Knee Surg, Sports Traumatol, Arthroscopy
(1996) 4 : 22-26
9 Springer-Verlag 1996
P. P. Mariani
E. Adriani
G. M a r e s c a
C. G. M a z z o l a
Received: 8 December 1995
Accepted: 12 March
P. P. Mariani ( ~ ) 9G. Maresca
1~ Orthopaedic Clinic University
"La Sapienza", Piazzale Aldo Moro, 5,
1-00185 Rome, Italy
E. Adriani
Ospedale Sandro Petrini, USL Roma B,
Via dei Monti Tiburtini,
1-00157 Rome, Italy
C. G. Mazzola
Ospedale Civile di Lavagna,
Via Don Bobbio,
25 Lavagna (Genova), Italy
A prospective evaluation
of a test for lateral meniscus tears
Abstract A test for d i a g n o s i n g lesions to the lateral m e n i s c u s is described. D u e to our inability to find
its description in the literature w e
called it ' d y n a m i c test'. The accur a c y o f this test was assessed in
421 knees. The test was c o m p a r e d
against arthroscopic findings in all
cases. Inter-rater reliability was also
estimated a m o n g three observers,
who were shown to have a K coefficient ranging from 0.61 to 0.85. In a
series o f healthy subjects, the test
was positive in eight n o r m a l knees
(9.4%), but none o f these false-posi-
tives was u n a n i m o u s l y identified b y
m o r e than one rater. This m a n i p u l a tive test was v e r y accurate: sensitivity 85%, specificity 90.3%, positive
predictive value 73.2%, negative predictive value 95% p r e v a l e n c e 23.7%
and a c c u r a c y 89%. Thus, the test
seems to be a tool that can i m p r o v e
the diagnostic a c c u r a c y o f m e n i s c a l
lesions. A n i m p o r t a n t feature o f this
test is that it can be p e r f o r m e d in patients with acute injuries.
K e y w o r d s Lateral m e n i s c u s test 9
Diagnostic knee
Introduction
Materials and methods
The clinical diagnosis o f m e n i s c a l tears m a y be difficult
even for e x p e r i e n c e d surgeons to make. Several tests have
been d e s c r i b e d for the diagnosis o f m e n i s c a l disorders,
and their accuracy and reliability have been assessed b y
m a n y authors [1, 3 - 7 , 8, 11, 12] with v a r y i n g results. The
m o s t c o m m o n test, the M c M u r r a y test, is reported to have
a sensitivity ranging from 16% [7] to 62% [11] and a
specificity from 41.7% [11] to 98% [7]. M o s t o f the diagnostic errors in these studies were associated with the lateral meniscus.
F o r several years we have d i a g n o s e d lesions to the lateral m e n i s c u s using a tool w e call the ' d y n a m i c test'. D u e
to our inability to find any description o f this m a n o e u v r e
in the literature we will go on calling it this w a y in this
study. The p u r p o s e o f this study was to d e t e r m i n e
p r o s p e c t i v e l y the sensitivity and specificity o f this test,
using arthroscopic findings as the gold standard. A prel i m i n a r y study was carried out to assess inter-rater reliability and the test's positivity in healthy controls.
We carried out two preliminary studies to assess the agreement between the examiners (interobserver reliability) and the frequency
of a positive dynamic test in healthy controls.
The first of the preliminary studies was carried out over a period of 3 months, during which three examiners (A: Ezio Adriani,
B: Gaetano Maresca, and C: Claudio Guido Mazzola) concurrently
but individually examined 54 patients scheduled for arthroscopic
surgery for various disorders. The data obtained from the examiners were used to estimate the interobserver reliability by the Kappa
coefficient [6, 13]. The Kappa coefficient is defined according to
the equation (Table 1):
K = observed proportion of agreement - expected proportion in agreement
1 - expected proportion in agreement
The observed proportion of agreement is defined as the sum of the
cases in which two raters are in agreement as to the positivity or
negativity of the test divided by the total number of cases (A + D
A + D
.
- m the example given in Table 1). The expected proportion
N
of agreement is based on the expected values calculated in
the same way as those used in a chi-square test.
23
T a b l e 1 Example of the data table for comparing two observers
using the K test (the expected values are shown in brackets; A and
D = no. of cases with agreement between two observers; B and
C = no. of cases without agreement between two observers)
Observer X
Positive
Observer Y
Positive
Negative
Total
A
B
E
[E*G/N]
[E* H/N]
(A +B )
C
D
F
[F*G /N]
[F* H/N]
( C +D )
G
H
(A+C)
(B+D)
N
Total cases
Negative
Total
of the visit. In this manner, we examined 85 'normal' knees; 15
knees were excluded from the series because a previous trauma
was identified upon examination.
After this screening, we set up the protocol for selecting the patients to submit to examination and surgery. W e adopted the following exclusion criteria: (1) previous lateral meniscectomy; (2)
patients with synovial disease; (3) patients with acute capsuligamentous injury or chronic posterolateral instability. Using the criteria, we enrolled 405 consecutive patients awaiting elective
arthroscopic surgery. The examiner was blind to the patient's preoperative diagnosis. The data were archived in a database and subsequently used to evaluate the sensitivity, specificity, and the positive and negative predictive values, according to the following
formulas (Table 2).
( True positive + False negative )
Prevalence :
(A+C)
In Table 1 the expected values are shown in brackets. Thus,
substituting the formula we have:
N
N
100 • -
Sensitivity :
+
( Total cases )
N
N
True positive
No. meniscal tears
True positive
K=
(True positive + False negative )
(A)
100 • - -
(A+C)
The Kappa coefficient can be negative or positive; its value is 0
when agreement occurs only at the chance-expected level, and 1.0
when agreement is perfect. In our preliminary study the Kappa coefficient was evaluated by comparing all three observers.
The second preliminary study included the examination of 50
young subjects (normal controls; mean age 25 years, range 15-37
years) who came to our attention for a problem related to the upper
extremities, who had no previous history of surgery or trauma to
the knees, and who in any case had no knee symptoms at the time
T a b l e 2 The typical 2 x 2
contingency table
Specificity :
True negative
No. healthy meniscal
True negative
( True negative + False positive )
100 x -
(D)
-
Dynamic
test
Torn
meniscus
Healthy
meniscus
Positive
A
True positives
85
B
False positives
31
C
False negatives
15
D
True negatives
290
A+C
B+D
No. meniscal tears
100
No. healthy menisci
321
No. negatives
305
N
Total cases
421
[100 x (D)/(B + D)]
Specificity
90.3%
[100 x (A)/(A+B)]
PVP
73.2%
[100 x (D)/(C + D)]
PVN
95%
Negative
[100 x (A)/(A+C)]
Sensitivity
85%
[100 x (A + D)/N]
Accuracy
89%
A+B
No. positives
116
C+D
24
Positive predictive value :
True positive
[ No. positive ]
True positive
( True positive + False positive )
PVP
Negative predictive value :
(a)
100 x - -
(A+B)
True negative
[ No. negative ]
True negative
45 ~, the knee bent about 90 ~, and the lateral border of the foot resting on the examination bed. In this position the femur is rotated externally, whereas the tibia is rotated internally (Fig. 1). The knee is
in a varus position due to the effects of gravity. As examiner's index finger palpates the lateral joint line, tenderness may be elicited
in this position, even though this is not pathognomonic for the test.
By keeping pressure on the outer rim, the examiner progressively
adducts the hip, while keeping the degree of flexion of the knee the
same. During the manoeuvre, the knee varus is reduced and at the
same time the femur is rotated internally. The meniscus is thus
squeezed between the femur and the tibia, and pushed outwardly
against the pressure of the examining finger.
The test is considered positive if (1) any pain that may be present due to the pressure of the finger increases during the manouvre or (2) a sharp pain is felt when the final position is reached.
(True negative + False negative)
PVN
Accuracy:
(D)
Results
100 x - -
(C+D)
No. true
Total cases
( True negative + True positive )
Total cases
(A+D)
100 x - -
(N)
In all, 405 consecutive patients underwent arthroscopic examination by the senior author who was blinded to the test results. Bilateral arthroscopy was performed in 16 patients, giving a total of 421
knees examined. The patients, 243 men and 162 women, ranged in
age from 14 to 77 years (mean 34 years). The right side was affected in 246 cases (58.43%).
T h e i n t e r o b s e r v e r r e l i a b i l i t y u s i n g the d y n a m i c test on 54
p a t i e n t is r e p o r t e d in T a b l e 3, w h i c h c o m p a r e s t h e c o n t i n g e n c y tables o f e x a m i n e r s A, B and C. T h e K c o e f f i c i e n t w a s c a l c u l a t e d f r o m the v a l u e s in the table; in s u m mary, it p r o v i d e d the f o l l o w i n g i n d i c a t i o n s :
C o m p a r i s o n b e t w e e n A and B (Table 3 a):
K = (A + D / N ) - [(E*G/N) + (F*H/N)/N] / 1 - [(E*G/N)
+ (F*H/N)/N]
K = (13 + 35/54) - [ ( 1 5 " 1 7 / 5 4 ) + ( 3 9 * 3 7 / 5 4 ) / 5 4 ] /
1 - [(15"17/54) + (39*37/54)/54]
K = 0.88 - ( 4 . 7 2 + 2 6 . 7 2 / 5 4 ) / 1 - ( 4 . 7 2 + 2 6 . 7 2 / 5 4 )
K = (0.88-0.58) / (1-0.58); K = 0.3/0.42
[ K = 0.71]
C o m p a r i s o n b e t w e e n A and C (Table 3 b):
The dynamic test
The patient is examined in the supine position, the leg positioned
with the hip abducted 60 ~, flexed and rotated externally by about
K = (A + D / N ) - / ( E ' G / N )
+ (F*H/N)/N]
+ ( F * H / N ) / N ] / 1 - [E*G/N)
K -- (14 + 37/54) - [ ( 1 5 " 1 6 / 5 4 ) + ( 3 9 * 3 6 / 5 4 ) / 5 4 ] /
1 - [(15"16/54) + (39*36/54)/54]
K = 0.94 - ( 4 . 4 4 + 2 7 . 4 4 / 5 4 ) / 1 - ( 4 . 4 4 + 2 7 . 4 4 / 5 4 )
l#
K = ( 0 . 9 4 - 0 . 5 9 ) / ( 1 - 0 . 5 9 ) ; K = 0.35/0.41
[K--0.S5]
C o m p a r i s o n b e t w e e n B and C (Table 3 c):
K = (A + D / N ) - [(E*G/N) + (F*H/N)/N] / 1 - [(E*G/N)
+ (F*H/N)/N]
K = (12 + 33/54) - [ ( 1 7 " 1 6 / 5 4 ) + ( 3 7 * 3 8 / 5 4 ] /
1 - [(17"16/54) + (37*38/54)/54]
K
=
0.83
-
(5.03+26.03/54) / 1 - (5.03+26.03/54)
K = (0.83-0.57) / (1-0.57); K = 0.26/0.43
[ K = 0.61]
Fig. 1 The dynamic test
T h e s e c o n d p r e l i m i n a r y study e x a m i n e d 85 h e a l t h y k n e e s ;
o n l y 8 k n e e s g a v e a p o s i t i v e test, but in no c a s e did all
t h r e e raters a g r e e that the test was p o s i t i v e . A test w a s
rated as p o s i t i v e b y e x a m i n e r s A and B in o n e c a s e and
e x a m i n e r s A a n d C in t w o cases; tests w e r e p o s i t i v e o n l y
for rater A in o n e case, o n l y for rater B in t w o cases and
o n l y for rater C in an a d d i t i o n a l t w o cases.
25
Table 3a Comparison between observers A and B with the K test
Observer B
Positive
Negative
Total
Positive
13
[4.72]
2
[10.28]
15
(A + B)
Negative
4
[12.28]
35
[26.72]
39
(C + D)
Total
17
(A + C)
37
(B + D)
54
Observer A
Table 3 b Comparison between observers A and C with the K test
Observer C
Positive
Negative
Total
Positive
14
[4.44]
1
[10.55]
15
(A + B)
Negative
2
[11.55]
37
[27.44]
39
(C + D)
Total
16
(A + C)
38
(B + D)
54
ObsetwerA
Table
3e
Comparison between observers B and C with the K test
Observer C
Positive
Negative
Total
Positive
12
[5.03]
5
[11.96]
17
(A + B)
Negative
4
[10.96]
33
[26.03]
37
(C + D)
Total
16
(A + C)
38
(B + D)
54
Observer B
In 421 subjects submitted to arthroscopy, a lateral
meniscal tear was found in 100 patients. Fifty-eight percent of these cases had associated an anterior cruciate ligament tear.
The type of lesions included longitudinal tears (24%),
radial tears (36%), horizontal tears (13%) and complex
(horizontal and/or longitudinal) tears (27%). In four patients a cyst of the lateral meniscus was present.
Examination of 421 knees compared in terms of the
arthroscopic findings gave the results shown in the 2 • 2
contingency table (Table 2). We had 85 true-positives and
31 false-positives, 290 true-negatives and 15 false-negatives.
Table 2 demonstrates the clinical accuracy of the dynamic test in a population about to undergo operation with
85% sensitivity and 90.3% specificity. The positive pre-
dictive value was 73.2%, and the negative predictive
value was 95%, with a prevalence of 23.7% and accuracy
of 89%.
Discussion
Occasionally, the patient's description of his (or her)
symptoms suffices to make a diagnosis of a meniscal lesion, but often only a very thorough evaluation of all
symptoms and tests allows us to solve the diagnostic
problem. As stated by Barry et al. [2], it is often the combination of symptoms and clinical signs that leads to the
correct diagnosis. A history of locking is of great diagnostic significance for a bucket-handle tear of the meniscus with displacement of the fragment. But this classical
presentation of locking is very rarely produced by the first
injury, and other causes, such as muscle contractures or
joint effusion, can produce the same limitation of motion.
A great number of special diagnostic signs have been
described for the diagnosis of a meniscal lesion. Most depend on the presence of a point of tenderness in the articular joint line and/or the presence of an audible 'snap' or
'click'. Flexion and extension of the knee with internal or
external rotation displaces the fragment of the meniscus
and can enhance these symptoms.
Tenderness localized at the joint line is one of the most
valuable diagnostic signs [1, 2, 9-11], but it is positive in
only 6 0 % - 8 0 % of cases [12]. The Apley test, one of the
best-known and reliable signs, is positive in only
4 0 % - 6 0 % of meniscal lesions [1, 2, 9-11]. Anderson and
Lipscomb [1] evaluated the sensitivity and specificity of
the McMurray test and found it positive in only 68% of
the cases. Most diagnostic errors were associated with lateral meniscus lesions [1, 4, 5, 7]. Evans et al. [7] have recently shown a 50% sensitivity of the McMurray test for
the lateral meniscus, with a very low positive predictive
value (29%).
Anatomical differences are one of the reasons behind
the greater difficulty in diagnosing lesions of the lateral
meniscus. In fact, as is widely known, the lateral meniscus, unlike the medial, has no firm tibial or femoral peripheral attachments and is relatively more mobile. The
menisci are displaced differently by knee motion, and the
lateral meniscus has a greater displacement than the medial. This observation accounts for its lower risk of tear.
When the different manipulative tests are performed,
knee motion displaces the menisci and produces abnormal
traction stresses on the capsule and synovium, accounting
for pain if there is a mobile fragment. Therefore, some diagnostic tests may be less accurate for lateral than medial
meniscus tears. For example, with the knee rotated internally, a thud on the lateral joint line elicited by the McMurray test is heard only seldomly and is not significant.
The only specific test for a lateral meniscus tear described in the literature is Cabot's sign [3, 11], a well-
26
k n o w n sign in European countries. Pain is elicited during
extension of the affected knee with the leg crossed over
the contralateral limb; while palpating the lateral joint line
with the thumb, the knee is extended against the resistance of the examiner's hand. In positive cases, pain or a
sensation of painful resistance is elicited from the patient.
The accuracy and reliability of Cabot's test have not
yet been rated or reported. A disadvantage of this test is
that it cannot be performed in acute cases due to the flexion in which the knee is held.
In the d y n a m i c test, the knee is always held at the
same degree of flexion, and the pain is elicited only by
means of varus stress and internal rotation of the femur.
During the manoeuvre, a compressive force is transmitted
through the lateral meniscus that is trapped between the
femur and the tibia with tension on its capsular attachment. Since the knee does not need to be flexed or extended, the test m a y also be performed in acute cases or in
the presence of a locked joint.
The results of our evaluation o f this test were highly
encouraging: sensitivity 85%, specificity 90.3%, positive
predictive value 73.2%, negative predictive value 95%,
prevalence 23.7% and accuracy 89%. Moreover, test reliability indicates a high level of agreement a m o n g the different examiners (K value ranging from 0.61-0.71 and
0.85).
Indeed, our diagnoses of lateral meniscus lesions are
better than those reported in the literature. One of the reasons m a y stern from the different exclusion criteria
adopted in this study. In fact, we excluded all cases with
recent capsuloligamentous injury or history of inflammatory synovial disease, conditions that m a y be a source of
spontaneous or elicited pain at the synovial meniscal attachment.
It is generally accepted that any meniscal test may be
considered pathognomonic for a specific tear, and all tests
have their diagnostic limitations. It is very important to
perform several of the multitude of tests that are available
before passing judgement as to a meniscal tear. The dynamic test, with its reliability; may b e c o m e an adjunct
diagnostic tool that used together with other well-known
tests m a y help improve our diagnostic accuracy for lateral
meniscus disorders.
References
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Clinical diagnosis of meniscal tears.
Description of a new manipulative test.
Am J Sports Med 14:291-293
2. Barry OCD, McManus F, McCauley P
(1983) Clinical assessment of suspected meniscal tears. Ir J Med Sci
152:149-151
3. Cabot JR (1954) Biomecanica de la
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(1994) McMurray's test tested. Knee
Surg Sports Traumatol Arthroscopy
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(1982) The diagnosis of meniscus
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sports medicine. Principles and practice, vol 1, chapter 5. Saunders,
Philadelphia
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test. Am J Sports Med 21 : 604-608
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2495-2497
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(1980) Meniscectomies in children.
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