CKn, RadioL (1975) 26, 357-361
PIGMENTED
VILLO-NODULAR
SYNOVITIS: OF THE FINGERS
BONE
INVOLVEMENT
S. DAVIS, G. L A W T O N and M. LOWY
From the Departments of Radiology and Orthopaedics, Royal Northern Hospital, London Pigmented villo-nodular synovitis may occur in either diffuse or nodular form. In the latter the fingers are the commonest sites to be involved. The disease is rare, and in only 15 ~ is there bone involvement. Two cases showing bone involvement of the fingers are presented. One of the cases (Case 2) adds radiological support to the theory of Scott (1968), based on pathological studies, that suggested that the bone changes are due to invasion by the villo-nodular tissue through and along the nutrient foramina. The site of these bone changes appears sufficiently typical to be a radiological diagnostic aid. The differential diagnosis of the radiological appearances of the disease in the digits is discussed.
NUMEROUS synonyms are used for pigmented villo-nodular synovitis and this has caused much confusion in the past. Other terms for this condition include benign synovioma, xanthona, giant cell tumour, villous arthritis and myelo-xanthoma. Probably the first case involving the digits was described by Chassaignac (1852), who reported lesions of nodular form arising in relation to the flexor tendon sheaths of the middle and index fingers. The term pigmented villo-nodular synovitis was introduced in 1941 by Jaffe et al. to describe this condition of unknown aetiology in which the synovial membrane of a joint becomes diffusely or locally thickened. They described a similar change occurring in the synovium of tendon sheaths and bursae and suggested that it represented an inflammatory response to an unknown agent. Clinically, the disease affects persons of early middle life, affecting females slightly more often than males (Atmore et al., 1956). Two forms are described, and in both forms the disease is usually mon-articular. The diffuse form of the disease may affect the knees, hips, ankle sub-talar joints, elbows, shoulders and carpus. The fingers are the commonest sites of the nodular form, the palmar aspect being much more frequently involved than the dorsal aspect. A slowly progressive swelling, usually non-tender on palpation, and only rarely painful, is the usual presentation. The synovium varies in colour with the iron content from yellow and red to dark brown. Histological examination shows marked proliferation of the surface cells and the connective tissue throughout the synovial membrane, together with an accumulation ofintraceUular and extracellular haemosiderin and lipoid material,
FIG. 1 (Case 1) The left first metacarpal shows irregular porosis of cortex and medulla extending across the entire width of the bone. A periosteal reaction has developed consequent to the pathological fracture.
357
358
CLINICAL RADIOLOGY
associated with a n a b u n d a n c e o f r e t i c u l o - e n d o t h e l i a l cells including giant cells (Scott, 1968). T h e radiological changes have been described b y Lewis (1947), Breimer a n d F r e i b e r g e r (1958) a n d Smith a n d P u g h (1962). I n m o s t cases there is soft tissue involvement only. Byers et al. (1968) n o t e d b o n e involvement in 15 %. Smith and Pugh (1962), in their series o f 202 cases, had 164 cases involving
the knee b u t n o n e involved the fingers. Byers et al. (1968), however, n o t e d t h a t the fingers were affected in one-third o f their cases.
FIG. 2 (Case 1) Histological section of the tissue obtained from the first metacarpal (high power). The changes are typical of pigmented villo-nodular synovitis. A number of giant reticuloendothelial cells are shown together with an accumulation of haemosiderin and lipoid material.
FIG. 3 (Case 2) Lateral view of the right index finger. There is a well-defined translucent lesion in the lower half of the middle phalanx with bone fragments 'lifted off' the palmar aspect of the phalanx. Soft-tissue swelling is present.
CASE REPORTS Case 1. - Male, aged 53 years, who presented with swelling of the left thumb in the region of the metacarpal bone. His main complaint was of restricted movement of this digit and
PIGMENTED
VILLO-NODULAR
SYNOVITIS:
occasional pain. The lump was slightly tender and all symptoms bad increased slowly. The radiological appearances (Fig. 1) show an irregular porosis of both medulla and cortex with a pathological fracture of the left first metacarpal and a periosteal reaction surrounding this area. Soft-tissue swelling is present. A full skeletal survey was negative and an open biopsy was performed. A considerable amount of vascular tissue had replaced much of the metacarpal, and the histological section is shown in Fig. 2. The appearances were those of pigmented villo-nodular synovitis. The patient made an uneventful recovery. Case 2. - Female, aged 51 years, who presented with a 6 months' history of slowly progressive swelling of the right index finger. Examination showed a swelling on the ulnar aspect of the middle phalanx of the finger, which was not tender or inflamed and moved normally. The radiographs (Figs. 3 and 4) show a well-defined translucent defect with a corresponding soft-tissue swelling. The lesion has a very faint rim of sclerosis and a clean-cut endosteal border. The lateral view is particularly interesting in that it shows small portions of bone lying anteriorly, entirely separate from the phalanx. The appearances suggest that the space-occupying lesion within the bone has forced out that portion of bone lying anterior t ° the nutrient foramen. Histological examination showed the typical changes of pigmented villo-nodular synovitis (Figs. 5, 6). Subsequent recovery was uneventful.
BONE
INVOLVEMENT
OF THE
FINGERS
359
involves one bone, though elsewhere it occasionally involves more than one joint (Gehweiler and Wilson, 1969). Resistance of the joint cartilage for a long period is typical of the condition and the neighbouring bone is not decalcified. The joint space is rarely decreased. The metacarpals or phalanges m a y be involved, but the carpal and tarsal bones are only rarely affected in the nodular form. The defect itself is usually well defined with a clear-cut edge without sclerosis, or with only a minimal sclerotic edge. Usually best shown in the postero-anterior projection (Fig. 4), the appearance m a y be characteristic; the lesion is situated on either the ulnar or radial aspect of the bone, with sharply defined borders. A very similar example in the posteroanterior projection is shown by Campbell Golding (1971). The lateral view in this condition may also be characteristic. It can be seen in Fig. 3 that in addition to the characteristic intra-osseous defect, portions of bone have been elevated from the shaft
DISCUSSION Scott (1968) suggested that the bone lesions are not the result of direct external pressure, as in the case of aneurysms or extra-osseous tumours, but that invasion of bone takes place t h r o u g h the vascular foramina underlying the diseased synovium. He further suggested that villo-nodular tissue carrying its own blood supply grows into these foraminae alongside the nutrient vessels. The tissue expands the foraminae and, following the path of least resistance along the course o f the osseous vessels, passes deeply into bone where its growth produces pressure atrophy, resulting in intra-osseous cysts. Radiologically this is clearly very important since translucent defects in bone, n o t following the line o f the nutrient foramina or well away from the nutrient foramina, are unlikely to be due to pigmented villo-nodular synovitis. The bone lesion is basically a translucent, well-defined area, associated with a soft-tissue mass. The soft-tissue mass is an important feature and is always present if bone is affected. The diagnosis of pigmented villonodular synovitis is not feasible in the bones o f the digits in the absence of a swelling extending outside the joint capsule. The lobulated soft-tissue mass may appear dense, since it contains haemosiderin. It does n o t usually contain calcium. In the small bones of the hands and feet, the lesion usually only
FIo. 4. (Case 2) Postero-anterior and oblique views. The oblique film suggests that the lesion is within the medulla but the P-A film shows the lesion in profile, and the typical appearance of bone invasion from pigmented villo-nodular synovitis is seen.
360
CLINICAL RADIOLOGY
of the phalanx and are lying separated from the palmar aspect o f the main bone. This appearance is consistent with invasion and expansion along the nutrient foramina. A very similar lateral view appearance without the bone lifted off is shown by Jacobs (1973). The radiological appearances of the second case are sufficiently typical to suggest the correct pre-operative diagnosis. The radiographs of the first case, however, did not show any of the characteristic features of pigmented villo-nodular synovitis, and the periosteal reaction shown in these films appears to be explained by the pathological fracture, since a periosteal reaction is not a feature of this condition and the diagnosis was not made before the histologieal sections were examined. In the digits the differential diagnosis is moder-
ately wide, depending on the site and appearance of the individual lesion. The dermoid or epidermoid cyst is usually found in the terminal phalanx of adolescents or adults and appears in the fourth decade. There is often a history of trauma, although there may be a long history between the injury and detection of the cyst. Some cases may arise spontaneously. Men are affected more than women and the lesion is usually in the centre of the phalanx. It removes a circular or oval piece of bone without a periosteal reaction. The glomus tumour is radiologically indistinguishable from an implantation dermoid (Jacobs, 1973). They may extend to cause much destruction of distal phalanges. Secondary deposits may involve the digits, but they are usually more destructive and irregnlar in their
Fie. 5. (Case 2) Histological section (low power) showing the typical appearance of pigmented villo-nodular synovitis. There is proliferation of the surface cells and connective tissue throughout the synovial membrane.
F~. 6 (Case 2) Histological section (high power). There is an accumulation of haemosiderin and lipoid material in a rcticulo-endothelial giant cell.
PIGMENTED
VILLO-NODULAR
SYNOVITIS:
outer margins. M y e l o m a m a y have quite welldefined clear-cut margins, t h o u g h usually they appear as circular areas eroding the cortex f r o m within. The e n c h o n d r o m a is p r e d o m i n a n t l y intram e d u l l a r y t h o u g h it m a y b r e a k the cortex, a n d calcification m a y occur within it. T h e c h o n d r o myxoid f i b r o m a m a y be f o u n d in small t u b u l a r bones a n d the lesions tend to be m o r e Central with thinning o f the cortex, which m a y be e x p a n d e d b u t is usually preserved. T h e centre o f the turnout is usually clear. A n a n e u r y s m a l b o n e cyst m a y also be f o u n d in the small t u b u l a r bones b u t a gross periosteal ' b l o w - o u t ' is a feature o f this disease a n d a m u l t i l o c u l a r a p p e a r a n c e is usual. Unlikely to cause m u c h difficulty in diagnosis is t h e whitlow when t h e lesion involves the t e r m i n a l phalanx. Other lesions to be considered are tuberculous dactylitis, sarcoid a n d syphilis. G o u t is unlikely to cause any difficulty if multi-centric and, similarly, an a n g i o m a t o u s m a l f o r m a t i o n is unlikely to be missed clinically. Very rarely other lesions m a y have to be considered, b u t in the typical case, as in our second patient, the radiological features are sufficient to enable a confident p r e - o p e r a t i v e diagnosis.
Acknowledgements. - We wish to thank Dr A. E. Brewer and Dr M. Peters for their help and advice with the histology slides, and we wish to acknowledge the secretarial staff of the X-ray Department of the Royal Northern Hospital, London.
24
BONE I N V O L V E M E N T
OF THE FINGERS
361
REFERENCES ATMORE, W. G., DAHLIND. C. & GHORMLEY, R. K. (1956),
Pigmented villo-nodular synovitis: clinical and pathologic study. Minnesota Medicine, 39, 196-202. BREIMER, C. W. & FREIBERGER,R. H. (1958). Bone lesions associated with villo-nodular synovitis. American Journal of Roentgenology, 79, 618-629. BYERS, P. D., COTTON, R_ E., DEACON, O. W., LowY, M., NEWMAN, P. H., SISSoNS, H. A. & THOMSON, A. D. (1968). The diagnosis and treatment of villo-nodular synovitis. Journal of Bone and Joint Surgery, 50B (2), 290-311. CAMPBELLGOLDING, F. (1971). A Textbook of X-ray Diagnosis, Vol. 6, p. 492. H. K. Lewis & Co., London. CHASSAIGNAC,E. P. M. (1852). Cancer de la Gaine des Tendons. Gazette des Hopitaux Civils et Militaires, 25, 185-186. GEHWEILER,J. A. & WILSON,J. W. (1969). Diffuse biarticular pigmented villo-nodular synovitis. Radiology, 93, 845-851. JACOBS, P. (I973). Atlas of Hand Radiographs. Harvey, Miller and Medcalf, London. JAFFE, H. L., LICHTENSTEIN, L. & SUTRO, C. J. (1941). Pigmented villo-nodular synovitis, bursitis and tenosynovitis : discussion of synovial and bursal equivalents of tenosynovial lesion commonly denoted as xanthoma, xanthogranuloma, giant cell tumour or rnyeloplaxoma of tendon sheath, with some consideration of this tendon sheath lesion itself. Archives of Pathology, 31,731-765. LEWIS, R. W. (1947). Roentgen diagnosis of pigmented villonodular synovifis and synovial sarcoma of knee joint: preliminary report. Radiology, 49, 26-38. SCOTT, P. M. (1968). Bone lesions in pigmented villonodular synovitis. Journal of Bone and Joint Surgery, 50B, 306-311. SMITH, J. H. & PUGH, D. G. (1962). Roentgenographic aspects of articular pigmented villo-nodular synovitis. American Journal of Roentgenology, 87, 1146-1156.
PIGMENTED
VILLO-NODULAR
SYNOVITIS: OF THE FINGERS
BONE
INVOLVEMENT
S. DAVIS, G. L A W T O N and M. LOWY
From the Departments of Radiology and Orthopaedics, Royal Northern Hospital, London Pigmented villo-nodular synovitis may occur in either diffuse or nodular form. In the latter the fingers are the commonest sites to be involved. The disease is rare, and in only 15 ~ is there bone involvement. Two cases showing bone involvement of the fingers are presented. One of the cases (Case 2) adds radiological support to the theory of Scott (1968), based on pathological studies, that suggested that the bone changes are due to invasion by the villo-nodular tissue through and along the nutrient foramina. The site of these bone changes appears sufficiently typical to be a radiological diagnostic aid. The differential diagnosis of the radiological appearances of the disease in the digits is discussed.
NUMEROUS synonyms are used for pigmented villo-nodular synovitis and this has caused much confusion in the past. Other terms for this condition include benign synovioma, xanthona, giant cell tumour, villous arthritis and myelo-xanthoma. Probably the first case involving the digits was described by Chassaignac (1852), who reported lesions of nodular form arising in relation to the flexor tendon sheaths of the middle and index fingers. The term pigmented villo-nodular synovitis was introduced in 1941 by Jaffe et al. to describe this condition of unknown aetiology in which the synovial membrane of a joint becomes diffusely or locally thickened. They described a similar change occurring in the synovium of tendon sheaths and bursae and suggested that it represented an inflammatory response to an unknown agent. Clinically, the disease affects persons of early middle life, affecting females slightly more often than males (Atmore et al., 1956). Two forms are described, and in both forms the disease is usually mon-articular. The diffuse form of the disease may affect the knees, hips, ankle sub-talar joints, elbows, shoulders and carpus. The fingers are the commonest sites of the nodular form, the palmar aspect being much more frequently involved than the dorsal aspect. A slowly progressive swelling, usually non-tender on palpation, and only rarely painful, is the usual presentation. The synovium varies in colour with the iron content from yellow and red to dark brown. Histological examination shows marked proliferation of the surface cells and the connective tissue throughout the synovial membrane, together with an accumulation ofintraceUular and extracellular haemosiderin and lipoid material,
FIG. 1 (Case 1) The left first metacarpal shows irregular porosis of cortex and medulla extending across the entire width of the bone. A periosteal reaction has developed consequent to the pathological fracture.
357
358
CLINICAL RADIOLOGY
associated with a n a b u n d a n c e o f r e t i c u l o - e n d o t h e l i a l cells including giant cells (Scott, 1968). T h e radiological changes have been described b y Lewis (1947), Breimer a n d F r e i b e r g e r (1958) a n d Smith a n d P u g h (1962). I n m o s t cases there is soft tissue involvement only. Byers et al. (1968) n o t e d b o n e involvement in 15 %. Smith and Pugh (1962), in their series o f 202 cases, had 164 cases involving
the knee b u t n o n e involved the fingers. Byers et al. (1968), however, n o t e d t h a t the fingers were affected in one-third o f their cases.
FIG. 2 (Case 1) Histological section of the tissue obtained from the first metacarpal (high power). The changes are typical of pigmented villo-nodular synovitis. A number of giant reticuloendothelial cells are shown together with an accumulation of haemosiderin and lipoid material.
FIG. 3 (Case 2) Lateral view of the right index finger. There is a well-defined translucent lesion in the lower half of the middle phalanx with bone fragments 'lifted off' the palmar aspect of the phalanx. Soft-tissue swelling is present.
CASE REPORTS Case 1. - Male, aged 53 years, who presented with swelling of the left thumb in the region of the metacarpal bone. His main complaint was of restricted movement of this digit and
PIGMENTED
VILLO-NODULAR
SYNOVITIS:
occasional pain. The lump was slightly tender and all symptoms bad increased slowly. The radiological appearances (Fig. 1) show an irregular porosis of both medulla and cortex with a pathological fracture of the left first metacarpal and a periosteal reaction surrounding this area. Soft-tissue swelling is present. A full skeletal survey was negative and an open biopsy was performed. A considerable amount of vascular tissue had replaced much of the metacarpal, and the histological section is shown in Fig. 2. The appearances were those of pigmented villo-nodular synovitis. The patient made an uneventful recovery. Case 2. - Female, aged 51 years, who presented with a 6 months' history of slowly progressive swelling of the right index finger. Examination showed a swelling on the ulnar aspect of the middle phalanx of the finger, which was not tender or inflamed and moved normally. The radiographs (Figs. 3 and 4) show a well-defined translucent defect with a corresponding soft-tissue swelling. The lesion has a very faint rim of sclerosis and a clean-cut endosteal border. The lateral view is particularly interesting in that it shows small portions of bone lying anteriorly, entirely separate from the phalanx. The appearances suggest that the space-occupying lesion within the bone has forced out that portion of bone lying anterior t ° the nutrient foramen. Histological examination showed the typical changes of pigmented villo-nodular synovitis (Figs. 5, 6). Subsequent recovery was uneventful.
BONE
INVOLVEMENT
OF THE
FINGERS
359
involves one bone, though elsewhere it occasionally involves more than one joint (Gehweiler and Wilson, 1969). Resistance of the joint cartilage for a long period is typical of the condition and the neighbouring bone is not decalcified. The joint space is rarely decreased. The metacarpals or phalanges m a y be involved, but the carpal and tarsal bones are only rarely affected in the nodular form. The defect itself is usually well defined with a clear-cut edge without sclerosis, or with only a minimal sclerotic edge. Usually best shown in the postero-anterior projection (Fig. 4), the appearance m a y be characteristic; the lesion is situated on either the ulnar or radial aspect of the bone, with sharply defined borders. A very similar example in the posteroanterior projection is shown by Campbell Golding (1971). The lateral view in this condition may also be characteristic. It can be seen in Fig. 3 that in addition to the characteristic intra-osseous defect, portions of bone have been elevated from the shaft
DISCUSSION Scott (1968) suggested that the bone lesions are not the result of direct external pressure, as in the case of aneurysms or extra-osseous tumours, but that invasion of bone takes place t h r o u g h the vascular foramina underlying the diseased synovium. He further suggested that villo-nodular tissue carrying its own blood supply grows into these foraminae alongside the nutrient vessels. The tissue expands the foraminae and, following the path of least resistance along the course o f the osseous vessels, passes deeply into bone where its growth produces pressure atrophy, resulting in intra-osseous cysts. Radiologically this is clearly very important since translucent defects in bone, n o t following the line o f the nutrient foramina or well away from the nutrient foramina, are unlikely to be due to pigmented villo-nodular synovitis. The bone lesion is basically a translucent, well-defined area, associated with a soft-tissue mass. The soft-tissue mass is an important feature and is always present if bone is affected. The diagnosis of pigmented villonodular synovitis is not feasible in the bones o f the digits in the absence of a swelling extending outside the joint capsule. The lobulated soft-tissue mass may appear dense, since it contains haemosiderin. It does n o t usually contain calcium. In the small bones of the hands and feet, the lesion usually only
FIo. 4. (Case 2) Postero-anterior and oblique views. The oblique film suggests that the lesion is within the medulla but the P-A film shows the lesion in profile, and the typical appearance of bone invasion from pigmented villo-nodular synovitis is seen.
360
CLINICAL RADIOLOGY
of the phalanx and are lying separated from the palmar aspect o f the main bone. This appearance is consistent with invasion and expansion along the nutrient foramina. A very similar lateral view appearance without the bone lifted off is shown by Jacobs (1973). The radiological appearances of the second case are sufficiently typical to suggest the correct pre-operative diagnosis. The radiographs of the first case, however, did not show any of the characteristic features of pigmented villo-nodular synovitis, and the periosteal reaction shown in these films appears to be explained by the pathological fracture, since a periosteal reaction is not a feature of this condition and the diagnosis was not made before the histologieal sections were examined. In the digits the differential diagnosis is moder-
ately wide, depending on the site and appearance of the individual lesion. The dermoid or epidermoid cyst is usually found in the terminal phalanx of adolescents or adults and appears in the fourth decade. There is often a history of trauma, although there may be a long history between the injury and detection of the cyst. Some cases may arise spontaneously. Men are affected more than women and the lesion is usually in the centre of the phalanx. It removes a circular or oval piece of bone without a periosteal reaction. The glomus tumour is radiologically indistinguishable from an implantation dermoid (Jacobs, 1973). They may extend to cause much destruction of distal phalanges. Secondary deposits may involve the digits, but they are usually more destructive and irregnlar in their
Fie. 5. (Case 2) Histological section (low power) showing the typical appearance of pigmented villo-nodular synovitis. There is proliferation of the surface cells and connective tissue throughout the synovial membrane.
F~. 6 (Case 2) Histological section (high power). There is an accumulation of haemosiderin and lipoid material in a rcticulo-endothelial giant cell.
PIGMENTED
VILLO-NODULAR
SYNOVITIS:
outer margins. M y e l o m a m a y have quite welldefined clear-cut margins, t h o u g h usually they appear as circular areas eroding the cortex f r o m within. The e n c h o n d r o m a is p r e d o m i n a n t l y intram e d u l l a r y t h o u g h it m a y b r e a k the cortex, a n d calcification m a y occur within it. T h e c h o n d r o myxoid f i b r o m a m a y be f o u n d in small t u b u l a r bones a n d the lesions tend to be m o r e Central with thinning o f the cortex, which m a y be e x p a n d e d b u t is usually preserved. T h e centre o f the turnout is usually clear. A n a n e u r y s m a l b o n e cyst m a y also be f o u n d in the small t u b u l a r bones b u t a gross periosteal ' b l o w - o u t ' is a feature o f this disease a n d a m u l t i l o c u l a r a p p e a r a n c e is usual. Unlikely to cause m u c h difficulty in diagnosis is t h e whitlow when t h e lesion involves the t e r m i n a l phalanx. Other lesions to be considered are tuberculous dactylitis, sarcoid a n d syphilis. G o u t is unlikely to cause any difficulty if multi-centric and, similarly, an a n g i o m a t o u s m a l f o r m a t i o n is unlikely to be missed clinically. Very rarely other lesions m a y have to be considered, b u t in the typical case, as in our second patient, the radiological features are sufficient to enable a confident p r e - o p e r a t i v e diagnosis.
Acknowledgements. - We wish to thank Dr A. E. Brewer and Dr M. Peters for their help and advice with the histology slides, and we wish to acknowledge the secretarial staff of the X-ray Department of the Royal Northern Hospital, London.
24
BONE I N V O L V E M E N T
OF THE FINGERS
361
REFERENCES ATMORE, W. G., DAHLIND. C. & GHORMLEY, R. K. (1956),
Pigmented villo-nodular synovitis: clinical and pathologic study. Minnesota Medicine, 39, 196-202. BREIMER, C. W. & FREIBERGER,R. H. (1958). Bone lesions associated with villo-nodular synovitis. American Journal of Roentgenology, 79, 618-629. BYERS, P. D., COTTON, R_ E., DEACON, O. W., LowY, M., NEWMAN, P. H., SISSoNS, H. A. & THOMSON, A. D. (1968). The diagnosis and treatment of villo-nodular synovitis. Journal of Bone and Joint Surgery, 50B (2), 290-311. CAMPBELLGOLDING, F. (1971). A Textbook of X-ray Diagnosis, Vol. 6, p. 492. H. K. Lewis & Co., London. CHASSAIGNAC,E. P. M. (1852). Cancer de la Gaine des Tendons. Gazette des Hopitaux Civils et Militaires, 25, 185-186. GEHWEILER,J. A. & WILSON,J. W. (1969). Diffuse biarticular pigmented villo-nodular synovitis. Radiology, 93, 845-851. JACOBS, P. (I973). Atlas of Hand Radiographs. Harvey, Miller and Medcalf, London. JAFFE, H. L., LICHTENSTEIN, L. & SUTRO, C. J. (1941). Pigmented villo-nodular synovitis, bursitis and tenosynovitis : discussion of synovial and bursal equivalents of tenosynovial lesion commonly denoted as xanthoma, xanthogranuloma, giant cell tumour or rnyeloplaxoma of tendon sheath, with some consideration of this tendon sheath lesion itself. Archives of Pathology, 31,731-765. LEWIS, R. W. (1947). Roentgen diagnosis of pigmented villonodular synovifis and synovial sarcoma of knee joint: preliminary report. Radiology, 49, 26-38. SCOTT, P. M. (1968). Bone lesions in pigmented villonodular synovitis. Journal of Bone and Joint Surgery, 50B, 306-311. SMITH, J. H. & PUGH, D. G. (1962). Roentgenographic aspects of articular pigmented villo-nodular synovitis. American Journal of Roentgenology, 87, 1146-1156.
