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Imaging of Intraarticular Masses¹

¹ From the Department of Radiology, University of Southern California Keck School of Medicine, 1200 N State St, Suite 3550, Los Angeles, CA 90033. Presented as an education exhibit at the 2003 RSNA Scientific Assembly. Received March 23, 2004; revision requested April 27 and received June 1; accepted June 1. All authors have no financial relationships to disclose. Address correspondence to P.J.S. (e-mail: psheldon@usc.edu).

View larger version (132K): [in this window] [in a new window] [Download PPT slide]   Figure 1a.  (a) Arthrogram of the right shoulder in a patient with calcific bursitis reveals a calcified nodule in the subdeltoid bursa (white arrowhead). Note the normal extension of contrast material into the axillary recess (black arrowhead), into the subscapular bursa (black arrow), and along the tendon sheath of the long head of the biceps brachii muscle (white arrow). (b) Anteroposterior radiograph of the right shoulder in a different patient with synovial osteochondromatosis shows the characteristic calcified nodules. Understanding of the normal joint anatomy is essential to realize that the calcified nodules are intraarticular in the axillary recess (arrowhead), in the subscapular bursa (black arrow), and extending along the biceps tendon sheath (white arrow).

View larger version (113K): [in this window] [in a new window] [Download PPT slide]   Figure 1b.  (a) Arthrogram of the right shoulder in a patient with calcific bursitis reveals a calcified nodule in the subdeltoid bursa (white arrowhead). Note the normal extension of contrast material into the axillary recess (black arrowhead), into the subscapular bursa (black arrow), and along the tendon sheath of the long head of the biceps brachii muscle (white arrow). (b) Anteroposterior radiograph of the right shoulder in a different patient with synovial osteochondromatosis shows the characteristic calcified nodules. Understanding of the normal joint anatomy is essential to realize that the calcified nodules are intraarticular in the axillary recess (arrowhead), in the subscapular bursa (black arrow), and extending along the biceps tendon sheath (white arrow).

View larger version (152K): [in this window] [in a new window] [Download PPT slide]   Figure 2a.  Synovial osteochondromatosis of the right knee in a 42-year-old patient. (a) Lateral radiograph shows multiple calcified nodules (arrow) anterior to the proximal tibia. (b) Sagittal proton density-weighted MR image demonstrates that these low-signal-intensity calcified nodules (arrow) are located in the deep infrapatellar bursa.

View larger version (173K): [in this window] [in a new window] [Download PPT slide]   Figure 2b.  Synovial osteochondromatosis of the right knee in a 42-year-old patient. (a) Lateral radiograph shows multiple calcified nodules (arrow) anterior to the proximal tibia. (b) Sagittal proton density-weighted MR image demonstrates that these low-signal-intensity calcified nodules (arrow) are located in the deep infrapatellar bursa.

View larger version (131K): [in this window] [in a new window] [Download PPT slide]   Figure 3a.  Coronal (a) and axial (b) short inversion time inversion-recovery (STIR) images demonstrate bilateral hip joint effusions, with the left effusion being larger than the right. The left hip effusion fills a distended left iliopsoas bursa (*), and the small right hip joint effusion extends into the right iliopsoas bursa (arrow).

View larger version (130K): [in this window] [in a new window] [Download PPT slide]   Figure 3b.  Coronal (a) and axial (b) short inversion time inversion-recovery (STIR) images demonstrate bilateral hip joint effusions, with the left effusion being larger than the right. The left hip effusion fills a distended left iliopsoas bursa (*), and the small right hip joint effusion extends into the right iliopsoas bursa (arrow).

View larger version (95K): [in this window] [in a new window] [Download PPT slide]   Figure 4a.  Septic arthritis of the ankle joint. (a) Anteroposterior arthrogram demonstrates contrast material extending up the calf (arrow). Note the sinus track exiting out to the skin laterally (arrowhead). (b) Sagittal STIR MR image demonstrates fluid extending up from the ankle joint into the flexor hallicus longus tendon sheath (arrow).

View larger version (114K): [in this window] [in a new window] [Download PPT slide]   Figure 4b.  Septic arthritis of the ankle joint. (a) Anteroposterior arthrogram demonstrates contrast material extending up the calf (arrow). Note the sinus track exiting out to the skin laterally (arrowhead). (b) Sagittal STIR MR image demonstrates fluid extending up from the ankle joint into the flexor hallicus longus tendon sheath (arrow).

View larger version (144K): [in this window] [in a new window] [Download PPT slide]   Figure 5a.  Lipoma arborescens in a 50-year-old man with knee swelling. (a) Lateral radiograph of the knee reveals fullness of the suprapatellar bursa with radiolucent areas (arrow) suggestive of fat. (b) Sagittal proton density-weighted MR image shows a lobulated mass in the suprapatellar bursa (arrow) with signal intensity equivalent to that of fat. (c) Sagittal proton density-weighted MR image with fat saturation shows loss of signal of the synovial proliferation (arrow) surrounded by a large joint effusion extending into the popliteal bursa (*). (d) Long-axis ultrasound (US) image shows distention of the suprapatellar bursa by a mass with characteristic frondlike projections (arrows) surrounded by a joint effusion (*).

View larger version (184K): [in this window] [in a new window] [Download PPT slide]   Figure 5b.  Lipoma arborescens in a 50-year-old man with knee swelling. (a) Lateral radiograph of the knee reveals fullness of the suprapatellar bursa with radiolucent areas (arrow) suggestive of fat. (b) Sagittal proton density-weighted MR image shows a lobulated mass in the suprapatellar bursa (arrow) with signal intensity equivalent to that of fat. (c) Sagittal proton density-weighted MR image with fat saturation shows loss of signal of the synovial proliferation (arrow) surrounded by a large joint effusion extending into the popliteal bursa (*). (d) Long-axis ultrasound (US) image shows distention of the suprapatellar bursa by a mass with characteristic frondlike projections (arrows) surrounded by a joint effusion (*).

View larger version (161K): [in this window] [in a new window] [Download PPT slide]   Figure 5c.  Lipoma arborescens in a 50-year-old man with knee swelling. (a) Lateral radiograph of the knee reveals fullness of the suprapatellar bursa with radiolucent areas (arrow) suggestive of fat. (b) Sagittal proton density-weighted MR image shows a lobulated mass in the suprapatellar bursa (arrow) with signal intensity equivalent to that of fat. (c) Sagittal proton density-weighted MR image with fat saturation shows loss of signal of the synovial proliferation (arrow) surrounded by a large joint effusion extending into the popliteal bursa (*). (d) Long-axis ultrasound (US) image shows distention of the suprapatellar bursa by a mass with characteristic frondlike projections (arrows) surrounded by a joint effusion (*).

View larger version (161K): [in this window] [in a new window] [Download PPT slide]   Figure 5d.  Lipoma arborescens in a 50-year-old man with knee swelling. (a) Lateral radiograph of the knee reveals fullness of the suprapatellar bursa with radiolucent areas (arrow) suggestive of fat. (b) Sagittal proton density-weighted MR image shows a lobulated mass in the suprapatellar bursa (arrow) with signal intensity equivalent to that of fat. (c) Sagittal proton density-weighted MR image with fat saturation shows loss of signal of the synovial proliferation (arrow) surrounded by a large joint effusion extending into the popliteal bursa (*). (d) Long-axis ultrasound (US) image shows distention of the suprapatellar bursa by a mass with characteristic frondlike projections (arrows) surrounded by a joint effusion (*).

View larger version (153K): [in this window] [in a new window] [Download PPT slide]   Figure 6a.  Synovial osteochondromatosis of the wrist. (a) Anteroposterior radiograph of the wrist demonstrates multiple small, calcified nodules (white arrows) of characteristically uniform size in the radioulnar joint. Note the erosive changes (black arrows) of the distal radius and ulna. (b) Coronal proton density-weighted MR image demonstrates an intermediate-signal-intensity mass (*) in the radioulnar joint. (c) Coronal T2-weighted image shows that the mass (*) is hyperintense. On both MR images, note the multiple low-signal-intensity areas (arrowhead), which correspond to areas of calcification seen on the radiograph.

View larger version (165K): [in this window] [in a new window] [Download PPT slide]   Figure 6b.  Synovial osteochondromatosis of the wrist. (a) Anteroposterior radiograph of the wrist demonstrates multiple small, calcified nodules (white arrows) of characteristically uniform size in the radioulnar joint. Note the erosive changes (black arrows) of the distal radius and ulna. (b) Coronal proton density-weighted MR image demonstrates an intermediate-signal-intensity mass (*) in the radioulnar joint. (c) Coronal T2-weighted image shows that the mass (*) is hyperintense. On both MR images, note the multiple low-signal-intensity areas (arrowhead), which correspond to areas of calcification seen on the radiograph.

View larger version (177K): [in this window] [in a new window] [Download PPT slide]   Figure 6c.  Synovial osteochondromatosis of the wrist. (a) Anteroposterior radiograph of the wrist demonstrates multiple small, calcified nodules (white arrows) of characteristically uniform size in the radioulnar joint. Note the erosive changes (black arrows) of the distal radius and ulna. (b) Coronal proton density-weighted MR image demonstrates an intermediate-signal-intensity mass (*) in the radioulnar joint. (c) Coronal T2-weighted image shows that the mass (*) is hyperintense. On both MR images, note the multiple low-signal-intensity areas (arrowhead), which correspond to areas of calcification seen on the radiograph.

View larger version (183K): [in this window] [in a new window] [Download PPT slide]   Figure 7a.  Diffuse PVNS of the knee in a 43-year-old woman. (a) Sagittal proton density-weighted MR image shows lobulated, masslike synovial proliferation with characteristic low signal intensity. Note the tibial articular erosions. (b) Corresponding coronal T2-weighted MR images through the anterior right knee demonstrate massive distention of the suprapatellar pouch by lobulated proliferative synovium with characteristic low signal intensity because of hemosiderin deposition.

View larger version (179K): [in this window] [in a new window] [Download PPT slide]   Figure 7b.  Diffuse PVNS of the knee in a 43-year-old woman. (a) Sagittal proton density-weighted MR image shows lobulated, masslike synovial proliferation with characteristic low signal intensity. Note the tibial articular erosions. (b) Corresponding coronal T2-weighted MR images through the anterior right knee demonstrate massive distention of the suprapatellar pouch by lobulated proliferative synovium with characteristic low signal intensity because of hemosiderin deposition.

View larger version (160K): [in this window] [in a new window] [Download PPT slide]   Figure 8a.  Focal PVNS of the knee in a 47-year-old woman. (a) Sagittal proton density-weighted MR image demonstrates a low-signal-intensity mass (arrow) in the anterior joint space. (b) Sagittal T2-weighted MR image shows the mass (arrow) with characteristic persistent low signal intensity.

View larger version (169K): [in this window] [in a new window] [Download PPT slide]   Figure 8b.  Focal PVNS of the knee in a 47-year-old woman. (a) Sagittal proton density-weighted MR image demonstrates a low-signal-intensity mass (arrow) in the anterior joint space. (b) Sagittal T2-weighted MR image shows the mass (arrow) with characteristic persistent low signal intensity.

View larger version (149K): [in this window] [in a new window] [Download PPT slide]   Figure 9a.  Rheumatoid arthritis of the ankle in a 61-year-old woman. (a) Anteroposterior radiograph of the ankle demonstrates a large lytic lesion in the talus (arrow). The lesion was initially thought to be a bone tumor, but the erosions of the fibula (arrowheads) indicate that the primary disease is in the joint. (b) Sagittal T1-weighted MR image demonstrates a low-signal-intensity lesion (*) in the talus with low-signal-intensity pannus (arrows) in the joint space. (c) Sagittal STIR MR image demonstrates intermediate-signal-intensity pannus (arrows) and high signal intensity in the talus representing a large subchondral geode (*).

View larger version (165K): [in this window] [in a new window] [Download PPT slide]   Figure 9b.  Rheumatoid arthritis of the ankle in a 61-year-old woman. (a) Anteroposterior radiograph of the ankle demonstrates a large lytic lesion in the talus (arrow). The lesion was initially thought to be a bone tumor, but the erosions of the fibula (arrowheads) indicate that the primary disease is in the joint. (b) Sagittal T1-weighted MR image demonstrates a low-signal-intensity lesion (*) in the talus with low-signal-intensity pannus (arrows) in the joint space. (c) Sagittal STIR MR image demonstrates intermediate-signal-intensity pannus (arrows) and high signal intensity in the talus representing a large subchondral geode (*).

View larger version (155K): [in this window] [in a new window] [Download PPT slide]   Figure 9c.  Rheumatoid arthritis of the ankle in a 61-year-old woman. (a) Anteroposterior radiograph of the ankle demonstrates a large lytic lesion in the talus (arrow). The lesion was initially thought to be a bone tumor, but the erosions of the fibula (arrowheads) indicate that the primary disease is in the joint. (b) Sagittal T1-weighted MR image demonstrates a low-signal-intensity lesion (*) in the talus with low-signal-intensity pannus (arrows) in the joint space. (c) Sagittal STIR MR image demonstrates intermediate-signal-intensity pannus (arrows) and high signal intensity in the talus representing a large subchondral geode (*).

View larger version (156K): [in this window] [in a new window] [Download PPT slide]   Figure 10a.  Tuberculous arthritis of the right shoulder in a patient with clinically suspected sarcoma because of a large rock-hard mass in the shoulder. (a, b) Coronal T1-weighted MR image (a) and T2-weighted image with fat saturation (b) of the right shoulder demonstrate a humeral head erosion (arrowhead) and a distended joint space with proliferative synovium (arrow). Note the adjacent large mass (*). (c) Coronal postcontrast T1-weighted MR image with fat saturation demonstrates that the mass (*) is a fluid-filled collection with an enhancing periphery rather than a solid tumor. Note the enhancement of the synovium within the joint (arrow) and the marginal erosion (arrowhead). The combination of a destructive inflammatory arthritis decompressing into the adjacent subdeltoid bursa to form a cold abscess is typical of tuberculous arthritis.

View larger version (146K): [in this window] [in a new window] [Download PPT slide]   Figure 10b.  Tuberculous arthritis of the right shoulder in a patient with clinically suspected sarcoma because of a large rock-hard mass in the shoulder. (a, b) Coronal T1-weighted MR image (a) and T2-weighted image with fat saturation (b) of the right shoulder demonstrate a humeral head erosion (arrowhead) and a distended joint space with proliferative synovium (arrow). Note the adjacent large mass (*). (c) Coronal postcontrast T1-weighted MR image with fat saturation demonstrates that the mass (*) is a fluid-filled collection with an enhancing periphery rather than a solid tumor. Note the enhancement of the synovium within the joint (arrow) and the marginal erosion (arrowhead). The combination of a destructive inflammatory arthritis decompressing into the adjacent subdeltoid bursa to form a cold abscess is typical of tuberculous arthritis.

View larger version (144K): [in this window] [in a new window] [Download PPT slide]   Figure 10c.  Tuberculous arthritis of the right shoulder in a patient with clinically suspected sarcoma because of a large rock-hard mass in the shoulder. (a, b) Coronal T1-weighted MR image (a) and T2-weighted image with fat saturation (b) of the right shoulder demonstrate a humeral head erosion (arrowhead) and a distended joint space with proliferative synovium (arrow). Note the adjacent large mass (*). (c) Coronal postcontrast T1-weighted MR image with fat saturation demonstrates that the mass (*) is a fluid-filled collection with an enhancing periphery rather than a solid tumor. Note the enhancement of the synovium within the joint (arrow) and the marginal erosion (arrowhead). The combination of a destructive inflammatory arthritis decompressing into the adjacent subdeltoid bursa to form a cold abscess is typical of tuberculous arthritis.

View larger version (149K): [in this window] [in a new window] [Download PPT slide]   Figure 11a.  Coccidioidomycosis arthritis of the knee. (a, b) Coronal T1-weighted MR image (a) and proton density-weighted MR image with fat saturation (b) demonstrate a joint effusion and marginal erosions of the proximal tibia with preservation of the joint spaces. (c) Axial proton density-weighted MR image with fat saturation demonstrates multiple rice bodies (arrow) within a joint effusion.

View larger version (165K): [in this window] [in a new window] [Download PPT slide]   Figure 11b.  Coccidioidomycosis arthritis of the knee. (a, b) Coronal T1-weighted MR image (a) and proton density-weighted MR image with fat saturation (b) demonstrate a joint effusion and marginal erosions of the proximal tibia with preservation of the joint spaces. (c) Axial proton density-weighted MR image with fat saturation demonstrates multiple rice bodies (arrow) within a joint effusion.

View larger version (161K): [in this window] [in a new window] [Download PPT slide]   Figure 11c.  Coccidioidomycosis arthritis of the knee. (a, b) Coronal T1-weighted MR image (a) and proton density-weighted MR image with fat saturation (b) demonstrate a joint effusion and marginal erosions of the proximal tibia with preservation of the joint spaces. (c) Axial proton density-weighted MR image with fat saturation demonstrates multiple rice bodies (arrow) within a joint effusion.

View larger version (109K): [in this window] [in a new window] [Download PPT slide]   Figure 12a.  Gout in a 48-year-old man with suspected osteomyelitis of the first toe. (a) Sagittal T1-weighted MR image of the first toe demonstrates an erosion with an overhanging edge (arrow) at the distal metatarsal head, preserved joint space, and a periarticular intermediate-signal-intensity gouty tophus (*). (b) Sagittal STIR MR image demonstrates low signal intensity of the gouty tophus (*).

View larger version (116K): [in this window] [in a new window] [Download PPT slide]   Figure 12b.  Gout in a 48-year-old man with suspected osteomyelitis of the first toe. (a) Sagittal T1-weighted MR image of the first toe demonstrates an erosion with an overhanging edge (arrow) at the distal metatarsal head, preserved joint space, and a periarticular intermediate-signal-intensity gouty tophus (*). (b) Sagittal STIR MR image demonstrates low signal intensity of the gouty tophus (*).

View larger version (24K): [in this window] [in a new window] [Download PPT slide]   Figure 13a.  Amyloid arthropathy in a 70-year-old woman with a 15-year history of dialysis. (a) Anteroposterior radiograph of the knee demonstrates a lytic lesion of the medial posterior tibia (arrow). (b) Sagittal T1-weighted MR image reveals distention of the joint space and popliteal cyst (*) by intermediate-signal-intensity material with a pressure erosion of the posterior tibia (arrow). (c) Sagittal T2-weighted MR image demonstrates fluid as well as low-signal-intensity amyloid deposits filling the joint space and popliteal cyst. (Case reprinted, with permission, from reference 28.)

View larger version (24K): [in this window] [in a new window] [Download PPT slide]   Figure 13b.  Amyloid arthropathy in a 70-year-old woman with a 15-year history of dialysis. (a) Anteroposterior radiograph of the knee demonstrates a lytic lesion of the medial posterior tibia (arrow). (b) Sagittal T1-weighted MR image reveals distention of the joint space and popliteal cyst (*) by intermediate-signal-intensity material with a pressure erosion of the posterior tibia (arrow). (c) Sagittal T2-weighted MR image demonstrates fluid as well as low-signal-intensity amyloid deposits filling the joint space and popliteal cyst. (Case reprinted, with permission, from reference 28.)

View larger version (24K): [in this window] [in a new window] [Download PPT slide]   Figure 13c.  Amyloid arthropathy in a 70-year-old woman with a 15-year history of dialysis. (a) Anteroposterior radiograph of the knee demonstrates a lytic lesion of the medial posterior tibia (arrow). (b) Sagittal T1-weighted MR image reveals distention of the joint space and popliteal cyst (*) by intermediate-signal-intensity material with a pressure erosion of the posterior tibia (arrow). (c) Sagittal T2-weighted MR image demonstrates fluid as well as low-signal-intensity amyloid deposits filling the joint space and popliteal cyst. (Case reprinted, with permission, from reference 28.)

View larger version (176K): [in this window] [in a new window] [Download PPT slide]   Figure 14a.  Synovial hemangioma in a 21-year-old woman who complained of a mass above her knee. (a) Sagittal proton density-weighted MR image of the knee shows an intermediate-signal-intensity mass (arrow) in the suprapatellar bursa that invades the musculature anteriorly. (b) Sagittal proton density-weighted MR image with fat saturation demonstrates the markedly high signal intensity of this synovial hemangioma, a finding that reflects pooling of blood within vascular spaces. (c) Axial proton density-weighted MR image with fat saturation demonstrates the high-signal-intensity mass in the suprapatellar bursa that extends anteriorly into the vastus medialis muscle (arrow).

View larger version (168K): [in this window] [in a new window] [Download PPT slide]   Figure 14b.  Synovial hemangioma in a 21-year-old woman who complained of a mass above her knee. (a) Sagittal proton density-weighted MR image of the knee shows an intermediate-signal-intensity mass (arrow) in the suprapatellar bursa that invades the musculature anteriorly. (b) Sagittal proton density-weighted MR image with fat saturation demonstrates the markedly high signal intensity of this synovial hemangioma, a finding that reflects pooling of blood within vascular spaces. (c) Axial proton density-weighted MR image with fat saturation demonstrates the high-signal-intensity mass in the suprapatellar bursa that extends anteriorly into the vastus medialis muscle (arrow).

View larger version (170K): [in this window] [in a new window] [Download PPT slide]   Figure 14c.  Synovial hemangioma in a 21-year-old woman who complained of a mass above her knee. (a) Sagittal proton density-weighted MR image of the knee shows an intermediate-signal-intensity mass (arrow) in the suprapatellar bursa that invades the musculature anteriorly. (b) Sagittal proton density-weighted MR image with fat saturation demonstrates the markedly high signal intensity of this synovial hemangioma, a finding that reflects pooling of blood within vascular spaces. (c) Axial proton density-weighted MR image with fat saturation demonstrates the high-signal-intensity mass in the suprapatellar bursa that extends anteriorly into the vastus medialis muscle (arrow).

View larger version (121K): [in this window] [in a new window] [Download PPT slide]   Figure 15a.  Klippel-Trénaunay-Weber syndrome in a 25-year-old man. (a) Photograph shows a nevus flammeus (arrow) of the left lower extremity. Note the overgrowth of the left leg and foot. (b, c) Axial T1-weighted (b) and T2-weighted (c) MR images demonstrate a joint effusion (*) and an intermediate-signal-intensity AVM in the suprapatellar bursa with a prominent serpentine signal void (arrow) from a large feeding artery. Note the large superficial dilated veins (arrowheads).

View larger version (181K): [in this window] [in a new window] [Download PPT slide]   Figure 15b.  Klippel-Trénaunay-Weber syndrome in a 25-year-old man. (a) Photograph shows a nevus flammeus (arrow) of the left lower extremity. Note the overgrowth of the left leg and foot. (b, c) Axial T1-weighted (b) and T2-weighted (c) MR images demonstrate a joint effusion (*) and an intermediate-signal-intensity AVM in the suprapatellar bursa with a prominent serpentine signal void (arrow) from a large feeding artery. Note the large superficial dilated veins (arrowheads).

View larger version (172K): [in this window] [in a new window] [Download PPT slide]   Figure 15c.  Klippel-Trénaunay-Weber syndrome in a 25-year-old man. (a) Photograph shows a nevus flammeus (arrow) of the left lower extremity. Note the overgrowth of the left leg and foot. (b, c) Axial T1-weighted (b) and T2-weighted (c) MR images demonstrate a joint effusion (*) and an intermediate-signal-intensity AVM in the suprapatellar bursa with a prominent serpentine signal void (arrow) from a large feeding artery. Note the large superficial dilated veins (arrowheads).

View larger version (163K): [in this window] [in a new window] [Download PPT slide]   Figure 16a.  Synovial chondrosarcoma in a 52-year-old man with a swollen knee in whom synovial osteochondromatosis had been diagnosed at biopsy 10 years earlier. (a) Lateral radiograph of the knee demonstrates distention of the joint space by a soft-tissue mass that contains areas of calcified matrix (arrows). (b) Axial CT scan of the knee demonstrates a large soft-tissue mass (*) in the joint space. Note the erosions of the distal femoral condyles (arrows), which are less apparent on the conventional radiograph. (c) Axial T1-weighted MR image demonstrates a large lobulated low-signal-intensity mass (*) distending the joint space, with erosion and invasion of the femoral condyles (arrows). (d) Axial T2-weighted MR image obtained more distally demonstrates high signal intensity (*) within the mass. (e, f) Precontrast (e) and postcontrast (f) sagittal T1-weighted MR images of the knee demonstrate heterogeneous enhancement of the infiltrating intraarticular synovial chondrosarcoma (*).

View larger version (116K): [in this window] [in a new window] [Download PPT slide]   Figure 16b.  Synovial chondrosarcoma in a 52-year-old man with a swollen knee in whom synovial osteochondromatosis had been diagnosed at biopsy 10 years earlier. (a) Lateral radiograph of the knee demonstrates distention of the joint space by a soft-tissue mass that contains areas of calcified matrix (arrows). (b) Axial CT scan of the knee demonstrates a large soft-tissue mass (*) in the joint space. Note the erosions of the distal femoral condyles (arrows), which are less apparent on the conventional radiograph. (c) Axial T1-weighted MR image demonstrates a large lobulated low-signal-intensity mass (*) distending the joint space, with erosion and invasion of the femoral condyles (arrows). (d) Axial T2-weighted MR image obtained more distally demonstrates high signal intensity (*) within the mass. (e, f) Precontrast (e) and postcontrast (f) sagittal T1-weighted MR images of the knee demonstrate heterogeneous enhancement of the infiltrating intraarticular synovial chondrosarcoma (*).

View larger version (148K): [in this window] [in a new window] [Download PPT slide]   Figure 16c.  Synovial chondrosarcoma in a 52-year-old man with a swollen knee in whom synovial osteochondromatosis had been diagnosed at biopsy 10 years earlier. (a) Lateral radiograph of the knee demonstrates distention of the joint space by a soft-tissue mass that contains areas of calcified matrix (arrows). (b) Axial CT scan of the knee demonstrates a large soft-tissue mass (*) in the joint space. Note the erosions of the distal femoral condyles (arrows), which are less apparent on the conventional radiograph. (c) Axial T1-weighted MR image demonstrates a large lobulated low-signal-intensity mass (*) distending the joint space, with erosion and invasion of the femoral condyles (arrows). (d) Axial T2-weighted MR image obtained more distally demonstrates high signal intensity (*) within the mass. (e, f) Precontrast (e) and postcontrast (f) sagittal T1-weighted MR images of the knee demonstrate heterogeneous enhancement of the infiltrating intraarticular synovial chondrosarcoma (*).

View larger version (160K): [in this window] [in a new window] [Download PPT slide]   Figure 16d.  Synovial chondrosarcoma in a 52-year-old man with a swollen knee in whom synovial osteochondromatosis had been diagnosed at biopsy 10 years earlier. (a) Lateral radiograph of the knee demonstrates distention of the joint space by a soft-tissue mass that contains areas of calcified matrix (arrows). (b) Axial CT scan of the knee demonstrates a large soft-tissue mass (*) in the joint space. Note the erosions of the distal femoral condyles (arrows), which are less apparent on the conventional radiograph. (c) Axial T1-weighted MR image demonstrates a large lobulated low-signal-intensity mass (*) distending the joint space, with erosion and invasion of the femoral condyles (arrows). (d) Axial T2-weighted MR image obtained more distally demonstrates high signal intensity (*) within the mass. (e, f) Precontrast (e) and postcontrast (f) sagittal T1-weighted MR images of the knee demonstrate heterogeneous enhancement of the infiltrating intraarticular synovial chondrosarcoma (*).

View larger version (149K): [in this window] [in a new window] [Download PPT slide]   Figure 16e.  Synovial chondrosarcoma in a 52-year-old man with a swollen knee in whom synovial osteochondromatosis had been diagnosed at biopsy 10 years earlier. (a) Lateral radiograph of the knee demonstrates distention of the joint space by a soft-tissue mass that contains areas of calcified matrix (arrows). (b) Axial CT scan of the knee demonstrates a large soft-tissue mass (*) in the joint space. Note the erosions of the distal femoral condyles (arrows), which are less apparent on the conventional radiograph. (c) Axial T1-weighted MR image demonstrates a large lobulated low-signal-intensity mass (*) distending the joint space, with erosion and invasion of the femoral condyles (arrows). (d) Axial T2-weighted MR image obtained more distally demonstrates high signal intensity (*) within the mass. (e, f) Precontrast (e) and postcontrast (f) sagittal T1-weighted MR images of the knee demonstrate heterogeneous enhancement of the infiltrating intraarticular synovial chondrosarcoma (*).

View larger version (157K): [in this window] [in a new window] [Download PPT slide]   Figure 16f.  Synovial chondrosarcoma in a 52-year-old man with a swollen knee in whom synovial osteochondromatosis had been diagnosed at biopsy 10 years earlier. (a) Lateral radiograph of the knee demonstrates distention of the joint space by a soft-tissue mass that contains areas of calcified matrix (arrows). (b) Axial CT scan of the knee demonstrates a large soft-tissue mass (*) in the joint space. Note the erosions of the distal femoral condyles (arrows), which are less apparent on the conventional radiograph. (c) Axial T1-weighted MR image demonstrates a large lobulated low-signal-intensity mass (*) distending the joint space, with erosion and invasion of the femoral condyles (arrows). (d) Axial T2-weighted MR image obtained more distally demonstrates high signal intensity (*) within the mass. (e, f) Precontrast (e) and postcontrast (f) sagittal T1-weighted MR images of the knee demonstrate heterogeneous enhancement of the infiltrating intraarticular synovial chondrosarcoma (*).

View larger version (175K): [in this window] [in a new window] [Download PPT slide]   Figure 17a.  Intraarticular synovial sarcoma in a 25-year-old man. (a) Sagittal proton density-weighted MR image demonstrates an intermediate-signal-intensity mass (arrow) in the anterior joint space. (b) Sagittal T2-weighted MR image with fat saturation demonstrates that the mass has high signal intensity (arrow). (c) Sagittal postcontrast T1-weighted MR image with fat saturation demonstrates enhancement of the mass (arrow). Note the foci of persistent low signal intensity with all pulse sequences, an appearance consistent with areas of calcification.

View larger version (166K): [in this window] [in a new window] [Download PPT slide]   Figure 17b.  Intraarticular synovial sarcoma in a 25-year-old man. (a) Sagittal proton density-weighted MR image demonstrates an intermediate-signal-intensity mass (arrow) in the anterior joint space. (b) Sagittal T2-weighted MR image with fat saturation demonstrates that the mass has high signal intensity (arrow). (c) Sagittal postcontrast T1-weighted MR image with fat saturation demonstrates enhancement of the mass (arrow). Note the foci of persistent low signal intensity with all pulse sequences, an appearance consistent with areas of calcification.

View larger version (147K): [in this window] [in a new window] [Download PPT slide]   Figure 17c.  Intraarticular synovial sarcoma in a 25-year-old man. (a) Sagittal proton density-weighted MR image demonstrates an intermediate-signal-intensity mass (arrow) in the anterior joint space. (b) Sagittal T2-weighted MR image with fat saturation demonstrates that the mass has high signal intensity (arrow). (c) Sagittal postcontrast T1-weighted MR image with fat saturation demonstrates enhancement of the mass (arrow). Note the foci of persistent low signal intensity with all pulse sequences, an appearance consistent with areas of calcification.

View larger version (162K): [in this window] [in a new window] [Download PPT slide]   Figure 18a.  Cyclops lesion in a patient after anterior cruciate ligament reconstruction. (a) Sagittal T1-weighted MR image of the knee with fat saturation demonstrates an intermediate-signal-intensity mass anteriorly in the joint space (arrow). (b) Sagittal T2-weighted MR image demonstrates the characteristic low signal intensity of this fibrous mass (arrow).

View larger version (178K): [in this window] [in a new window] [Download PPT slide]   Figure 18b.  Cyclops lesion in a patient after anterior cruciate ligament reconstruction. (a) Sagittal T1-weighted MR image of the knee with fat saturation demonstrates an intermediate-signal-intensity mass anteriorly in the joint space (arrow). (b) Sagittal T2-weighted MR image demonstrates the characteristic low signal intensity of this fibrous mass (arrow).