed a statistically
significant difference between the two groups. The
Cronbach Alpha coefficient was 0.71 for the PFPS
patients and 0.80 for the non-PFPS subjects. Further-
more, the convergent validity analysis revealed statisti-
cally significant associations between the total scores
obtained with the MFIQ-DV and the visual analogue
scales for pain during movement in both the PFPS
patients (rho ¼ 0:41; p ¼ 0:020) and the non-PFPS
subjects (rho ¼ 0:50; p ¼ 0:007). In the latter group,
there was a statistically significant correlation between
the pain intensity at rest and the MFIQ-DV overall
scores (rho ¼ 0:422; p ¼ 0:025). All Spearman Rank
correlation coefficients and corresponding p-values are
displayed in Table 3.
The outcome of the clinical tests for both groups is
presented in Table 4. The positive likelihood ratio was
2.26 for both the vastus medialis coordination test and
the patellar apprehension test. For the eccentric step
test, the positive likelihood ratio was 2.34. For the
remaining tests, the positive likelihood ratios were below
the threshold value of 2 (Table 5). For all five tests, the
negative likelihood ratios were above the threshold
value of 0.5.
5. Discussion
This study provided new insight into the scientific
value of five clinical tests for the diagnosis of PFPS in
knee pain patients. It was shown that the positive
likelihood ratio was 2.26 for both the vastus medialis
coordination test and the patellar apprehension test, and
2.34 for the eccentric step test. A likelihood ratio of 1
indicates that the test result does nothing to change the
odds favouring the condition of interest. A positive
likelihood ratio indicates a shift in odds favouring the
condition of interest (i.e. PFPS) when the test is positive.
A larger positive likelihood ratio is therefore desirable.
A positive likelihood ratio within the range of 2–5, as is
the case for the vastus medialis coordination test, the
patellar apprehension test, and the eccentric step test, is
considered to generate small, but sometimes important,
shifts in probability (Jaeschke et al., 1994). Thus, a
positive outcome on either the vastus medialis coordina-
tion test, the patellar apprehension test, or the eccentric
step test in a knee pain patient increases the probability
of PFPS to a small, but sometimes important degree.
Still, the intraobserver and the interobserver reliability
of these tests remain to be established. Given the
subjective interpretation of the vastus medialis coordi-
nation test, the examination of the intraobserver and
interobserver reliability of this test is highly recom-
mended. For the remaining tests, the positive likelihood
ratios were below the threshold value of 2, indicating
that given a positive test result, the probability that the
knee pain patient has PFPS is altered to a small, and
rarely important degree. Negative likelihood ratios
indicate a change in odds favouring the condition given
a negative test result. Consequently, a small negative
likelihood ratio will identify the test that is useful for
ruling out PFPS when negative (Fritz and Wainner,
2001). The negative likelihood ratios for all tests
exceeded the threshold value of 0.5 (Jaeschke et al.
1994), suggestive of clinically irrelevant information.
Indeed, negative likelihood ratios within the range of
ARTICLE IN PRESS
Table 1
Demographic features of both the PFPS (n ¼ 20) and the non-PFPS
group (n ¼ 19)
age (years
7SDa
)
number of
females
(%)
knee pain
duration
(months7
SD)
number of
left knees
affected
(%)
PFPS 31.0715.2 9 (45.0) 45.1755.2 17 (54.8)
Non-PFPS 26.578.5 5 (26.3) 35.1758.9 14 (50.0)
a
standard deviation.
Table 2
Descriptive statistics of the self-reported measures taken from 20 PFPS and 19 non-PFPS patients
VASa
rest Mean7SDb
;
[range]
VASa
movement
Mean7SD; [range]
VASa
night Mean7SD;
[range]
MFIQ-DV Median; IQRc
[range]
PFPS 20.5728.2 [0.0;83.0] 51.2723.9 [8.0;98.0] 8.6720.5 [0.0;77.0] 32.5; 23.8 [15;65]
Non-PFPS 18.4727.9 [0.0;87.0] 51.2732.5 [0.0;100.0] 12.6724.5 [0.0;94.0] 35.0; 11.3 [5;55]
a
visual analogue scale for pain at rest, during movement, and at night,
b
standard deviation,
c
interquartile range.

0.5–1 alter the probability to a small, and rarely
important degree (Jaeschke et al., 1994).
Selfe et al. (2001a) reported that the eccentric step test
produced knee pain in 57 of 77 PFPS patients (74%). In
the present study, we were unable to confirm these
results: the eccentric step test provoked pain in 13 of 31
PFPS knees (41%). The eccentric step test was
performed in the same way as described by Selfe et al.
(2001a), subject to a different step height (15 cm in our
study versus an adjusted step height to 50% of the
length of the tibia in the Selfe et al. trial). The mean step
height used in the Selfe et al. (2001a) was not reported.
In another study by Selfe (2000) using identical
methodology to adjust the height of the step, a modal
step height of 22 cm (range 20–26) was reported. Despite
the fact that the latter study addressed healthy subjects,
it can be assumed that the step height used in the Selfe et
al. (2001a) study on PFPS subjects was higher compared
to our fixed step height. This might explain the
discrepancy between the present data and those reported
by Selfe et al. (2001a), and suggests a relationship
between step height and painful responses.
The patellar apprehension test is performed primarily
to test the knee for patellar dislocation (Malanga et al.
2003; Reider, 1999; Souza, 1997) and not for diagnosing
PFPS. It should be noted, therefore, that the high
amount of patients presenting with a positive patellar
apprehension test, as seen in our sample, was not due to
the classical apprehension sign but due to pain
provocation during test performance. One study re-
ported a sensitivity of 39% of the patellar apprehension
test for the diagnosis of patellar dislocation (Sallay et
al., 1996). From their literature review, Malange et al.
(2003) concluded that no studies document the validity
of Clarke’s test for the diagnosis of PFPS. In addition,
we are unaware of data documenting the validity of the
vastus medialis coordination test, Waldron’s test, and
the patellar apprehension test for the diagnosis of PFPS
in knee pain patients. Consequently, we claim these data
to be the first documenting the validity of these clinical
tests for the diagnosis of PFPS in knee pain patients.
This study provided preliminary evidence supporting
the internal consistency and validity of the Dutch
version of the MFIQ, a self-assessment tool for
evaluating functionality in PFPS patients. The Cron-
bach Alpha coefficient was 0.71 for the PFPS patients
and 0.80 for the non-PFPS subjects. For interpreting
Cronbach’s Alpha coefficient, 0.80 is considered the
threshold value for sufficient internal consistency of the
different items included in the questionnaire (Dijkers
et al. 2002). Since shorter questionnaires are known to
be less reliable (Selfe et al. 2001b), we claim that even the
value of 0.71 supports the internal consistency of the
Dutch MFIQ. The convergent validity analysis revealed
statistically significant associations between the total
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Table 3
Convergent validity of the MFIQ-DV in PFPS (n ¼ 20) and non-PFPS
(n ¼ 19) patients: correlation analyses between the MFIQ-DV total
scores and visual analogue scales
PFPS Patient non-PFPS Patient
MFIQ-DV rhob
(p-value) MFIQ-DV rho (p-value)
VASa
rest À0.21 (0.208) 0.42 (0.025)
VASa
movement 0.42 (0.020) 0.50 (0.007)
VASa
night À0.08 (0.671) 0.36 (0.060)
a
visual analogue scale for pain at rest, during movement, and at
night,
b
Spearman Rank correlation coefficient.
Table 4
Outcome on the clinical tests in the PFPS (n ¼ 20; 31 symptomatic
knees) and non-PFPS patients (n ¼ 19; 28 knees)
Test PFPS Non-PFPS
Vastus medialis coordination test positive 5 (16.1%) 2 (7.1%)
Patellar apprehension test positive 10 (32.3%) 4 (14.3%)
Waldron’s test phase I positive 14 (45.2%) 9 (32.1%)
Waldron’s test phase II positive 7 (22.6%) 6 (21.4%)
Clarke’s test positive 15 (48.4%) 7 (25.0%)
Eccentric step test positive 13 (41.9%) 5 (17.9%)
Table 5
Validity of five clinical tests for the diagnosis of PFPS in knee patients.
Test +LRa
95%CIb
ÀLRc
95%CI
Vastus medialis coordination test 2.26 1.88 to 2.92 0.90 0.57 to 0.88
Patellar apprehension test 2.26 2.09 to 2.45 0.79 0.83 to 0.98
Waldron’s test phase I 1.41 0.62 to 3.20 0.81 0.36 to 1.84
Waldron’s test phase II 1.05 0.98 to 1.13 0.99 0.92 to 1.06
Clarke’s test 1.94 1.05 to 3.59 0.69 0.37 to 1.28
Eccentric step test 2.34 1.88 to 2.92 0.71 0.57 to 0.88
a
Postive likelihood ratio,
b
95% CI,
c
Negative likelihood ratio.

scores obtained with the MFIQ-DV and the visual
analogue scales for pain during movement in both the
PFPS patients and the non-PFPS subjects. These results
support the convergent validity of the total scores
obtained with the MFIQ-DV in both PFPS and non-
PFPS knee patients. Neither the total scores obtained
with the MFIQ-DV, nor any of the individual item
scores indicated a statistically significant difference
between the PFPS and the non-PFPS knee pain patients.
Thus, the disease specificity of the MFIQ-DV for PFPS
patients is questionable. It is concluded that these data
support the internal consistency and the convergent
validity of the scores obtained with the MFIQ-DV in
both PFPS and non-PFPS patients. Before the use of the
MFIQ-DV in clinical practice and research settings can
be advised, however, the test-retest reliability, content
validity, responsiveness, and other forms of validity
should be examined.
These results should be interpreted with some caution.
First, some of the tests of interest in the present
investigation are manual tests during which the tester
applies a force to the patella. It is difficult to quantify
and to standardize the amount of force used, this issue
requires further investigation. Second, this sample was
not randomly selected. Still, most reports on PFPS
studied a sample of convenience (e.g. Bennell et al.,
2002, Watson et al., 2001; Brechter and Powers, 2002;
Thome´ e et al., 2002). A high number of rehabilitation
centres and private practices for physiotherapy were
contacted for the subjects’ recruitment. Since PFPS
patients were the topic of interest in the present study,
physiotherapists might have primarily referred patients
with suspected PFPS for study participation. This might
have introduced selection bias into the trial, as
evidenced by the high number of PFPS patients in this
sample of knee pain patients (20 of 39% or 51%), which
is distinctive from previously reported epidemiological
data suggesting that between 25% and 40% of knee
patients have PFPS (Brody and Thein, 1998; Powers,
1998; Wilk et al., 1998). Still, since likelihood ratios are
independent of the prevalence of the condition of
interest in the sample (Fritz and Wainner, 2001), this
is unlikely to have biased these results. Third, the testers
were senior physical therapy students. At the time the
study took place, they were holders of a bachelor degree
in physical therapy and completed their final year of the
master program in physical therapy. These students
received a significant amount of training prior to the
study. Still, their skills may not be reflective of most
experienced physical therapists and medical doctors who
currently use these tests. On the other hand, from a
study examining the intertester reliability of clinical tests
of the sacroiliac joint it was concluded that the years of
experience did not affect the reliability (Potter and
Rothstein, 1985). Fourth, physical examination tests are
generally not performed in isolation, but together with
the interview, inspection and several other tests. Con-
sequently, the data presented here are somewhat
artificial. Finally, the order of the tests performed
should have been randomized. There may have been
cumulative increases in pain. To test for this cumulative
effect it would have been of interest to obtain a VAS
from each subject after each test was performed. Even
with the order of the tests randomized, this would
enable to identify bias related to cumulative increases in
pain.
6. Conclusion
These data question the validity of Waldron’s test
phase I, Waldron’s test phase II, and Clarke’s test in the
diagnosis of PFPS. In patients presenting with knee
pain, a positive outcome on either the vastus medialis
coordination test, the patellar apprehension test, or the
eccentric step test increases the probability of PFPS to a
small, but sometimes important degree. Furthermore,
the present report provided evidence supporting the
internal consistency, and the convergent validity of the
scores obtained with the MFIQ-DV in both PFPS and
non-PFPS knee pain patients. The disease specificity of
the MFIQ-DV for PFPS patients is questionable.
Acknowledgements
The authors would like to thank all the study
participants, and all the physicians and physiotherapists
who assisted with subject recruitment. Special thanks to
Katrien Vanherberghen, who holds a master degree in
physical therapy and has English as her native language,
for editing the final version of the manuscript. The
authors are grateful to Rene´ Nijs (PhD, statistician) for
his advice on the statistical analysis.
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