British Journal of Rheumatology 1996;35(snppL 3):14—17
PROPOSED SCORING SYSTEM FOR ASSESSING SYNOVIAL
MEMBRANE ABNORMALITIES AT ARTHROSCOPY IN KNEE
OSTEOARTHRITIS
X. AYRAL,* A. MAYOUX-BENHAMOUf and M. DOUGADOS*
Departments of*Rheumatology and'f Rehabilitation, Hdpital Cochin, Universiti Rene Descartes, Paris, France
SUMMARY
The synovial membrane is thought to play an important role in both the clinical and the anatomical evolution of ostcoarthritia
Arthroscopy performed under local anaesthesia on an outpatient basis has been proposed as a means of cartilage and synovial
assessment for research purposes. The authors propose a scoring system for assessing anterior synovial abnormalities at
arthroscopy in knee osteoarthritis. This synovitis score takes into account the intensity and the extent of synovial lesions.
KEY WORDS: Arthroscopy, Knee osteoarthritis, Synovium, Synovitis score.
SYNOVIAL membrane is thought to play an
important role in both the clinical and the anatomical
evolution of osteoarthritis. It has been suggested that
the synovium, together with the subchondral bone,
muscles and ligaments, is involved in the occurrence of
pain in osteoarthritis [1]. The role of the synovium in
the degradation of articular cartilage has been shown
by the demonstration of active in vivo synthesis of
stromelysine and collagenase by cells of the human
rheumatoid synovium using both in situ hybridization
[2] and immunolocalization [3]. These studies suggested
that the osteOarthritic synovium also synthesizes
stromelysin, although at a lower level than does the
rheumatoid synovium. It is accepted that synovitis
occurring in osteoarthritis is related to the release of
fragments of cartilage proteoglycan molecules into the
joint fluid and/or to the presence of microcrystals in
synovial fluid or the synovial membrane [4].
Synovitis and cartilage lesions can be evaluated by
magnetic resonance and arthroscopy. Despite its
invasiveness, arthroscopy is still considered the 'Gold
Standard' for the assessment of articular cartilage and
synovium because it provides a direct and magnified
evaluation of these anatomical structures and permits
guided synovial biopsy in pathological areas. In the
knee joint, arthroscopy can be simplified by the use of
local anaesthesia, elimination of the tourniquet, use
of a small glass lens scope and performance on an
outpatient basis. This procedure has been proposed as a
means of cartilage [5] or synovial assessment [6] for
research purposes. Lindblad and Hedfors [6] found a
highly significant correlation between local macroscopic
signs of inflammatory activity assessed at arthroscopy
and microscopic signs in the corresponding tissue
specimen as revealed by routine histopathological and
immunohistochemical studies. Irrespective of clinical
diagnosis (chondromalacia or various types of
arthritis), a profound intra-articular variation in
inflammatory activity was seen at arthroscopy, with the
highest inflammatory activity always confined to the
area surrounding the cartilage and giving a patchy
distribution to synovitis [6].
Several authors have developed semi-quantitative
scales to assess arthroscopically synovial abnormalities
in chronic inflammatory joint diseases [7-10]. These
scales are limited, due to the lack of quantification of
the extent of synovitis within the joint As has been
previously proposed for articular cartilage lesions
[11-13], a scoring system for assessing synovitis at
arthroscopy of the knee should lead to a composite
index taking into account the intensity and the extent of
synovial abnormalities.
Three aspects of increasing intensity of synovial
abnormalities have been delineated by Watanabe et
al[l4] and proposed by Dorfmann [15] (see Fig. 1):
THE
(i) Normal synovium: few translucent and slender villi
formations with a fine vascular network clearly seen.
(ii) Reactive synovium: proliferation of opaque villi
formations. Their number is enhanced. The villi
show a normal morphology or appear somewhat
thicker and squat (aspect of 'cut grass')- The
vascular network cannot be seen due to a loss of
translucency.
(iii)Inflammatory synovium: isolated hypervascularization of the synovial membrane and/or proliferation
of hypertrophic and hyperaemic villi. This finding is
common in inflammatory joint diseases but may
occur in knee osteoarthritis.
As synovial abnormalities are inhomogeneously
distributed in knee osteoarthritis but predominate near
abnormal articular cartilage, the various areas of the
anterior synovium of the knee should be systematically
evaluated. The posterior synovium of the knee is
technically difficult to explore and is not routinely
examined.
The aim of this study was to establish a scoring
system for assessing anterior synovial abnormalities
(intensity and extent) at arthroscopy of the knee.
Correspondence to: Xavter Ayral, Clinique de Rhumatologje,
Hdpital Cochin, 27, rue du Faubourg Saint-Jaques, 75014 Paris,
France.
O 1996 British SocietyforRheumatology
14
AYRAL ETAL: ARTHROSCOPIC SYNOVTTIS SCORE
ILL!
15
quadriceps femoris muscle
posterior wall (suprapatellar pouch)
medial femoral gutter
cruciate ligaments
lateral femoral gutter
intercondylar notch
menisci
medial pcrimenboU synovlnm
lateral perlmeniscal synovium
medial femoral gutter
lateral femoral gutter
(atpad
antero-tateral wall
(suprapatellar pouch)
antero-medlal wall
(suprapatellar pouch)
patella
quadriceps femoris muscle
Fio. 1.—Diagram of the anterior synovial regions of the knee (right knee—joint opened).
TABLEI
Size of the different synovial regions of the knee
Suprapatellar pouch walls
Posterior
(1)
20%*
Femoral gutters
Antero-medial Antero-lateral
(2)
(3)
10%
10%
Fat pad
Perimeniscal areas
(4)
Medial
(5)
Lateral
(6)
Medial
(7)
Lateral
(8)
25%
10%
10%
5%
5%
Intercondylar
notch
(9)
5%
Total
100%
T h e size of the corresponding synovial region is expressed as a percentage of the whole anterior lynovium of the knee.
Synovitis score (0-»100) = 2OXJCI + 1 0 X X 2 + 1 0 X X 3 + 2 5 X J 4 + 1 0 X X J + 1 0 X X 6 + 5 X X 7 + 5 X J J + 5 X X9, xt being the synovitis intensity
(0,0.5 or 1.0) of the corresponding synovial region (see Methods).
METHODS
Definition of the scoring system required two steps.
The first was attribution of a point scaling system to
quantify the three aspects of synovial membrane. The
three synovial aspects were graded arbitrarily as follows:
normal, 0; reactive, 0.5; inflammatory, 1.0.
The second step consisted of determining the
anatomical size of each anterior synovial region of the
knee (see Fig. 1), which are (i) the suprapatellar pouch,
located above the upper part of the trochlea and divided
into (a) the posterior wall (located at the anterior part
of the femur) and (b) the antero-medial and
antero-lateral walls, which connect medially and
surround the patella; (ii) the medial and lateral gutters,
which are located medially and laterally between the
upper part of the trochlea and the perimeniscal
synovium; (iii) the medial and lateral perimeniscal
synovium; (iv) the fat pad located in front of the
trochlea; and (v) the synovium of the intercondylar
notch, covering the anterior cruciate ligament and the
infrapatellar plica.
To assess the size of these different synovial regions, a
cadaver knee was dissected and the anterior synovium
exposed. By computer assessment, the size of each
anterior synovial region was expressed as a percentage
of the whole anterior synovial surface.
RESULTS
The size of each anterior synovial region is
summarized and the mathematical formula of the
synovitis score is given in Table I. The investigator
evaluates the aspect of the synovium covering each
synovial region (normal, reactive or inflammatory). The
size of each synovial region is multiplied by the grade
(0, 0.5 or 1.0) of the synovitis intensity of this region.
The synovitis score of the knee joint is obtained by
adding the results of the various synovial regions {see
MRI IN THE ASSESSMENT OF RA
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TABLEH
Synovitis score—example of case record form
Suprapatellar pouch walls
Synovial region
Anatomic size (%)
Synovitis intensity
Normal
(grade 0)
Reactive
(grade 0.5)
Inflammatory
(grade 1.0)
Femoral gutters
Perimeniscal areas
Intercondylar
notch
Posterior
Anteromedial
Anterolateral
Fat pad
Medial
Lateral
20
10
10
25
10
10
5
5
5
20*
50
90
0
30
100
0
100
0
50
50
10
70
70
0
100
0
0
30
0
0
30
0
0
0
0
100
Medial
Lateral
Total
100
•Extent (%) of synovial membrane covered by the corresponding aspect of synovitij intensity in this example.
Synovitis score (see Results) = 20 x [(0 x 20) + (0.5 x 50) + (1 x 30)] /100 +10 x [(0 x 50) + (0.5 x 50) + (1 x 0)J/100 + 10 x [(0 x 90) + (0.5 x 10)
+ (1 x 0)]/100 + 25 x [(0 x 0) + (0.5 x 70) + (1 x 30)]/100 + 10 x [(0 x 30) + (0.5 x 70)+ (1 x0)]/100+ 10 x [(0 x 100) + (0.5 x 0) + (1 x0)]/100
+ 5 x [(0 x 0) + (0.5 x 100) + (1 x 0)] /100 + 5 x [(0 x 100) + (0.5 x 0) + (1 x 0)] /100 + 5 x [(0 x 0) + (0.5 x 0) + (1 x 100)] /100 = 20 x 0.55 + 10 x
0.25 + 10 x 0.05 + 25 x 0.65 + 10 x 0.35 + 5 x 0.5 + 5 x 1 =41.25
Table I), and ranges from 0 (normal synovium) to 100
(entire inflamed synovium).
In practice, one synovial region, especially the
posterior wall of the suprapatellar pouch, might include
three different aspects of synovium. The respective
extent of these different aspects, expressed as a
percentage of the whole size of this synovial region, is
reported on a case record form (see Table II) and taken
into account in the calculation of the synovitis score of
this particular synovial region. Table II shows an
example of the calculation of synovitis score in a
patient with an inhomogeneous distribution of synovial
abnormalities.
The calculation of the regional synovitis score of the
posterior wall of the suprapatellar pouch is obtained by
(i) multiplying the extent (expressed in percentage) of
the different aspects of synovium covering this posterior
wall by the respective grade of synovitis intensity of
these aspects of synovium (0, 0.5 or 1.0). The results
obtained for each aspect of synovium are added and the
sum is divided by 100 to obtain a mean synovitis
intensity (range 0-1) for this posterior wall (0.55 in this
example); then (ii) multiplying the anatomic size of the
posterior wall, i.e. 20, by its mean synovitis intensity
(0.55 in this example).
The calculation of the total synovitis score of the
knee is obtained by adding the results of the different
synovial regions. In this example, the value of the
synovitis score of the knee (range 0-100) is 41.25.
DISCUSSION
This proposed method of calculating a synovitis
score is the first quantitative system to take into account
the intensity of synovitis and its extent evaluated on the
basis of quantitative dissection of the different anterior
synovial regions of the knee. Further cross-sectional
and longitudinal studies should be carried out to
validate this scoring system, i.e. to assess inter- and
intraobserver reliability, and to define its validity and
sensivity to change. The use of arthroscopic scoring
systems for assessing synovial abnormalities and
chondropathy of the knee for research purposes should
lead to a better understanding of the interrelations
between synovitis and clinical phenomena on the one
hand, and between the status of synovitis and
chondropathy and disease evolution on the other.
This validation will permit the consideration of
arthroscopy as the 'Gold Standard' for the evaluation
of the severity of synovitis in osteoarthritis. Thereafter
it should be possible to compare this technique with
other, less invasive technics such as MRI.
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