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Localized pigmented villonodular synovitis presenting as a locked lateral meniscal bucket handle tear: A case report and review of the literature
Arthroscopy: The Journal of Arthroscopic and Related Surgery 10(3):309-312 Published by Raven Press, Ltd. © 1994 Arthroscopy Associationof North America
Case Report
Localized Pigmented Villonodular Synovitis Presenting as a Locked Lateral Meniscal Bucket Handle Tear: A Case Report and Review of the Literature Charles D. Van Meter, M.D., and Gregory A. Rowdon, M.D.
Summary: Pigmented villonodular synovitis involves proliferation of the synovium of joints, bursa, or tendon sheaths. It is a rare disorder that can occur in two forms. The diffuse form involves the entire synovium and occurs in the majority of cases. The localized form involves a discrete section of the synovium. The disorder almost always involves a singlejoint, and the knee is most commonly affected. The treatment of choice for the diffuse form is total synovectomy. Recurrence is common. The treatment of choice for the localized form is partial synovectomy. Recurrence is uncommon. We present a case report of a localized pigmented villonodular synovitis presenting as a locked lateral meniscal bucket handle tear in an otherwise healthy 27-year-old man. Key Words: Localized pigmented villonodular synovitis---Locked knee.
his knee, felt a " p o p " resulting in immediate relief of pain and the locking sensation. Over the next 48 h, the patient noted swelling and moderate discomfort of the knee. Approximately 1 week after his initial injury (and 1 week before his presentation), the patient again experienced a locking of his knee associated with a pop. The patient was ascending a ladder and carrying a compressor over his shoulder at the time. The patient felt a second pop and then noted resolution of the locking sensation. That evening, while attempting to stand from a seated position on the floor, the patient noted a third locking episode. With this episode, however, the patient was unable to get the knee unlocked. The next day, he saw his local physician who manipulated the patient's knee into greater extension, placed the patient into an immobilization brace for support, and referred the patient to our Sports Medicine Center. Examination of the knee at initial presentation showed a mechanical block to full extension and significant lateral joint line tenderness. A large joint effusion was present. Results of the patient's Lachman test, anterior and posterior drawer tests, and varus and valgus stress tests were normal. A four-
Pigmented villonodular synovitis is a disorder involving synovial proliferation of the joints, bursa, or tendon sheaths. It occurs in two forms: a diffuse disease involving the entire synovium or a discreet nodular mass involving only a small section of the synovium. The knee joint is most commonly affected. We present a case of localized pigmented villonodular synovitis of the knee presenting as a locked lateral meniscai bucket handle tear. CASE REPORT A 27-year-old man with no previous history of knee problems sustained a twisting injury to his right knee while working on a roof - 2 weeks before his presentation. The same day of the initial injury, the patient went to kneel, but felt his knee lock, preventing full extension. The patient had significant acute pain and, while attempting to straighten From the Methodist Sports Medicine Center, Indianapolis, Indiana, U.S.A. Address correspondence and reprint requests to Dr. Charles Van Meter, Methodist Sports Medicine Center, Department of Research and Education, 1815 North Capitol Avenue, Suite 401, Indianapolis, IN 46202, U.S.A.
309
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C. D. V A N METER A N D G. R O W D O N
view radiographic series of the knee was also normal. With varus stress and gentle manipulation, the locked knee was relieved, allowing the patient to fully extend his knee. The initial assessment was that of an unstable lateral meniscus bucket handle tear, and the patient accepted the recommendation of arthroscopy. Arthroscopy of the right knee was performed 1 day after the clinic visit. Arthroscopic findings were normal except for a small transverse posttraumatic appearing lesion of the articular cartilage of the medial femoral condyle (Fig. I) and a soft tissue mass of the synovium located behind the posterior horn of the lateral meniscus (Figs. 2 and 3). The medial femoral condyle lesion measured - 3 x 9 mm and had a small amount of surrounding chondromalacia. The soft tissue mass was a large pedunculated yellowish brown lesion attached to the synovium. There also was a free fragment of the mass lying in the posterior recess laterally. It was suspected that this fragment caused the lesion seen on the medial femoral condyle. The fragment was removed and sent for pathology evaluation~ and the mass attached to the synovium was resected. The synovium was debrided to a 1 cm margin from the lesion's stalk (Fig. 4). The synovial surfaces were meticulously inspected, and no other similar lesions or defects were found. All of the remaining joint surfaces and menisci were also without defects. The pathology report confirmed the intraoperative diagnosis of a focal pigmented villonodular synovitis (Figs. 5 and 6). The patient experienced no adverse events or complications from his arthroscopy. He was allowed to return home the same day as his procedure. He was begun on a rehabilitation program 5 days postoperatively. He was allowed to return to
FIG. L Medial femoral condyle lesion. Arthroscopy, Vol. 10, No. 3, 1994
FIG. 2. Localized pigmented viUonodular synovitis mass behind the posterior horn of the lateral meniscus.
work without restrictions and was released from follow-up 3 weeks postoperatively. He was symptom free. DISCUSSION Pigmented villonodular synovitis was first described by Jaffe et al. in 1941 (1). It is a rare disorder involving synovial proliferation of joints, bursa, or tendon sheaths. There has been one case report of a pigmented villonodular synovitis arising from a patellar plica (2). The estimated annual incidence rate is 1.8 cases per million (3). There is an equal sex distribution, and most cases occur in young adults, with a peak incidence in the third and fourth decades of life (age range 4-90 years; average 35) (3-6). The etiology of pigmented villonodular synovitis remains unclear. It was originally thought to be neo-
FIG. 3. Localized pigmented villonodular synovitis mass with probe showing severed end of lesion.
V I L L O N O D U L A R SYNOVITIS
311
FIG. 6. Pathology of localized pigmented villonodular synovitis demonstrating multinucleated giant cells and pigmentation.
FIG. 4. Partial synovectomy.
plastic, but is now thought by most investigators to be an inflammatory reaction to an unknown stimulus (1,6). However, other investigators attribute it to repeated trauma and/or hemarthrosis (3). Clinically, pigmented villonodular synovitis can behave as a locally aggressive benign neoplasm with invasion into surrounding soft tissue and/or bone. Pigmented villonodular synovitis exists in two distinct forms: a localized form, characterized by a discreet nodular or pedunculated lesion, and a diffuse form, involving the entire soft tissue lining. Beguin et al. (7) also reported a mixed form containing pedicled bulky tumors associated with diffuse synovitis. Pigmented villonodular synovitis is almost always monoarticular. The diffuse form occurs in approximately three fourths of all cases (3,8). The knee is the most commonly affected joint, also accounting for approximately three-fourths of total cases (3,8). Clinically, patients with the diffuse form of pigmented viUonodular synovitis present with an indo-
ii i!I
@i FIG. 5. Pathology of localized pigmented villonodular synovitis demonstrating hypercellularity.
lent course of increasing pain, joint swelling, and limitation of range of motion and/or stiffness. Occasionally, symptoms of locking, giving way, or a palpable mass accompany the above symptoms. The time between the onset of symptoms and presentation ranges from months to years. A review o f 99 cases (including both diffuse and localized forms) by Schwartz et al. (9) showed a mean duration of symptoms before presentation of 5 years (median 4 years; range 3.6 months to 30 years). An effusion, when present, commonly shows a bloody or dark brown aspirant, although it can also be normal in appearance. The synovial fluid has also been found to be high in cholesterol content. Radiographic findings in patients with the diffuse form of pigmented villonodular synovitis are variable. In a review of 25 cases in the knee by Flandry et al. (10), most findings were found to be in the soft tissue and consisted of soft tissue tumefactions and expansion of the suprapatellar synovial pouch. Bony changes were also present, although rarely, and consisted of cyst formation, cortical erosions, osteopenia, and mild degenerative changes. Other investigators have reported osseous changes in 1550% of patients for all joints, but the incidence of these findings depends on the size of the capsule involved (more frequent in the hip and less frequent in the knee) (3,6). Both computerized tomography (CT) and magnetic resonance imaging (MRI) are being used more frequently to aid in the diagnosis of pigmented viUonodular synovitis. The current treatment of choice for diffuse pigmented villonodular synovitis is synovectomy. Most investigators recommend total synovectomy, but, even with this procedure, there is a high rate of recurrence. Schwartz et al. (9) reported a recurArthroscopy, Vol. 10, No. 3, 1994
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rence rate of - 2 6 % at 25 years. Matsubara et al. (I 1) reported a recurrence rate in the knee of 35% at 8.1 years with a mean duration until recurrence of 2.3 years (range 1-5). Miller (12), on the other hand, recommended only subtotal synovectomy and reported a 0% recurrence rate in a series of 34 patients. However, neither the length of follow-up nor the form of pigmented villonodular synovitis were dearly presented in his series. Most patients undergo repeat synovectomy for recurrent disease. Wiss (13), however, advocated a radiation-induced synovectomy via intraarticular injection of yttrium90, a radiocolloid. There is a high complication rate (1%34%) reported after surgical synovectomy, consisting of joint pain and stiffness (8,9,11). Johansson et al. (8) recommended performing knee manipulation under general anesthesia 2 weeks after the total synovectomy procedure. Less information is available on the localized form of pigmented villonodular synovitis. Clinically, patients present with symptoms resembling acute mechanical derangement. Signs or symptoms include sudden onset of pain, swelling, limitation of motion, giving way episodes, palpable masses, and locking episodes. Radiographic findings tend to be absent. MRI evaluation, however, may become the test of choice in suspected cases. Treatment is partial synovectomy. Flandry et al. (14) reported the first partial synovectomy via the arthroscope. Localized pigmented villonodular synovitis has a good prognosis. There are only three reported series in which recurrent disease was found after local excision. Rao and Vigorita (4) had one recurrence in eight knees, Schwartz et al. (9) had two recurrences in 12 knees, and Byers et al. (15) had two recurrences in 13 knees. We report a case of localized pigmented villonodular synovitis of the knee presenting as a locked bucket handle tear of the lateral meniscus in a young, otherwise healthy 27-year-old man. The patient was treated via the arthroscope by partial synovectomy, and the intraoperative diagnosis was confirmed by pathology. The articular cartilage and menisci were totally without defects (except for one small transverse lesion of the articular cartilage of the medial femoral condyle) despite a clinical presentation identical to a locked bucket-handle tear of
Arthroscopy, Vol. 10, No. 3, 1994
the lateral meniscus. This case emphasizes the importance of maintaining the differential diagnosis while clinical problem solving. The differential diagnosis of a locked knee includes chronic loose body, acute osteochondral fragment, displaced meniscal tear, and a soft tissue mass (as in this case). The case also emphasizes the importance of a meticulous and thorough arthroscopic evaluation when the more commonly suspected causes of the signs or symptoms are not readily apparent. REFERENCES 1. Jaffe HL, Lichtenstein L, Sutro CJ. Pigmented villonodular synovitis, bursitis and tenosynovitis. Arch Pathol 1941;31: 731-65. 2. Mori Y, Hino H, Fujimoto A, Okumo H. Pigmented villonodular synovitis of patellar plica. Arthroscopy 1989;5:340-1. 3. Myers BW, Masi AT, Feigenbanm SL. Pigmented villonodular synovitis and tenosynovitis: a clinical epidemiologic study of 166 cases and literature review. Medicine 1980;59: 223-238. 4. Rao AS, Vigorita VJ. Pigmented villonodular synovitis (giant cell tumor of the tendon sheath and synovial membrane); a review of eighty-one cases. J Bone Joint Surg 1984;66:7694. 5. Spritzer CE, Dalinka MK, Kressel HY. Magnetic resonance imaging of pigmented viUonodular synovitis: a report of two cases. Skel Radiot 1987;16:316-9. 6. Docken WP. Pigmented villonodular synovitis: a review with illustrative case reports. Semin Arthritis Rheum 1979; 9:1-22. 7. Beguin J, Locker B, Vielpeau C, Souquieres G. Pigmented villonodular synovitis of the knee: results from 13 cases. Arthroscopy 1989;5:62-4. 8. Johansson JE, Ajjoub S, Coughlin LP, Wener JA, Cruess RL. Pigmented villonodular synovitis of joints. Clin Orthop 1982;163:159--66. 9. Schwartz HS, Unni KK, Pritchard DJ. Pigmented villonodular synovitis. A retrospective review of affected large joints. Clin Orthop 1989;247:243-55. 10. Flandry F, McCann SB, Hughston JC, Kurtz DM. Roentgenographic findings in pigmented villonodular synovitis of the knee. Clin Orthop 1989;247:208-19. 11. Matsubara T, Toyoda Y, Hirohata K. Long-term results of knee synovectomy in pigmented viUonodular synovitis. Todays OR Nurse 1992;14:19-29. 12. Miller WE. Villonodular synovitis: pigmented and nonpigmented variations. South Med J 1982;75:1084-6. 13. Wiss DA. Recurrent villonodular synovitis of the knee-successful treatment with yttrium-90. Clin Orthop 1982;169: 139--44. 14. Flandry FC, Jacobson KE, Andrews JR. Localized pigmented villonodular synovitis of the knee mimicking meniscat injury. Arthroscopy 1986;2:217-21. 15. Byers PD, Cotton RE, Deacon OW, et al. The diagnosis and treatment of pigmented villonodular synovitis~.J Bone Joint Surg[Br] 1968;50:290-305.
Case Report
Localized Pigmented Villonodular Synovitis Presenting as a Locked Lateral Meniscal Bucket Handle Tear: A Case Report and Review of the Literature Charles D. Van Meter, M.D., and Gregory A. Rowdon, M.D.
Summary: Pigmented villonodular synovitis involves proliferation of the synovium of joints, bursa, or tendon sheaths. It is a rare disorder that can occur in two forms. The diffuse form involves the entire synovium and occurs in the majority of cases. The localized form involves a discrete section of the synovium. The disorder almost always involves a singlejoint, and the knee is most commonly affected. The treatment of choice for the diffuse form is total synovectomy. Recurrence is common. The treatment of choice for the localized form is partial synovectomy. Recurrence is uncommon. We present a case report of a localized pigmented villonodular synovitis presenting as a locked lateral meniscal bucket handle tear in an otherwise healthy 27-year-old man. Key Words: Localized pigmented villonodular synovitis---Locked knee.
his knee, felt a " p o p " resulting in immediate relief of pain and the locking sensation. Over the next 48 h, the patient noted swelling and moderate discomfort of the knee. Approximately 1 week after his initial injury (and 1 week before his presentation), the patient again experienced a locking of his knee associated with a pop. The patient was ascending a ladder and carrying a compressor over his shoulder at the time. The patient felt a second pop and then noted resolution of the locking sensation. That evening, while attempting to stand from a seated position on the floor, the patient noted a third locking episode. With this episode, however, the patient was unable to get the knee unlocked. The next day, he saw his local physician who manipulated the patient's knee into greater extension, placed the patient into an immobilization brace for support, and referred the patient to our Sports Medicine Center. Examination of the knee at initial presentation showed a mechanical block to full extension and significant lateral joint line tenderness. A large joint effusion was present. Results of the patient's Lachman test, anterior and posterior drawer tests, and varus and valgus stress tests were normal. A four-
Pigmented villonodular synovitis is a disorder involving synovial proliferation of the joints, bursa, or tendon sheaths. It occurs in two forms: a diffuse disease involving the entire synovium or a discreet nodular mass involving only a small section of the synovium. The knee joint is most commonly affected. We present a case of localized pigmented villonodular synovitis of the knee presenting as a locked lateral meniscai bucket handle tear. CASE REPORT A 27-year-old man with no previous history of knee problems sustained a twisting injury to his right knee while working on a roof - 2 weeks before his presentation. The same day of the initial injury, the patient went to kneel, but felt his knee lock, preventing full extension. The patient had significant acute pain and, while attempting to straighten From the Methodist Sports Medicine Center, Indianapolis, Indiana, U.S.A. Address correspondence and reprint requests to Dr. Charles Van Meter, Methodist Sports Medicine Center, Department of Research and Education, 1815 North Capitol Avenue, Suite 401, Indianapolis, IN 46202, U.S.A.
309
310
C. D. V A N METER A N D G. R O W D O N
view radiographic series of the knee was also normal. With varus stress and gentle manipulation, the locked knee was relieved, allowing the patient to fully extend his knee. The initial assessment was that of an unstable lateral meniscus bucket handle tear, and the patient accepted the recommendation of arthroscopy. Arthroscopy of the right knee was performed 1 day after the clinic visit. Arthroscopic findings were normal except for a small transverse posttraumatic appearing lesion of the articular cartilage of the medial femoral condyle (Fig. I) and a soft tissue mass of the synovium located behind the posterior horn of the lateral meniscus (Figs. 2 and 3). The medial femoral condyle lesion measured - 3 x 9 mm and had a small amount of surrounding chondromalacia. The soft tissue mass was a large pedunculated yellowish brown lesion attached to the synovium. There also was a free fragment of the mass lying in the posterior recess laterally. It was suspected that this fragment caused the lesion seen on the medial femoral condyle. The fragment was removed and sent for pathology evaluation~ and the mass attached to the synovium was resected. The synovium was debrided to a 1 cm margin from the lesion's stalk (Fig. 4). The synovial surfaces were meticulously inspected, and no other similar lesions or defects were found. All of the remaining joint surfaces and menisci were also without defects. The pathology report confirmed the intraoperative diagnosis of a focal pigmented villonodular synovitis (Figs. 5 and 6). The patient experienced no adverse events or complications from his arthroscopy. He was allowed to return home the same day as his procedure. He was begun on a rehabilitation program 5 days postoperatively. He was allowed to return to
FIG. L Medial femoral condyle lesion. Arthroscopy, Vol. 10, No. 3, 1994
FIG. 2. Localized pigmented viUonodular synovitis mass behind the posterior horn of the lateral meniscus.
work without restrictions and was released from follow-up 3 weeks postoperatively. He was symptom free. DISCUSSION Pigmented villonodular synovitis was first described by Jaffe et al. in 1941 (1). It is a rare disorder involving synovial proliferation of joints, bursa, or tendon sheaths. There has been one case report of a pigmented villonodular synovitis arising from a patellar plica (2). The estimated annual incidence rate is 1.8 cases per million (3). There is an equal sex distribution, and most cases occur in young adults, with a peak incidence in the third and fourth decades of life (age range 4-90 years; average 35) (3-6). The etiology of pigmented villonodular synovitis remains unclear. It was originally thought to be neo-
FIG. 3. Localized pigmented villonodular synovitis mass with probe showing severed end of lesion.
V I L L O N O D U L A R SYNOVITIS
311
FIG. 6. Pathology of localized pigmented villonodular synovitis demonstrating multinucleated giant cells and pigmentation.
FIG. 4. Partial synovectomy.
plastic, but is now thought by most investigators to be an inflammatory reaction to an unknown stimulus (1,6). However, other investigators attribute it to repeated trauma and/or hemarthrosis (3). Clinically, pigmented villonodular synovitis can behave as a locally aggressive benign neoplasm with invasion into surrounding soft tissue and/or bone. Pigmented villonodular synovitis exists in two distinct forms: a localized form, characterized by a discreet nodular or pedunculated lesion, and a diffuse form, involving the entire soft tissue lining. Beguin et al. (7) also reported a mixed form containing pedicled bulky tumors associated with diffuse synovitis. Pigmented villonodular synovitis is almost always monoarticular. The diffuse form occurs in approximately three fourths of all cases (3,8). The knee is the most commonly affected joint, also accounting for approximately three-fourths of total cases (3,8). Clinically, patients with the diffuse form of pigmented viUonodular synovitis present with an indo-
ii i!I
@i FIG. 5. Pathology of localized pigmented villonodular synovitis demonstrating hypercellularity.
lent course of increasing pain, joint swelling, and limitation of range of motion and/or stiffness. Occasionally, symptoms of locking, giving way, or a palpable mass accompany the above symptoms. The time between the onset of symptoms and presentation ranges from months to years. A review o f 99 cases (including both diffuse and localized forms) by Schwartz et al. (9) showed a mean duration of symptoms before presentation of 5 years (median 4 years; range 3.6 months to 30 years). An effusion, when present, commonly shows a bloody or dark brown aspirant, although it can also be normal in appearance. The synovial fluid has also been found to be high in cholesterol content. Radiographic findings in patients with the diffuse form of pigmented villonodular synovitis are variable. In a review of 25 cases in the knee by Flandry et al. (10), most findings were found to be in the soft tissue and consisted of soft tissue tumefactions and expansion of the suprapatellar synovial pouch. Bony changes were also present, although rarely, and consisted of cyst formation, cortical erosions, osteopenia, and mild degenerative changes. Other investigators have reported osseous changes in 1550% of patients for all joints, but the incidence of these findings depends on the size of the capsule involved (more frequent in the hip and less frequent in the knee) (3,6). Both computerized tomography (CT) and magnetic resonance imaging (MRI) are being used more frequently to aid in the diagnosis of pigmented viUonodular synovitis. The current treatment of choice for diffuse pigmented villonodular synovitis is synovectomy. Most investigators recommend total synovectomy, but, even with this procedure, there is a high rate of recurrence. Schwartz et al. (9) reported a recurArthroscopy, Vol. 10, No. 3, 1994
312
C. D. V A N METER A N D G. ROWDON
rence rate of - 2 6 % at 25 years. Matsubara et al. (I 1) reported a recurrence rate in the knee of 35% at 8.1 years with a mean duration until recurrence of 2.3 years (range 1-5). Miller (12), on the other hand, recommended only subtotal synovectomy and reported a 0% recurrence rate in a series of 34 patients. However, neither the length of follow-up nor the form of pigmented villonodular synovitis were dearly presented in his series. Most patients undergo repeat synovectomy for recurrent disease. Wiss (13), however, advocated a radiation-induced synovectomy via intraarticular injection of yttrium90, a radiocolloid. There is a high complication rate (1%34%) reported after surgical synovectomy, consisting of joint pain and stiffness (8,9,11). Johansson et al. (8) recommended performing knee manipulation under general anesthesia 2 weeks after the total synovectomy procedure. Less information is available on the localized form of pigmented villonodular synovitis. Clinically, patients present with symptoms resembling acute mechanical derangement. Signs or symptoms include sudden onset of pain, swelling, limitation of motion, giving way episodes, palpable masses, and locking episodes. Radiographic findings tend to be absent. MRI evaluation, however, may become the test of choice in suspected cases. Treatment is partial synovectomy. Flandry et al. (14) reported the first partial synovectomy via the arthroscope. Localized pigmented villonodular synovitis has a good prognosis. There are only three reported series in which recurrent disease was found after local excision. Rao and Vigorita (4) had one recurrence in eight knees, Schwartz et al. (9) had two recurrences in 12 knees, and Byers et al. (15) had two recurrences in 13 knees. We report a case of localized pigmented villonodular synovitis of the knee presenting as a locked bucket handle tear of the lateral meniscus in a young, otherwise healthy 27-year-old man. The patient was treated via the arthroscope by partial synovectomy, and the intraoperative diagnosis was confirmed by pathology. The articular cartilage and menisci were totally without defects (except for one small transverse lesion of the articular cartilage of the medial femoral condyle) despite a clinical presentation identical to a locked bucket-handle tear of
Arthroscopy, Vol. 10, No. 3, 1994
the lateral meniscus. This case emphasizes the importance of maintaining the differential diagnosis while clinical problem solving. The differential diagnosis of a locked knee includes chronic loose body, acute osteochondral fragment, displaced meniscal tear, and a soft tissue mass (as in this case). The case also emphasizes the importance of a meticulous and thorough arthroscopic evaluation when the more commonly suspected causes of the signs or symptoms are not readily apparent. REFERENCES 1. Jaffe HL, Lichtenstein L, Sutro CJ. Pigmented villonodular synovitis, bursitis and tenosynovitis. Arch Pathol 1941;31: 731-65. 2. Mori Y, Hino H, Fujimoto A, Okumo H. Pigmented villonodular synovitis of patellar plica. Arthroscopy 1989;5:340-1. 3. Myers BW, Masi AT, Feigenbanm SL. Pigmented villonodular synovitis and tenosynovitis: a clinical epidemiologic study of 166 cases and literature review. Medicine 1980;59: 223-238. 4. Rao AS, Vigorita VJ. Pigmented villonodular synovitis (giant cell tumor of the tendon sheath and synovial membrane); a review of eighty-one cases. J Bone Joint Surg 1984;66:7694. 5. Spritzer CE, Dalinka MK, Kressel HY. Magnetic resonance imaging of pigmented viUonodular synovitis: a report of two cases. Skel Radiot 1987;16:316-9. 6. Docken WP. Pigmented villonodular synovitis: a review with illustrative case reports. Semin Arthritis Rheum 1979; 9:1-22. 7. Beguin J, Locker B, Vielpeau C, Souquieres G. Pigmented villonodular synovitis of the knee: results from 13 cases. Arthroscopy 1989;5:62-4. 8. Johansson JE, Ajjoub S, Coughlin LP, Wener JA, Cruess RL. Pigmented villonodular synovitis of joints. Clin Orthop 1982;163:159--66. 9. Schwartz HS, Unni KK, Pritchard DJ. Pigmented villonodular synovitis. A retrospective review of affected large joints. Clin Orthop 1989;247:243-55. 10. Flandry F, McCann SB, Hughston JC, Kurtz DM. Roentgenographic findings in pigmented villonodular synovitis of the knee. Clin Orthop 1989;247:208-19. 11. Matsubara T, Toyoda Y, Hirohata K. Long-term results of knee synovectomy in pigmented viUonodular synovitis. Todays OR Nurse 1992;14:19-29. 12. Miller WE. Villonodular synovitis: pigmented and nonpigmented variations. South Med J 1982;75:1084-6. 13. Wiss DA. Recurrent villonodular synovitis of the knee-successful treatment with yttrium-90. Clin Orthop 1982;169: 139--44. 14. Flandry FC, Jacobson KE, Andrews JR. Localized pigmented villonodular synovitis of the knee mimicking meniscat injury. Arthroscopy 1986;2:217-21. 15. Byers PD, Cotton RE, Deacon OW, et al. The diagnosis and treatment of pigmented villonodular synovitis~.J Bone Joint Surg[Br] 1968;50:290-305.