Arthroscopy: The Journal of Arthroscopic and Related Surgery 7(2):162-170 Published by Raven Press, Ltd. 0 1991 Arthroscopy Association of North America
Arthroscopic
Evaluation of Synovitis in the Knee Joints
Masahiro Km-Osaka, M.D., *Osamu Ohno, M.D., and Kazushi Hirohata,
M.D.
Summary: It is not always easy to diagnose certain types of monoarthritis of the knee joints. In such cases, it is essential to evaluate the condition of the synovitis both macroscopically and microscopically, as the synovial appearance (synovitis) closely reflects the pathological condition (arthritis) of the knee joints. Arthroscopy is an excellent tool for visualizing and evaluating the condition of the synovium macroscopically. On arthroscopic examination, precise evaluation of the villi often provides clues, enabling accurate diagnosis. In addition, histological sections obtained from biopsy specimens in various cases of synovitis give significant information. In this article, arthroscopic observation and histological sections of various cases of synovitis are compared, and the diagnostic value and limitations of arthroscopic examination are discussed. Key Words: Synovitis-Arthritis-Diagnostics.
ovium, and pronounced villi formation is not generally observed. The normal synovium is translucent at the surface, and the vascular network with fine villi formation can be seen (1) (Fig. 1). Classification of the shape of the villi by Iino, one of the pioneers of arthroscopy, is shown in Fig. 2 (l-4). The villi usually observed in the normal synovium are feather-like, slender, rounded, or thinly membranous. Histologically, one to three layers of synoviocytes are loosely packed with an intercellular matrix in the surface and form the lining layer. The intercellular matrix consists of fine filamentous material and is sparsely distributed; therefore, the tine vascular network undeneath the lining layer can be easily observed (Fig. 3). Historically, in the knee joint the synovium is classified into three different types: fibrous synovium, areolar synovium, or adipose synovium. Fibrous synovium is characterized by few villi, a fine vascular network, and abundant fibrous connective tissue in the sublining layer. This type of synovium is often seen in the suprapatellar bursa. Areolar synovium is characterized by thin membranous villi and a loop-shape vascular network and is believed to reflect the synovial pathology precisely. This type is seen in the suprapatellar recesses. Adipose synovium is yellowish in color, is characterized by abundant adipose tissue, and is observed on the infrapatellar fat pad.
Embryologically, the joint space is understood as the space created in connective tissue. The synovium underlying this space is richly vascular without a basement membrane, and therefore chemical mediators in the blood may be transported easily into the synovial tissue and as a result synovitis may develop. Because the synovial appearance (synovitis) closely reflects the pathological condition (arthritis) of the knee joints, it is essential to evaluate the condition of the synovium both macroscopically and microscopically. Arthroscopy is the best way to visualize and evaluate the condition of the synovium macroscopically. In this article, we will compare the arthroscopic appearance and the histological sections of the various types of synovitis and discuss the diagnostic value and limitations of arthroscopic examination.
NORMAL SYNOVIUM Under arthroscopic examination, there is a minor variation in the shape of the surface of the synFrom the Department of Orthopaedic Surgery, Kobe University School of Medicine, Kobe, and *Department of Orthopaedic Surgery, Sanda Municipal Hospital, Sanda, Japan. Address correspondence and reprint requests to Dr. M. Kurosaka at Department of Orthopedic Surgery, Kobe University School of Medicine, 7-5-2 Kusunoki-cho, Chuo-ku, Kobe 650, Japan.
162
lA,B
FIG. 1. There is a minor variation in the shape of the surface of the normal synovium. The normal synovium is translucent at the surface; thus, the vascular network can be observed. A: Suprapatellar recess. B: Suprapatellar bursa. C: Meniscosynovial junction. D: Intercondylar space.
lC,D
T
!
I Slender
Rounded
Thin membranous
Thick membranous
Mass-like
I
Anterior
Side
I
x-n
view
L3 I
JLLL
view
%
View in cross section
00
$0 0:
0
0
l 0 I
I Other
Fringe-like
1
Polyp-like
1
Clubbed
1
Twig-like
forms
nJx FIG. 2. Schema for description
of some typical forms of the villi. Reproduced
@!W with permission from (I 1.
FIG. 3. One to three layers of lining cells are loosely pa eked with intercellular matrix in the lining layer. Note the tine tilamentous material facing joint space (arrows). JS, joint spat :e.
FIG. 4. Arthroscopic view of suprapatellar bursa shows thte dilatation and hyperemia of blood vessels caused by reactiv’ e synovitis (A). B: Vasospasms and ischemia after injection of 0.05 mg epinephrine into the joint cavity.
TABLE 1. Types of synovitis in arthritides Etiology of synovitis
Villi shape
Vascular pattern
Slender, thin membranous Thick membranous, polyp-like, fringe-like Thick membranous, polyp-like, club-shaped, edematous Exudative changes
Normal
Thick membrane, grayish in appearance
Minimal
Psoriatic synovitis
Mild villi formation
Normal
Reiters syndrome
Formation not pronounced
Prominent
Behcet’s syndrome
Thick membranous fringe-like
Synovitis of pustulosis palmaris et plantaris
Reddish, clubbed-shape, edematous
Trauma or osteoarthritis Osteoarthritis
Rheumatoid arthritis Active, chronic, inflammatory synovitis Suppurative synovitis
Tuberculous
synovitis
Clearly visible
Histologic features Minimal thickening of lining-infiltrate of lymphocytes and plasma cells Mild thickening of lining-infiltrate of inflammatory cells
Difficult to see, marked increase in vessels
Marked thickening of the lining; edema is prominent with proliferation of inflammatory cells with necrotic changes
Not observable, bleeding, debris
Lining cells do not proliferate; congestion and dilatation of the vessels-leukocytic infiltrate with edema Thickening of the lining with little vascular proliferation; prominent epithelial and Langhans’ giant cells around caseous necrosis No lining proliferation; lymphoid follicles common Lining cells proliferate with lymphocytes and plasma cells; no thickening of the fibrous connective tissue; marked increase in vascular network Proliferation of lining cells with infiltration of plasma cells and lymphocytes; minima1 vascular proliferation and thickening of fibrous connective tissue Moderate proliferation of lining cells and inflammatory infiltration; no thickening of the fibrous connective tissue
or
Not visible
FIG. 5. Top: Arthroscopic observation of medial synovial shelf shows proliferation of villi. Bottom: Histological examination of the synovial shelf revealed a focal infiltration of lymphocytes. This is one of the extreme cases of reactive synovitis caused by medial shelf syndrome.
FIG. 6. Top: Arthroscopic appearance of the synovium of osteoarthritis shows thin membranous villi and vascular network. Bottom: Nonspecific synovitis with mild infiltration of the inflammatory cells and proliferation of lining cells are observed histologically.
M. KUROSAKA
166
FIG. 7. Suppurative arthritis. Top: The synovium is markedly edematous, congested, and bleeds easily. Bottom: Histologically, suppurative coating consisting of fibrin and erythrocytes is observed. In the interstitial tissue, a number of polymorphonuclear cells infiltrate, and inflammatory edema exists.
Because the synovium is not a dense fibrous tissue, it becomes congested and edematous during prolonged arthroscopic examination; therefore, assessment should be done immediately (43. Also, the color of the normal synovium is much influenced by the intraarticular injection of small amounts of vasoconstrictors (Fig. 4). However, synovial color is not influenced by vasoconstrictors when inflammatory changes such as congestion and edema exist. It is sometimes useful to use vasoconstrictors to differentiate pathological synovitis from noninflammatory congestion of the vascular network. SYNOVIUM IN VARIOUS ARTHRITIDES Although pathological Arthroscopy,
there is significant variation in the condition of the synovium, in this ar-
Vol. 7, No. 2, 1991
ET AL.
FIG. 8. Top: Arthroscopic view of the synovium shows early stage of rheumatoid arthritis (RA). The congestion of blood vessels and slight edematous swelling of synovium are observed. Bottom: Histologically, nonspecific inflammatory change can be seen. It is difficult to make a definite diagnosis of RA at this stage.
title we will discuss the arthroscopic appearance of various types of synovitis in conjunction with their histological observation (Table 1). The types of synovitis to be discussed are reactive synovitis (traumatic synovitis and osteoarthritis), suppurative synovitis, tuberculous synovitis, rheumatoid synovitis, and synovitis caused by rheumatoid allied diseases.
REACTIVE SYNOVITIS In traumatic synovitis, except for the very acute phase immediately after the trauma, proliferation of the villi is the only finding observed during arthroscopy. However, the shape of the villi is not significantly different from that of the normal synovium, and arthroscopic observation does not provide us with specific information (Fig. 5). This is also true for the histological observation. Usually there is a
EVALUATION
OF SYNOVITIS
FIG. 9. Top: Arthroscopic appearance of the synovium shows opaque, hyperemic, and edematous swelling of villi and represents the exudative inflammatory change. Bottom: Marked infiltration of lymphocytes and plasma cells are found histologically.
minimal thickening of the lining layer and some infiltration of lymphocytes and plasma cells, which is characteristic of nonspecific synovitis. Occasionally, focal infiltration of lymphocytes is observed, but there are few cells and the vascular network in the lining layer is easily identified. In the synovium of osteoarthritis, the degree of villi formation is greater than that of traumatic synovitis and the shape of the villi can vary. A thick membranous shape, a fringe-like shape, or a polyplike shape occur, but usually the villi are not edematous (Fig. 6). The histological appearance is also characterized as nonspecific synovitis with mild proliferation and thickening of the lining layer and a mild infiltration of the inflammatory cells.
IN KNEE
FIG. 10. Top: Arthroscopic view of the synovium shows the granulation stage of rheumatoid arthritis. The villi of this type have a mixture of grayish and purple-red color, indicating the patchy distribution of the granulation tissue in the synovium. Note the form of villi, which is not edematous. Bottom Histological examination reveals infiltration of lymphocytes and plasma cells accompanied by proliferation of fibrous connective tissues.
ily. Also, a suppurative exudate is attached to the surface of the synovium, and the joint space itself becomes smaller. Therefore, arthroscopic observation is not always easy because the synovium is not translucent in suppurative arthritis and the vascular network cannot be examined (Fig. 7). Histologically, congestion and dilatation of the vessels are found in the lining and sublining layer. In the interstitial tissue, polymorphonuclear leukocytic infiltrate and inflammatory edema exist. However, the synoviocytes in the lining layer do not usually proliferate. RHEUMATOID
SUPPURATIVE
167
ARTHRITIS
(RA)
ARTHRITIS
In this type of synovitis, the synovium becomes markedly edematous. is congested, and bleeds eas-
The histological appearance of the synovium in RA varies widely with exudation, inflammatory cell infiltration, and granulation depending on the stage Arthroscopy,
Vol. 7. No. 2, 1991
M. KUROSAKA ET AL.
168
FIG. 11. Tuberculous synovitis. Top: Under arthroscopic examination, there are necrotic shreds and white granulation-like tissue. Bottom: Histological specimen shows the granulomatous change with proliferation of epithelioid cells.
of the disease. In the earliest stage of RA, a reddish color change of the synovium caused by congestion is the only finding seen on arthroscopic examination (Fig. 8). Infiltration of the inflammatory cells is less, and mild proliferation of the capillary vessels in the lining layer is the only finding even in the histological examination. It is difficult to make a definite diagnosis of RA at this stage because the abovementioned characteristics are often diagnosed as nonspecific monoarthritis. Once the disease advances, certain specific findings are present. The villi are fringe-like, polyp-like, clubbed, or twig-like and are prominent and often edematous (1). Edematous changes of the synovium commonly represent the exudative stage. Because of this exudative change, the surface of the synovium is covered by fibrin deposits (Fig. 9). In addition, marked proliferation of inflammatory cells and necrotic changes (4) in the synovium make the observation of the vascular network difficult. When the disease advances further, villi without Arthroscopy,
Vol. 7, No. 2, 1991
FIG. 12. Top: Arthroscopic appearance of psoriatic synovitis is similar to that of the early stage of reheumatoid arthritis with slight edematous swelling and hyperemia of synovium. Bottom: Histologically, proliferation of the lining cells is less. Note that the lymphoid follicle that is often encountered in psoriatic synovitis.
edema representing the formation of granulation can be seen. Villi of this type shown in Fig. 10 are a mixed grayish and purple-red color. Infiltration of lymphocytes and plasma cells and proliferation of fibrous connective tissue are found in the histological specimen of these villi.
TUBERCULOUS
SYNOVITIS
Tuberculous synovitis is the typical form of granulomatous inflammation. Histologically, this is the focal proliferative change characterized by rapid growth of the epithelioid cells and Langhans’ giant cells around the caseous necrosis. Although the histological appearance is uniformly characteristic, arthroscopic appearance of this type of synovitis is not necessarily uniform. In the very early stage, it is common that only minimal changes can be found in
EVALUATION
OF SYNOVITIS
FIG. 13. Reiter’s syndrome. Top: Arthroscopic appearance of the synovium shows hyperemia and bleeding of the vascular network. Bottom: Histologically, proliferation of the lining cells, and increased vascular network and infiltration of lymphocytes and plasma cells, are seen.
the synovium. However, once the disease advances, the lining layer of the synovium thickens with little vascular proliferation. At arthroscopy the synovium looks grayish and anemic (1) (Fig. 11). In addition, various findings such as marked fibrin deposition, deposition of material secreted from caseous degeneration, or a nonspecific mild form of synovitis may be seen. Therefore, at the time of arthroscopic examination it is crucial to make a thorough observation and take biopsy specimens from the different parts of the synovium (1) to avoid misdiagnosis.
OTHER TYPES OF SYNOVITIS Psoriatic synovitis When arthritis precedes dermatitis, diagnosis is often very difficult. There are no specific arthroscopic findings with this synovitis. Usually, psori-
IN KNEE
169
FIG. 14. Behcet’s syndrome. The shape of the vihi is thick membranous or fringe-like. Top: The arthroscopic findings are similar to that of the granulation stage of rheumatoid arthritis. Bottom: Histologically, proliferation of the lining cells and infiltration of lymphocytes and plasma cells are evident.
atic synovitis is very similar to reactive synovitis, with very mild villi formation and a normal vascular network (Fig. 12). Histologically, there is no proliferation of the synoviocytes in the lining layer and no infiltration of macrophages. However, formation of the lymphoid follicle is often encountered. Synovitis of Reiter’s syndrome In the early stage of this synovitis, the arthroscopic findings are similar to those found in suppurative arthritis. However, with progression of the disease, this synovitis closely resembles rheumatoid synovitis. Figure 13 shows the increased vascular network, congestion, and bleeding observed in the early phase. Here, the synovium becomes thickened with edema, bleeds easily, and villi formation is not pronounced. Histologically, marked inflammatory findings are seen with proliferation of the synoviocytes, an increased vascular network, and infiltration of lymphocytes and plasma cells. It is characteristic that thickening of fibrous connecArthroscopy.
Vol. 7, No. 2, 1991
170
M.KUROSAKAETAL. not usually seen. In the arthroscopic examination the villi are reddish, clubbed, and edematous. Occasionally, spotty bleeding is found on the surface and the vascular network is not visible (Fig. 15). Histologically, nonspecific inflammatory changes such as moderate proliferation of synoviocytes and infiltration of inflammatory cells may be seen. Usually there is no thickening of the fibrous connective tissue (Fig. 14). CONCLUSIONS
FIG. 15. Pustulosis palmaris et plantaris. Top: Under arthroscopic examination the villi are reddish, clubbed, and edematous. Note the capillary bleeding. Bottom: Histologically, nonspecific inflammatory changes can be seen.
tive tissue is not seen in the deep layer of the synovium. Synovltis of Behcet’s syndrome In this syndrome, approximately one-half of the patients have an episode of arthritis. On arthroscopic observation the synovium resembles that of the granulation stage of RA. The villi are usually thick membranous or fringe-like. Because no edematous change or vascular network is seen, the surface of the synovium is somewhat grayish (Fig. 14). Histologically, there are a proliferation of synoviocytes, infiltration of lymphocytes and plasma cells, and thickening of fibrous connective tissue. Synovitis of pustulosis palmaris et plantaris The synovitis of this disease characteristically shows exacerbation with significant effusion and remission. Nevertheless, destruction of the joint is Arthroscopy, Vol. 7, NO. 2, 1991
On arthroscopic examination, it is essential to evaluate the shape of the villi, the color of the synovium, the vascular network, and the edematous changes. It is crucial to decide whether the villi are edematous or not. If the villi are not edematous and are slender or thin membranous in shape, reactive synovitis caused by trauma or osteoarthritis is most likely. Thick membranous, polyp-like, or conus-like villi without edema suggest a proliferative process. When villi of this proliferative type show a clearly visible vascular network, synovitis caused by osteoarthritis in which cellular infiltration is minimal should be considered. On the other hand, when the vascular network is not observed in villi of the proliferative type, active, chronic, inflammatory synovitis such as RA should be suspected. When the villi are edematous with exudative changes and with a marked cellular infiltration, the vascular network cannot be observed in most cases. The edematous synovium with bleeding, exudation, and debris typically represents suppurative synovitis. In conclusion, arthroscopic examination of various types of synovitis gives significant information. When the diagnosis of monoarthritis is not certain, arthroscopic examination and synovial biopsy should be considered. On arthroscopic examination, precise evaluation of the villi often provides a clue to the diagnosis. REFERENCES 1. Watanabe M, Takeda S, Ikeuchi H. Atlas of arthroscopy, 2nd ed. Tokyo: Igaku Shoin, 1969. 2. Iino S. Normal arthroscopic findings of the knee joints in adults. J Jpn Orthop Assoc 1939;14:467-518. 3. Ikeuchi H. Normal arthroscopic findings of the knee joints. Instructional course lecture-I. Arthroscopy 1977;2:5744. 4. Ikeuchi H. In aid of understanding arthroscopic findings. Arthroscopy
1982;7:93-5.
5. Watanabe M. Arthroscopic findings of various pathological conditions in knee joints. Instructional course lecture-II. Arthroscopy
1977;2:65-73.
Arthroscopic
Evaluation of Synovitis in the Knee Joints
Masahiro Km-Osaka, M.D., *Osamu Ohno, M.D., and Kazushi Hirohata,
M.D.
Summary: It is not always easy to diagnose certain types of monoarthritis of the knee joints. In such cases, it is essential to evaluate the condition of the synovitis both macroscopically and microscopically, as the synovial appearance (synovitis) closely reflects the pathological condition (arthritis) of the knee joints. Arthroscopy is an excellent tool for visualizing and evaluating the condition of the synovium macroscopically. On arthroscopic examination, precise evaluation of the villi often provides clues, enabling accurate diagnosis. In addition, histological sections obtained from biopsy specimens in various cases of synovitis give significant information. In this article, arthroscopic observation and histological sections of various cases of synovitis are compared, and the diagnostic value and limitations of arthroscopic examination are discussed. Key Words: Synovitis-Arthritis-Diagnostics.
ovium, and pronounced villi formation is not generally observed. The normal synovium is translucent at the surface, and the vascular network with fine villi formation can be seen (1) (Fig. 1). Classification of the shape of the villi by Iino, one of the pioneers of arthroscopy, is shown in Fig. 2 (l-4). The villi usually observed in the normal synovium are feather-like, slender, rounded, or thinly membranous. Histologically, one to three layers of synoviocytes are loosely packed with an intercellular matrix in the surface and form the lining layer. The intercellular matrix consists of fine filamentous material and is sparsely distributed; therefore, the tine vascular network undeneath the lining layer can be easily observed (Fig. 3). Historically, in the knee joint the synovium is classified into three different types: fibrous synovium, areolar synovium, or adipose synovium. Fibrous synovium is characterized by few villi, a fine vascular network, and abundant fibrous connective tissue in the sublining layer. This type of synovium is often seen in the suprapatellar bursa. Areolar synovium is characterized by thin membranous villi and a loop-shape vascular network and is believed to reflect the synovial pathology precisely. This type is seen in the suprapatellar recesses. Adipose synovium is yellowish in color, is characterized by abundant adipose tissue, and is observed on the infrapatellar fat pad.
Embryologically, the joint space is understood as the space created in connective tissue. The synovium underlying this space is richly vascular without a basement membrane, and therefore chemical mediators in the blood may be transported easily into the synovial tissue and as a result synovitis may develop. Because the synovial appearance (synovitis) closely reflects the pathological condition (arthritis) of the knee joints, it is essential to evaluate the condition of the synovium both macroscopically and microscopically. Arthroscopy is the best way to visualize and evaluate the condition of the synovium macroscopically. In this article, we will compare the arthroscopic appearance and the histological sections of the various types of synovitis and discuss the diagnostic value and limitations of arthroscopic examination.
NORMAL SYNOVIUM Under arthroscopic examination, there is a minor variation in the shape of the surface of the synFrom the Department of Orthopaedic Surgery, Kobe University School of Medicine, Kobe, and *Department of Orthopaedic Surgery, Sanda Municipal Hospital, Sanda, Japan. Address correspondence and reprint requests to Dr. M. Kurosaka at Department of Orthopedic Surgery, Kobe University School of Medicine, 7-5-2 Kusunoki-cho, Chuo-ku, Kobe 650, Japan.
162
lA,B
FIG. 1. There is a minor variation in the shape of the surface of the normal synovium. The normal synovium is translucent at the surface; thus, the vascular network can be observed. A: Suprapatellar recess. B: Suprapatellar bursa. C: Meniscosynovial junction. D: Intercondylar space.
lC,D
T
!
I Slender
Rounded
Thin membranous
Thick membranous
Mass-like
I
Anterior
Side
I
x-n
view
L3 I
JLLL
view
%
View in cross section
00
$0 0:
0
0
l 0 I
I Other
Fringe-like
1
Polyp-like
1
Clubbed
1
Twig-like
forms
nJx FIG. 2. Schema for description
of some typical forms of the villi. Reproduced
@!W with permission from (I 1.
FIG. 3. One to three layers of lining cells are loosely pa eked with intercellular matrix in the lining layer. Note the tine tilamentous material facing joint space (arrows). JS, joint spat :e.
FIG. 4. Arthroscopic view of suprapatellar bursa shows thte dilatation and hyperemia of blood vessels caused by reactiv’ e synovitis (A). B: Vasospasms and ischemia after injection of 0.05 mg epinephrine into the joint cavity.
TABLE 1. Types of synovitis in arthritides Etiology of synovitis
Villi shape
Vascular pattern
Slender, thin membranous Thick membranous, polyp-like, fringe-like Thick membranous, polyp-like, club-shaped, edematous Exudative changes
Normal
Thick membrane, grayish in appearance
Minimal
Psoriatic synovitis
Mild villi formation
Normal
Reiters syndrome
Formation not pronounced
Prominent
Behcet’s syndrome
Thick membranous fringe-like
Synovitis of pustulosis palmaris et plantaris
Reddish, clubbed-shape, edematous
Trauma or osteoarthritis Osteoarthritis
Rheumatoid arthritis Active, chronic, inflammatory synovitis Suppurative synovitis
Tuberculous
synovitis
Clearly visible
Histologic features Minimal thickening of lining-infiltrate of lymphocytes and plasma cells Mild thickening of lining-infiltrate of inflammatory cells
Difficult to see, marked increase in vessels
Marked thickening of the lining; edema is prominent with proliferation of inflammatory cells with necrotic changes
Not observable, bleeding, debris
Lining cells do not proliferate; congestion and dilatation of the vessels-leukocytic infiltrate with edema Thickening of the lining with little vascular proliferation; prominent epithelial and Langhans’ giant cells around caseous necrosis No lining proliferation; lymphoid follicles common Lining cells proliferate with lymphocytes and plasma cells; no thickening of the fibrous connective tissue; marked increase in vascular network Proliferation of lining cells with infiltration of plasma cells and lymphocytes; minima1 vascular proliferation and thickening of fibrous connective tissue Moderate proliferation of lining cells and inflammatory infiltration; no thickening of the fibrous connective tissue
or
Not visible
FIG. 5. Top: Arthroscopic observation of medial synovial shelf shows proliferation of villi. Bottom: Histological examination of the synovial shelf revealed a focal infiltration of lymphocytes. This is one of the extreme cases of reactive synovitis caused by medial shelf syndrome.
FIG. 6. Top: Arthroscopic appearance of the synovium of osteoarthritis shows thin membranous villi and vascular network. Bottom: Nonspecific synovitis with mild infiltration of the inflammatory cells and proliferation of lining cells are observed histologically.
M. KUROSAKA
166
FIG. 7. Suppurative arthritis. Top: The synovium is markedly edematous, congested, and bleeds easily. Bottom: Histologically, suppurative coating consisting of fibrin and erythrocytes is observed. In the interstitial tissue, a number of polymorphonuclear cells infiltrate, and inflammatory edema exists.
Because the synovium is not a dense fibrous tissue, it becomes congested and edematous during prolonged arthroscopic examination; therefore, assessment should be done immediately (43. Also, the color of the normal synovium is much influenced by the intraarticular injection of small amounts of vasoconstrictors (Fig. 4). However, synovial color is not influenced by vasoconstrictors when inflammatory changes such as congestion and edema exist. It is sometimes useful to use vasoconstrictors to differentiate pathological synovitis from noninflammatory congestion of the vascular network. SYNOVIUM IN VARIOUS ARTHRITIDES Although pathological Arthroscopy,
there is significant variation in the condition of the synovium, in this ar-
Vol. 7, No. 2, 1991
ET AL.
FIG. 8. Top: Arthroscopic view of the synovium shows early stage of rheumatoid arthritis (RA). The congestion of blood vessels and slight edematous swelling of synovium are observed. Bottom: Histologically, nonspecific inflammatory change can be seen. It is difficult to make a definite diagnosis of RA at this stage.
title we will discuss the arthroscopic appearance of various types of synovitis in conjunction with their histological observation (Table 1). The types of synovitis to be discussed are reactive synovitis (traumatic synovitis and osteoarthritis), suppurative synovitis, tuberculous synovitis, rheumatoid synovitis, and synovitis caused by rheumatoid allied diseases.
REACTIVE SYNOVITIS In traumatic synovitis, except for the very acute phase immediately after the trauma, proliferation of the villi is the only finding observed during arthroscopy. However, the shape of the villi is not significantly different from that of the normal synovium, and arthroscopic observation does not provide us with specific information (Fig. 5). This is also true for the histological observation. Usually there is a
EVALUATION
OF SYNOVITIS
FIG. 9. Top: Arthroscopic appearance of the synovium shows opaque, hyperemic, and edematous swelling of villi and represents the exudative inflammatory change. Bottom: Marked infiltration of lymphocytes and plasma cells are found histologically.
minimal thickening of the lining layer and some infiltration of lymphocytes and plasma cells, which is characteristic of nonspecific synovitis. Occasionally, focal infiltration of lymphocytes is observed, but there are few cells and the vascular network in the lining layer is easily identified. In the synovium of osteoarthritis, the degree of villi formation is greater than that of traumatic synovitis and the shape of the villi can vary. A thick membranous shape, a fringe-like shape, or a polyplike shape occur, but usually the villi are not edematous (Fig. 6). The histological appearance is also characterized as nonspecific synovitis with mild proliferation and thickening of the lining layer and a mild infiltration of the inflammatory cells.
IN KNEE
FIG. 10. Top: Arthroscopic view of the synovium shows the granulation stage of rheumatoid arthritis. The villi of this type have a mixture of grayish and purple-red color, indicating the patchy distribution of the granulation tissue in the synovium. Note the form of villi, which is not edematous. Bottom Histological examination reveals infiltration of lymphocytes and plasma cells accompanied by proliferation of fibrous connective tissues.
ily. Also, a suppurative exudate is attached to the surface of the synovium, and the joint space itself becomes smaller. Therefore, arthroscopic observation is not always easy because the synovium is not translucent in suppurative arthritis and the vascular network cannot be examined (Fig. 7). Histologically, congestion and dilatation of the vessels are found in the lining and sublining layer. In the interstitial tissue, polymorphonuclear leukocytic infiltrate and inflammatory edema exist. However, the synoviocytes in the lining layer do not usually proliferate. RHEUMATOID
SUPPURATIVE
167
ARTHRITIS
(RA)
ARTHRITIS
In this type of synovitis, the synovium becomes markedly edematous. is congested, and bleeds eas-
The histological appearance of the synovium in RA varies widely with exudation, inflammatory cell infiltration, and granulation depending on the stage Arthroscopy,
Vol. 7. No. 2, 1991
M. KUROSAKA ET AL.
168
FIG. 11. Tuberculous synovitis. Top: Under arthroscopic examination, there are necrotic shreds and white granulation-like tissue. Bottom: Histological specimen shows the granulomatous change with proliferation of epithelioid cells.
of the disease. In the earliest stage of RA, a reddish color change of the synovium caused by congestion is the only finding seen on arthroscopic examination (Fig. 8). Infiltration of the inflammatory cells is less, and mild proliferation of the capillary vessels in the lining layer is the only finding even in the histological examination. It is difficult to make a definite diagnosis of RA at this stage because the abovementioned characteristics are often diagnosed as nonspecific monoarthritis. Once the disease advances, certain specific findings are present. The villi are fringe-like, polyp-like, clubbed, or twig-like and are prominent and often edematous (1). Edematous changes of the synovium commonly represent the exudative stage. Because of this exudative change, the surface of the synovium is covered by fibrin deposits (Fig. 9). In addition, marked proliferation of inflammatory cells and necrotic changes (4) in the synovium make the observation of the vascular network difficult. When the disease advances further, villi without Arthroscopy,
Vol. 7, No. 2, 1991
FIG. 12. Top: Arthroscopic appearance of psoriatic synovitis is similar to that of the early stage of reheumatoid arthritis with slight edematous swelling and hyperemia of synovium. Bottom: Histologically, proliferation of the lining cells is less. Note that the lymphoid follicle that is often encountered in psoriatic synovitis.
edema representing the formation of granulation can be seen. Villi of this type shown in Fig. 10 are a mixed grayish and purple-red color. Infiltration of lymphocytes and plasma cells and proliferation of fibrous connective tissue are found in the histological specimen of these villi.
TUBERCULOUS
SYNOVITIS
Tuberculous synovitis is the typical form of granulomatous inflammation. Histologically, this is the focal proliferative change characterized by rapid growth of the epithelioid cells and Langhans’ giant cells around the caseous necrosis. Although the histological appearance is uniformly characteristic, arthroscopic appearance of this type of synovitis is not necessarily uniform. In the very early stage, it is common that only minimal changes can be found in
EVALUATION
OF SYNOVITIS
FIG. 13. Reiter’s syndrome. Top: Arthroscopic appearance of the synovium shows hyperemia and bleeding of the vascular network. Bottom: Histologically, proliferation of the lining cells, and increased vascular network and infiltration of lymphocytes and plasma cells, are seen.
the synovium. However, once the disease advances, the lining layer of the synovium thickens with little vascular proliferation. At arthroscopy the synovium looks grayish and anemic (1) (Fig. 11). In addition, various findings such as marked fibrin deposition, deposition of material secreted from caseous degeneration, or a nonspecific mild form of synovitis may be seen. Therefore, at the time of arthroscopic examination it is crucial to make a thorough observation and take biopsy specimens from the different parts of the synovium (1) to avoid misdiagnosis.
OTHER TYPES OF SYNOVITIS Psoriatic synovitis When arthritis precedes dermatitis, diagnosis is often very difficult. There are no specific arthroscopic findings with this synovitis. Usually, psori-
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FIG. 14. Behcet’s syndrome. The shape of the vihi is thick membranous or fringe-like. Top: The arthroscopic findings are similar to that of the granulation stage of rheumatoid arthritis. Bottom: Histologically, proliferation of the lining cells and infiltration of lymphocytes and plasma cells are evident.
atic synovitis is very similar to reactive synovitis, with very mild villi formation and a normal vascular network (Fig. 12). Histologically, there is no proliferation of the synoviocytes in the lining layer and no infiltration of macrophages. However, formation of the lymphoid follicle is often encountered. Synovitis of Reiter’s syndrome In the early stage of this synovitis, the arthroscopic findings are similar to those found in suppurative arthritis. However, with progression of the disease, this synovitis closely resembles rheumatoid synovitis. Figure 13 shows the increased vascular network, congestion, and bleeding observed in the early phase. Here, the synovium becomes thickened with edema, bleeds easily, and villi formation is not pronounced. Histologically, marked inflammatory findings are seen with proliferation of the synoviocytes, an increased vascular network, and infiltration of lymphocytes and plasma cells. It is characteristic that thickening of fibrous connecArthroscopy.
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M.KUROSAKAETAL. not usually seen. In the arthroscopic examination the villi are reddish, clubbed, and edematous. Occasionally, spotty bleeding is found on the surface and the vascular network is not visible (Fig. 15). Histologically, nonspecific inflammatory changes such as moderate proliferation of synoviocytes and infiltration of inflammatory cells may be seen. Usually there is no thickening of the fibrous connective tissue (Fig. 14). CONCLUSIONS
FIG. 15. Pustulosis palmaris et plantaris. Top: Under arthroscopic examination the villi are reddish, clubbed, and edematous. Note the capillary bleeding. Bottom: Histologically, nonspecific inflammatory changes can be seen.
tive tissue is not seen in the deep layer of the synovium. Synovltis of Behcet’s syndrome In this syndrome, approximately one-half of the patients have an episode of arthritis. On arthroscopic observation the synovium resembles that of the granulation stage of RA. The villi are usually thick membranous or fringe-like. Because no edematous change or vascular network is seen, the surface of the synovium is somewhat grayish (Fig. 14). Histologically, there are a proliferation of synoviocytes, infiltration of lymphocytes and plasma cells, and thickening of fibrous connective tissue. Synovitis of pustulosis palmaris et plantaris The synovitis of this disease characteristically shows exacerbation with significant effusion and remission. Nevertheless, destruction of the joint is Arthroscopy, Vol. 7, NO. 2, 1991
On arthroscopic examination, it is essential to evaluate the shape of the villi, the color of the synovium, the vascular network, and the edematous changes. It is crucial to decide whether the villi are edematous or not. If the villi are not edematous and are slender or thin membranous in shape, reactive synovitis caused by trauma or osteoarthritis is most likely. Thick membranous, polyp-like, or conus-like villi without edema suggest a proliferative process. When villi of this proliferative type show a clearly visible vascular network, synovitis caused by osteoarthritis in which cellular infiltration is minimal should be considered. On the other hand, when the vascular network is not observed in villi of the proliferative type, active, chronic, inflammatory synovitis such as RA should be suspected. When the villi are edematous with exudative changes and with a marked cellular infiltration, the vascular network cannot be observed in most cases. The edematous synovium with bleeding, exudation, and debris typically represents suppurative synovitis. In conclusion, arthroscopic examination of various types of synovitis gives significant information. When the diagnosis of monoarthritis is not certain, arthroscopic examination and synovial biopsy should be considered. On arthroscopic examination, precise evaluation of the villi often provides a clue to the diagnosis. REFERENCES 1. Watanabe M, Takeda S, Ikeuchi H. Atlas of arthroscopy, 2nd ed. Tokyo: Igaku Shoin, 1969. 2. Iino S. Normal arthroscopic findings of the knee joints in adults. J Jpn Orthop Assoc 1939;14:467-518. 3. Ikeuchi H. Normal arthroscopic findings of the knee joints. Instructional course lecture-I. Arthroscopy 1977;2:5744. 4. Ikeuchi H. In aid of understanding arthroscopic findings. Arthroscopy
1982;7:93-5.
5. Watanabe M. Arthroscopic findings of various pathological conditions in knee joints. Instructional course lecture-II. Arthroscopy
1977;2:65-73.
