(Radiographics. 2000;20:S263-S278.)
© RSNA, 2000
Multiregional Pathologic Processes |
Nonseptic Monoarthritis: Imaging Features with Clinical and Histopathologic Correlation1
Jaume Llauger, MD,
Jaume Palmer, MD,
Núria Rosón, MD,
Sílvia Bagué, MD,
Àngels Camins, MD and
Rosa Cremades, MD
1 From the Departments of Radiology (J.L., J.P., N.R., A.C., R.C.) and Pathology (S.B.), Hospital de la Santa Creu i Sant Pau, Avenida Sant Antoni M. Claret 167, 08025 Barcelona, Spain. Recipient of a Certificate of Merit award for a scientific exhibit at the 1999 RSNA scientific assembly. Received January 28, 2000; revision requested April 11 and received May 25; accepted May 30. Address correspondence to J.L. (e-mail: 17929jlr@comb.es).
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Abstract
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Diagnosis of septic arthritis requires aspiration and analysis of joint fluid. However, nonseptic articular disorders are fairly common and represent a significant diagnostic and therapeutic challenge. Such disorders include gout, Milwaukee shoulder, rapidly destructive articular disease, amyloid arthropathy, hemophilic arthropathy, primary synovial osteochondromatosis, pigmented villonodular synovitis, neuropathic arthropathy, and foreign-body synovitis. The clinical signs of articular disease, which include pain, swelling, and limitation of motion, are often nonspecific and can overlap with those of osseous or extraarticular disorders. Many articular processes have characteristic radiologic appearances that allow definitive diagnosis. Radiography is an important part of the evaluation of patients with articular disease. However, magnetic resonance (MR) imaging is the method of choice for characterizing the various disorders and assessing the full extent of osseous, chondral, and soft-tissue involvement. MR imaging can exquisitely demonstrate joint effusions, synovial proliferation, articular cartilage abnormalities, subchondral bone, ligaments, muscles, and juxtaarticular soft tissues. Although a wide spectrum of noninfectious processes may involve the joints, careful analysis of the imaging findings and correlation of these findings with the patient's clinical history can suggest a more specific diagnosis in most cases. Awareness and understanding of the underlying histopathologic findings aids in interpretation of MR images.
Index Terms: Amyloidosis, 40.68 • Arthritis, 40.70 • Calcium pyrophosphate dihydrate deposition disease (CPPD), 40.761 • Gout, 40.75 • Hemophilia, 40.6561 • Joints, diseases, 40.70 • Osteochondromatosis, 40.782 • Synovitis, 40.78
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Introduction
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In patients who present with a painful joint, especially children or patients with acute onset of symptoms, laboratory findings and joint aspiration are essential to make the diagnosis of septic arthritis. Routine radiographs are of limited usefulness in early diagnosis of this disease, and magnetic resonance (MR) imaging changes appear to be nonspecific, overlapping with findings seen in other inflammatory arthritides (1). However, in patients with chronic monoarticular or oligoarticular joint disease, radiography and MR imaging play a major role in evaluation and differential diagnosis of suspected arthritis and in staging, preoperative planning, and follow-up evaluation of documented arthritis. Owing to its superior soft-tissue contrast resolution and nonreformatted multiplanar imaging capability, MR imaging has become the modality of choice for evaluation of articular disorders. MR imaging can exquisitely demonstrate joint effusions, synovial proliferation, articular cartilage abnormalities, subchondral bone, ligaments, muscles, and juxtaarticular soft tissues.
In this article, the clinical and imaging features of the most common nonseptic monoarthritides or oligoarthritides are correlated with the gross and histologic characteristics. The specific entities discussed are gout, Milwaukee shoulder, rapidly destructive articular disease, amyloid arthropathy, hemophilic arthropathy, primary synovial osteochondromatosis, pigmented villonodular synovitis, neuropathic arthropathy, and foreign-body synovitis. The appearances at plain radiography and MR imaging are presented with particular emphasis on MR imaging findings that indicate or strongly suggest a specific diagnosis.
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Gout
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Gout is a metabolic disease characterized by an increase in serum urate concentration, episodes of acute arthritis, deposits of monosodium urate monohydrate crystals (tophi) within or around the joints, uric acid urolithiasis, and renal disease. Articular manifestations occur in the different stages of the disease and include acute arthritis, an intermediate phase, and chronic tophaceous gout. The diagnosis of acute monoarticular gouty arthritis is usually established with clinical and laboratory assessment. However, monoarticular or polyarticular forms of chronic tophaceous gout may present diagnostic difficulties, for which imaging evaluation is necessary. Chronic tophaceous gout occurs far more frequently in men than in women (20:1). It typically occurs in adults, usually in the 5th to 7th decades of life. The distribution of articular involvement in chronic tophaceous gout is variable and includes symmetric polyarticular disease resembling rheumatoid arthritis (2), asymmetric polyarticular disease, and monoarticular disease. Globally, the disease shows a predilection for the articulations of the lower extremities. The most common sites of abnormality are the feet, hands, wrists, elbows, and knees.
At histologic analysis, tophi are composed of crystalline or amorphous urates surrounded by a highly vascularized inflammatory tissue rich in histiocytes, lymphocytes, fibroblasts, and foreign-body giant cells.
Chronic tophaceous gout typically involves both joint and soft tissue. The tophi appear as eccentric or asymmetric soft-tissue masses around the joint. Calcification of a tophus is an unusual finding. Intraarticular or juxtaarticular bone erosions are very common, usually large, and frequently located beneath soft-tissue masses. Erosions are eccentrically located and frequently demonstrate sclerotic borders. Overhanging edges of bone are formed, which separate the tophaceous nodules from the adjacent erosions (Fig 1). In chronic tophaceous gout, juxtaarticular osteoporosis is not present and the joint space is preserved until late in the course of the disease. Most tophi are deposited in the periarticular soft tissue, although they may also be intraosseous (Fig 2), intraarticular (3), or extraarticular. Gouty tophi have a tendency toward deposition in or appearance in enthesis of extensor tendons such as the quadriceps, triceps, and Achilles tendon.
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Figure 1. Chronic tophaceous gout in a 63-year-old man with progressive swelling and pain in the distal interphalangeal joint. Anteroposterior radiograph of the finger shows eccentric bone erosions with overhanging margins (arrow), which are associated with nodular, noncalcified soft-tissue masses. The articular space is widened.
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Figure 2a. Chronic tophaceous gout with a large intraosseous tophus in a 43-year-old man with knee pain. (a) Anteroposterior radiograph shows an osteolytic lesion involving the internal condyle and intercondylar area of the distal femur with a well-defined sclerotic margin (arrows). There is no evidence of matrix mineralization. (b) Coronal T1-weighted MR image (repetition time msec/echo time msec, 550/15) shows a well-defined lesion of heterogeneous signal intensity with a scalloped margin (arrows), which communicates with the joint space. Marrow surrounding the lesion shows normal signal intensity. There are small erosions of the femoral condyles and adjacent soft-tissue masses (arrowheads), which presumably represent juxtaarticular tophi. (c) Photomicrograph (original magnification, x200; hematoxylin-eosin stain) shows a granulomatous response with histiocytes and foreign-body giant cells.
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Figure 2b. Chronic tophaceous gout with a large intraosseous tophus in a 43-year-old man with knee pain. (a) Anteroposterior radiograph shows an osteolytic lesion involving the internal condyle and intercondylar area of the distal femur with a well-defined sclerotic margin (arrows). There is no evidence of matrix mineralization. (b) Coronal T1-weighted MR image (repetition time msec/echo time msec, 550/15) shows a well-defined lesion of heterogeneous signal intensity with a scalloped margin (arrows), which communicates with the joint space. Marrow surrounding the lesion shows normal signal intensity. There are small erosions of the femoral condyles and adjacent soft-tissue masses (arrowheads), which presumably represent juxtaarticular tophi. (c) Photomicrograph (original magnification, x200; hematoxylin-eosin stain) shows a granulomatous response with histiocytes and foreign-body giant cells.
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Figure 2c. Chronic tophaceous gout with a large intraosseous tophus in a 43-year-old man with knee pain. (a) Anteroposterior radiograph shows an osteolytic lesion involving the internal condyle and intercondylar area of the distal femur with a well-defined sclerotic margin (arrows). There is no evidence of matrix mineralization. (b) Coronal T1-weighted MR image (repetition time msec/echo time msec, 550/15) shows a well-defined lesion of heterogeneous signal intensity with a scalloped margin (arrows), which communicates with the joint space. Marrow surrounding the lesion shows normal signal intensity. There are small erosions of the femoral condyles and adjacent soft-tissue masses (arrowheads), which presumably represent juxtaarticular tophi. (c) Photomicrograph (original magnification, x200; hematoxylin-eosin stain) shows a granulomatous response with histiocytes and foreign-body giant cells.
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At MR imaging, tophi have a wide spectrum of signal intensity characteristics, which reflect their variable composition and relative proportions of protein content, fibrous tissue, crystals, and hemosiderin (4). Most lesions are isointense relative to muscle on T1-weighted images. On T2-weighted images, most lesions show low to intermediate heterogeneous signal intensity (3,5), although lesions with high signal intensity have been reported (6). Homogeneous and intense enhancement is frequently observed on contrast material–enhanced images (Fig 3).
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Figure 3a. Monoarticular chronic tophaceous gout in a 73-year-old man with an enlarging mass in the dorsal aspect of the knee. (a) Anteroposterior radiograph shows diffuse soft-tissue swelling around the knee in association with multiple calcifications. (b) Computed tomographic (CT) scan of the distal femur shows multiple soft-tissue masses around the knee with punctate calcifications. (c, d) Axial T1-weighted (550/15) (c) and T2-weighted (2,200/80) (d) MR images of the proximal tibia show well-defined, lobulated masses around the joint. The signal intensity is similar to that of muscle on the T1-weighted image (c). The masses have predominantly low signal intensity and a more heterogeneous appearance on the T2-weighted image (d). Note the associated bone erosions (arrowheads). (e, f) Axial (e) and sagittal (f) T1-weighted MR images (550/15) obtained after administration of gadolinium contrast material show marked enhancement, which is more pronounced at the periphery of the lesions.
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Figure 3b. Monoarticular chronic tophaceous gout in a 73-year-old man with an enlarging mass in the dorsal aspect of the knee. (a) Anteroposterior radiograph shows diffuse soft-tissue swelling around the knee in association with multiple calcifications. (b) Computed tomographic (CT) scan of the distal femur shows multiple soft-tissue masses around the knee with punctate calcifications. (c, d) Axial T1-weighted (550/15) (c) and T2-weighted (2,200/80) (d) MR images of the proximal tibia show well-defined, lobulated masses around the joint. The signal intensity is similar to that of muscle on the T1-weighted image (c). The masses have predominantly low signal intensity and a more heterogeneous appearance on the T2-weighted image (d). Note the associated bone erosions (arrowheads). (e, f) Axial (e) and sagittal (f) T1-weighted MR images (550/15) obtained after administration of gadolinium contrast material show marked enhancement, which is more pronounced at the periphery of the lesions.
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Figure 3c. Monoarticular chronic tophaceous gout in a 73-year-old man with an enlarging mass in the dorsal aspect of the knee. (a) Anteroposterior radiograph shows diffuse soft-tissue swelling around the knee in association with multiple calcifications. (b) Computed tomographic (CT) scan of the distal femur shows multiple soft-tissue masses around the knee with punctate calcifications. (c, d) Axial T1-weighted (550/15) (c) and T2-weighted (2,200/80) (d) MR images of the proximal tibia show well-defined, lobulated masses around the joint. The signal intensity is similar to that of muscle on the T1-weighted image (c). The masses have predominantly low signal intensity and a more heterogeneous appearance on the T2-weighted image (d). Note the associated bone erosions (arrowheads). (e, f) Axial (e) and sagittal (f) T1-weighted MR images (550/15) obtained after administration of gadolinium contrast material show marked enhancement, which is more pronounced at the periphery of the lesions.
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Figure 3d. Monoarticular chronic tophaceous gout in a 73-year-old man with an enlarging mass in the dorsal aspect of the knee. (a) Anteroposterior radiograph shows diffuse soft-tissue swelling around the knee in association with multiple calcifications. (b) Computed tomographic (CT) scan of the distal femur shows multiple soft-tissue masses around the knee with punctate calcifications. (c, d) Axial T1-weighted (550/15) (c) and T2-weighted (2,200/80) (d) MR images of the proximal tibia show well-defined, lobulated masses around the joint. The signal intensity is similar to that of muscle on the T1-weighted image (c). The masses have predominantly low signal intensity and a more heterogeneous appearance on the T2-weighted image (d). Note the associated bone erosions (arrowheads). (e, f) Axial (e) and sagittal (f) T1-weighted MR images (550/15) obtained after administration of gadolinium contrast material show marked enhancement, which is more pronounced at the periphery of the lesions.
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Figure 3e. Monoarticular chronic tophaceous gout in a 73-year-old man with an enlarging mass in the dorsal aspect of the knee. (a) Anteroposterior radiograph shows diffuse soft-tissue swelling around the knee in association with multiple calcifications. (b) Computed tomographic (CT) scan of the distal femur shows multiple soft-tissue masses around the knee with punctate calcifications. (c, d) Axial T1-weighted (550/15) (c) and T2-weighted (2,200/80) (d) MR images of the proximal tibia show well-defined, lobulated masses around the joint. The signal intensity is similar to that of muscle on the T1-weighted image (c). The masses have predominantly low signal intensity and a more heterogeneous appearance on the T2-weighted image (d). Note the associated bone erosions (arrowheads). (e, f) Axial (e) and sagittal (f) T1-weighted MR images (550/15) obtained after administration of gadolinium contrast material show marked enhancement, which is more pronounced at the periphery of the lesions.
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Figure 3f. Monoarticular chronic tophaceous gout in a 73-year-old man with an enlarging mass in the dorsal aspect of the knee. (a) Anteroposterior radiograph shows diffuse soft-tissue swelling around the knee in association with multiple calcifications. (b) Computed tomographic (CT) scan of the distal femur shows multiple soft-tissue masses around the knee with punctate calcifications. (c, d) Axial T1-weighted (550/15) (c) and T2-weighted (2,200/80) (d) MR images of the proximal tibia show well-defined, lobulated masses around the joint. The signal intensity is similar to that of muscle on the T1-weighted image (c). The masses have predominantly low signal intensity and a more heterogeneous appearance on the T2-weighted image (d). Note the associated bone erosions (arrowheads). (e, f) Axial (e) and sagittal (f) T1-weighted MR images (550/15) obtained after administration of gadolinium contrast material show marked enhancement, which is more pronounced at the periphery of the lesions.
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Milwaukee Shoulder
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Milwaukee shoulder was described by McCarty et al (7) in 1981 and consists of the association of complete tear of the rotator cuff, osteoarthritic changes, noninflammatory joint effusion containing calcium hydroxyapatite and calcium pyrophosphate dihydrate crystals, hyperplasia of the synovium, destruction of cartilage and subchondral bone, and multiple osteochondral loose bodies. This entity most frequently affects older women and manifests clinically as a rapidly progressive and destructive arthritis of the shoulder. A history of trauma is frequently reported. Changes of calcium pyrophosphate dihydrate crystal deposition disease involving the knees are commonly noted (8).
This arthropathy manifests as joint space narrowing, subchondral sclerosis with cyst formation, destruction of subchondral bone, soft-tissue swelling, capsular calcifications, and intraarticular loose bodies. MR imaging demonstrates a large effusion, a complete rotator cuff tear, narrowing of the glenohumeral joint, thinning of cartilage, and destruction of subchondral bone (Fig 4).
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Figure 4a. Milwaukee shoulder in a 77-year-old woman with pain and limitation of motion in the left shoulder. (a) Anteroposterior radiograph shows soft-tissue swelling and irregular calcifications (arrow) around the shoulder. Anterior dislocation is noted. (b) Coronal T2-weighted MR image (2,100/ 80) shows a large joint effusion, resorption and deformity of the humeral head, and complete rupture of the rotator cuff.
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Figure 4b. Milwaukee shoulder in a 77-year-old woman with pain and limitation of motion in the left shoulder. (a) Anteroposterior radiograph shows soft-tissue swelling and irregular calcifications (arrow) around the shoulder. Anterior dislocation is noted. (b) Coronal T2-weighted MR image (2,100/ 80) shows a large joint effusion, resorption and deformity of the humeral head, and complete rupture of the rotator cuff.
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Rapidly Destructive Articular Disease
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Rapidly destructive articular disease is an unusual form of osteoarthritis (9) that typically involves the hip. The disease is almost always unilateral, but bilateral lesions and concomitant unilateral or bilateral destructive arthritis of the shoulder have also been reported (10). Radiographs of other joints frequently demonstrate more conventional osteoarthritic changes in the hands, wrists, knees, and opposite hips. Rapidly destructive hip disease most frequently affects elderly women and manifests clinically as hip pain. Most affected patients will require total joint replacement as treatment after rapid destruction of the hip, which occurs an average of 14 months after the onset of symptoms, in contrast to the slower course of typical osteoarthritis. The differential diagnosis includes several articular disorders that can lead to rapid destruction of a large joint, such as osteonecrosis, septic arthritis, neuroarthropathy, or crystal-induced arthropathies.
Histologic examination of the resected femoral head shows severe osteoarthritic changes and fails to demonstrate significant osteonecrosis, significant inflammatory changes, microorganisms, or crystals.
Serial radiographs show progressive loss of joint space and loss of subchondral bone in the femoral head and acetabulum, resulting in marked flattening and deformity of the femoral head ("hatchet" deformity). Superolateral subluxation of the femoral head or intrusion deformity within the ilium can be observed. Most cases demonstrate subchondral defects and mild sclerosis (Fig 5). However, osteophytes are small or absent.
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Figure 5a. Rapidly destructive arthropathy of the hip in a 66-year-old woman. (a) Anteroposterior radiograph of the hip obtained before the onset of symptoms shows mild osteoarthritic changes. (b) Radiograph obtained after 6 months of progressive pain shows flattening of the femoral head with superolateral subluxation, multiple subchondral defects, bone sclerosis, and narrowing of the articular space.
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Figure 5b. Rapidly destructive arthropathy of the hip in a 66-year-old woman. (a) Anteroposterior radiograph of the hip obtained before the onset of symptoms shows mild osteoarthritic changes. (b) Radiograph obtained after 6 months of progressive pain shows flattening of the femoral head with superolateral subluxation, multiple subchondral defects, bone sclerosis, and narrowing of the articular space.
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Amyloid Arthropathy
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Amyloidosis is defined as the extracellular deposition of the fibrous protein amyloid in one or more sites in the body. ß2-microglobulin was described as a new form of amyloid protein in 1986 (11). This low-molecular-weight serum protein is not filtered by standard dialysis membranes and tends to accumulate within the musculoskeletal system. ß2-microglobulin–related amyloid arthropathy is seen in patients undergoing long-term hemodialysis. Amyloid arthropathy may involve the axial skeleton, especially the cervical spine, or the peripheral skeleton. Patients with ß2-microglobulin–related amyloidosis can also develop carpal tunnel syndrome and osteolytic bone lesions (amyloidomas) (12). Shoulder pain and carpal tunnel syndrome are the most common clinical manifestations. These symptoms are commonly bilateral.
In the glenohumeral joint and other large joints, amyloid arthropathy resembles inflammatory arthritis with juxtaarticular soft-tissue swelling, mild periarticular osteoporosis, and subchondral cystic lesions, usually with well-defined sclerotic margins. Usually, the joint space is normal in width until late in the course of the disease (Fig 6). Patients with amyloidomas of bone or with large subchondral lesions have a high prevalence of pathologic fractures (12,13). The MR imaging appearance of amyloid infiltration within or around the joint consists of extensive deposition of an abnormal soft tissue that has low or intermediate signal intensity on T1-weighted images and low to intermediate signal intensity on T2-weighted images (13,14). This abnormal material covers the synovial membrane, fills subchondral defects, and extends to periarticular soft tissue. Joint effusion is usually present.
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Figure 6a. Amyloid arthropathy of the shoulder in a 55-year-old man who underwent long-term hemodialysis. (a) Anteroposterior radiograph shows diffuse soft-tissue swelling around the shoulder in association with small erosions in the humeral head (arrow). (b) Sagittal T1-weighted MR image (500/15) shows extensive periarticular deposition of an abnormal soft tissue that is isointense relative to skeletal muscle and extends into subchondral defects (arrow). (c) Axial gradient-echo MR image (400/18, 25° flip angle) shows distention of the subdeltoid bursa and an erosion of the anterior humeral head, which contains material of signal intensity less than that of fluid.
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Figure 6b. Amyloid arthropathy of the shoulder in a 55-year-old man who underwent long-term hemodialysis. (a) Anteroposterior radiograph shows diffuse soft-tissue swelling around the shoulder in association with small erosions in the humeral head (arrow). (b) Sagittal T1-weighted MR image (500/15) shows extensive periarticular deposition of an abnormal soft tissue that is isointense relative to skeletal muscle and extends into subchondral defects (arrow). (c) Axial gradient-echo MR image (400/18, 25° flip angle) shows distention of the subdeltoid bursa and an erosion of the anterior humeral head, which contains material of signal intensity less than that of fluid.
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Figure 6c. Amyloid arthropathy of the shoulder in a 55-year-old man who underwent long-term hemodialysis. (a) Anteroposterior radiograph shows diffuse soft-tissue swelling around the shoulder in association with small erosions in the humeral head (arrow). (b) Sagittal T1-weighted MR image (500/15) shows extensive periarticular deposition of an abnormal soft tissue that is isointense relative to skeletal muscle and extends into subchondral defects (arrow). (c) Axial gradient-echo MR image (400/18, 25° flip angle) shows distention of the subdeltoid bursa and an erosion of the anterior humeral head, which contains material of signal intensity less than that of fluid.
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Hemophilic Arthropathy
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Classic hemophilia (hemophilia A) and Christmas disease (hemophilia B) may be associated with repeated bleeding into the synovial joints and subsequent arthropathic changes. In descending order, the knee, ankle, elbow, and shoulder are the most commonly affected joints. Bilateral involvement is common, although a single joint is usually involved in each episode of bleeding. Hemophilic arthropathy most often occurs in the 1st or 2nd decade of life. Bleeding episodes tend to recur in the same joint and cause synovial hyperplasia, chronic inflammatory changes, fibrosis, and siderosis of the synovial membrane. Musculoskeletal involvement in patients with hemophilia also includes repetitive bleeding into the muscles, which causes joint contractures or soft-tissue pseudotumors, and bleeding into the bones, which results in osseous pseudotumors.
Radiographic findings vary greatly with the different stages of hemophilic arthropathy (acute, subacute, or chronic hemarthrosis) and reflect the presence of hemarthrosis (joint effusion), synovial inflammation and hyperemia (osteoporosis and epiphyseal overgrowth), chondral erosions and subchondral resorption (osseous erosions and cysts), cartilaginous denudation (joint space narrowing), intraosseous or subperiosteal hemorrhage (pseudotumors), and osseous proliferation (sclerosis and osteophytosis) (15). Some abnormalities of osseous shape, such as widening of the intercondylar notch, flattening of the condylar surface, or squaring of the patella, are very characteristic of chronic hemarthrosis of the knee (Fig 7). At MR imaging, hypertrophied synovial membrane resulting from repetitive hemarthrosis has characteristic low signal intensity with all pulse sequences, especially with gradient-echo sequences, due to the magnetic susceptibility effect caused by hemosiderin (16) (Fig 8). As in pigmented villonodular synovitis, the signal intensity of the subarticular defects varies and may indicate the presence of fluid (high signal intensity on T2-weighted images), soft tissue (intermediate signal intensity), or synovial tissue with hemosiderin (low signal intensity) (17).
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Figure 7. Hemophilic arthropathy in an 11-year-old boy with repetitive hemarthrosis. Anteroposterior radiograph of the knee shows extensive osteoporosis, enlargement of the epiphyses, mild irregularities of the subchondral bone, and a widened intercondylar notch (arrows).
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Figure 8a. Chronic hemophilic arthropathy of the knee in a 35-year-old man with hemophilia A. Sagittal T1-weighted (500/15) (a) and axial gradient-echo (400/18, 25° flip angle) (b) MR images show thickened synovial tissue with very low signal intensity due to hemosiderin deposits and to scar and fibrous tissue formation.
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Figure 8b. Chronic hemophilic arthropathy of the knee in a 35-year-old man with hemophilia A. Sagittal T1-weighted (500/15) (a) and axial gradient-echo (400/18, 25° flip angle) (b) MR images show thickened synovial tissue with very low signal intensity due to hemosiderin deposits and to scar and fibrous tissue formation.
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Primary Synovial Osteochondromatosis
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Primary synovial osteochondromatosis is a benign monoarticular disorder of unknown origin characterized by proliferation and metaplastic transformation of the synovium, with formation of multiple cartilaginous or osteocartilaginous nodules within the joints, bursae, or tendon sheaths. The knee is the most commonly affected joint, followed by the elbow, hip, and shoulder, although any other joint may be involved (18). Knee involvement accounts for more than 50% of all cases. Bilateral involvement of the knees is estimated to occur in about 10% of cases (19). Primary synovial osteochondromatosis uncommonly occurs within a tendon sheath or bursa. Synovial osteochondromatosis that develops within a bursa overlying an osteochondroma may simulate malignant transformation of the osteochondroma (20). Patients usually present with pain, swelling, and limitation of motion, which often progress slowly for several years. The age range of affected patients is wide, but most present in the 4th or 5th decade of life. Men are affected two to four times more frequently than women. Primary synovial osteochondromatosis is usually progressive and leads to early osteoarthritis, but it may be self-limiting. Removal of the intraarticular bodies is the preferred treatment, although local recurrence is not uncommon. Clinical and radiographic manifestations of primary synovial osteochondromatosis may be confused with those of other causes of intraarticular loose bodies (secondary osteochondromatosis), such as trauma, osteoarthritis, osteonecrosis, and neuropathic arthropathy.
At pathologic analysis, synovial osteochondromatosis consists of multiple nodules of hyaline cartilage attached to the synovium. These nodules may detach to form loose bodies. At microscopic examination, the nodules are hypercellular and contain chondrocytes with different degrees of nuclear atypia (21). Cartilaginous bodies may contain cartilage alone, cartilage and bone, or mature bone with fatty marrow. The histologic appearance varies from an active initial phase, with active synovial proliferation without loose bodies, to a final phase, which is characterized by inactive synovial disease and remaining loose bodies (19). Malignant transformation in synovial osteochondromatosis is rare but has been reported (22).
The radiologic appearance of primary or idiopathic synovial chondromatosis depends on the stage of disease and on the extent of calcification or ossification of the cartilaginous nodules. In its most distinctive appearance, multiple small, well-defined, juxtaarticular nodules of uniform size are observed (Fig 9). In other cases, a large, amorphously mineralized juxtaarticular mass is present (Fig 10). Calcification is absent in approximately 25%–30% of patients. In these cases, plain radiographs may be normal or may reveal a nonspecific soft-tissue mass surrounding the joint, widening of the joint space, erosions of adjacent bones, or early osteoarthritic changes (Fig 11). Osteoporosis is typically absent. CT may demonstrate multiple calcified or ossified intraarticular bodies or an intraarticular mass of near water attenuation with multiple small calcifications.
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Figure 9a. Primary synovial osteochondromatosis of the shoulder in a 25-year-old woman. (a) Anteroposterior radiograph of the shoulder shows multiple calcified bodies in the glenohumeral joint. The joint space is normal. (b) CT scan of the humeral head shows multiple intraarticular ossified nodules with a peripheral rim of cortical bone. (c) Sagittal T1-weighted MR image (550/15) shows multiple bodies of uniform size with peripheral low signal intensity and central high signal intensity, which indicate the presence of cortical bone and marrow fat, respectively. (d) Photograph of the specimens shows multiple bodies of uniform size covered by whitish-blue hyaline cartilage.
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Figure 9b. Primary synovial osteochondromatosis of the shoulder in a 25-year-old woman. (a) Anteroposterior radiograph of the shoulder shows multiple calcified bodies in the glenohumeral joint. The joint space is normal. (b) CT scan of the humeral head shows multiple intraarticular ossified nodules with a peripheral rim of cortical bone. (c) Sagittal T1-weighted MR image (550/15) shows multiple bodies of uniform size with peripheral low signal intensity and central high signal intensity, which indicate the presence of cortical bone and marrow fat, respectively. (d) Photograph of the specimens shows multiple bodies of uniform size covered by whitish-blue hyaline cartilage.
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Figure 9c. Primary synovial osteochondromatosis of the shoulder in a 25-year-old woman. (a) Anteroposterior radiograph of the shoulder shows multiple calcified bodies in the glenohumeral joint. The joint space is normal. (b) CT scan of the humeral head shows multiple intraarticular ossified nodules with a peripheral rim of cortical bone. (c) Sagittal T1-weighted MR image (550/15) shows multiple bodies of uniform size with peripheral low signal intensity and central high signal intensity, which indicate the presence of cortical bone and marrow fat, respectively. (d) Photograph of the specimens shows multiple bodies of uniform size covered by whitish-blue hyaline cartilage.
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Figure 9d. Primary synovial osteochondromatosis of the shoulder in a 25-year-old woman. (a) Anteroposterior radiograph of the shoulder shows multiple calcified bodies in the glenohumeral joint. The joint space is normal. (b) CT scan of the humeral head shows multiple intraarticular ossified nodules with a peripheral rim of cortical bone. (c) Sagittal T1-weighted MR image (550/15) shows multiple bodies of uniform size with peripheral low signal intensity and central high signal intensity, which indicate the presence of cortical bone and marrow fat, respectively. (d) Photograph of the specimens shows multiple bodies of uniform size covered by whitish-blue hyaline cartilage.
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Figure 10a. Primary synovial osteochondromatosis of the hip in a 44-year-old man. (a) Axial radiograph shows a large mineralized mass surrounding the proximal aspect of the femur. (b) Axial T2-weighted MR image (2,000/80) shows an intraarticular mass (arrows) with nodular areas of increased and decreased signal intensity. Note the associated small joint effusion.
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Figure 10b. Primary synovial osteochondromatosis of the hip in a 44-year-old man. (a) Axial radiograph shows a large mineralized mass surrounding the proximal aspect of the femur. (b) Axial T2-weighted MR image (2,000/80) shows an intraarticular mass (arrows) with nodular areas of increased and decreased signal intensity. Note the associated small joint effusion.
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Figure 11a. Primary synovial chondromatosis of the wrist in a 36-year-old man. (a) Anteroposterior radiograph shows diffuse soft-tissue swelling around the wrist in association with erosions of the adjacent bones (arrows). (b, c) Axial T1-weighted (500/15) (b) and T2-weighted (2,000/80) (c) MR images show a lobulated mass surrounding the wrist. The mass demonstrates signal intensity similar to that of muscle on the T1-weighted image (b) and heterogeneous intermediate to high signal intensity on the T2-weighted image (c). (d) Low-power photomicrograph (original magnification, x40; hematoxylin-eosin stain) shows rounded cellular islands of hyaline cartilage within the connective tissue of the joint capsule (arrows).
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Figure 11b. Primary synovial chondromatosis of the wrist in a 36-year-old man. (a) Anteroposterior radiograph shows diffuse soft-tissue swelling around the wrist in association with erosions of the adjacent bones (arrows). (b, c) Axial T1-weighted (500/15) (b) and T2-weighted (2,000/80) (c) MR images show a lobulated mass surrounding the wrist. The mass demonstrates signal intensity similar to that of muscle on the T1-weighted image (b) and heterogeneous intermediate to high signal intensity on the T2-weighted image (c). (d) Low-power photomicrograph (original magnification, x40; hematoxylin-eosin stain) shows rounded cellular islands of hyaline cartilage within the connective tissue of the joint capsule (arrows).
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Figure 11c. Primary synovial chondromatosis of the wrist in a 36-year-old man. (a) Anteroposterior radiograph shows diffuse soft-tissue swelling around the wrist in association with erosions of the adjacent bones (arrows). (b, c) Axial T1-weighted (500/15) (b) and T2-weighted (2,000/80) (c) MR images show a lobulated mass surrounding the wrist. The mass demonstrates signal intensity similar to that of muscle on the T1-weighted image (b) and heterogeneous intermediate to high signal intensity on the T2-weighted image (c). (d) Low-power photomicrograph (original magnification, x40; hematoxylin-eosin stain) shows rounded cellular islands of hyaline cartilage within the connective tissue of the joint capsule (arrows).
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Figure 11d. Primary synovial chondromatosis of the wrist in a 36-year-old man. (a) Anteroposterior radiograph shows diffuse soft-tissue swelling around the wrist in association with erosions of the adjacent bones (arrows). (b, c) Axial T1-weighted (500/15) (b) and T2-weighted (2,000/80) (c) MR images show a lobulated mass surrounding the wrist. The mass demonstrates signal intensity similar to that of muscle on the T1-weighted image (b) and heterogeneous intermediate to high signal intensity on the T2-weighted image (c). (d) Low-power photomicrograph (original magnification, x40; hematoxylin-eosin stain) shows rounded cellular islands of hyaline cartilage within the connective tissue of the joint capsule (arrows).
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At MR imaging, different patterns may also be noted (23). Nonmineralized lesions (synovial chondromatosis) tend to form a periarticular conglomerate mass that is isointense or slightly hyperintense relative to skeletal muscle on T1-weighted images and hyperintense to muscle on T2-weighted images (Fig 11). These lesions must be distinguished from a large effusion or a soft-tissue tumor. The presence of septations and the characteristic peripheral and septal enhancement of chondral lesions after intravenous administration of gadolinium contrast material may be useful to confirm the diagnosis. When chondroid masses contain calcifications, small areas of signal void are observed with all pulse sequences. Finally, intraarticular bodies with mature bone and fatty marrow show a central area with imaging characteristics similar to those of fat (high signal intensity on T1-weighted images). Joint effusion is uncommon or not relevant.
In secondary osteochondromatosis, the intraarticular bodies tend to be larger, less numerous, and more varied in size than in primary synovial osteochondromatosis. Secondary osteochondromatosis typically demonstrates associated and more prominent changes of the underlying degenerative disease of the joint.
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Pigmented Villonodular Synovitis
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Pigmented villonodular synovitis and giant cell tumors of the tendon sheath represent a diverse group of benign proliferative disorders of the synovium that may affect the joints, bursae, or tendon sheaths (24). These disorders have similar histologic features and are considered related entities but are distinguished by differences in clinical course, radiologic manifestations, treatment, and prognosis. Their origin is unknown, although a benign neoplasm or an inflammatory process have been suggested as causes. Pigmented villonodular synovitis represents the diffuse and intraarticular form of this spectrum of disorders. Pigmented villonodular synovitis occurs most frequently in the knee (80% of cases). The second most common location is the hip. Less commonly, it occurs in the ankle, shoulder, and elbow. Other anatomic locations, as well as polyarticular involvement (25), are extremely rare. Pigmented villonodular synovitis is usually seen in young adults, with a peak presentation between the 3rd and 4th decades of life; men and women are equally affected. Patients typically present with swelling, stiffness, and progressive pain in the involved joint. Aspirated fluid is typically xanthochromic or serosanguineous. Involvement of the shoulder typically occurs in older patients and is characterized by the absence of serosanguineous effusion (26). Local recurrence following surgical or arthroscopic synovectomy occurs in almost 50% of cases. Malignant transformation has been reported, although it is an extremely rare and controversial entity (27).
At gross examination, pigmented villonodular synovitis consists of many villous or frondlike synovial proliferations with a characteristic tan or reddish color caused by deposition of hemosiderin within the lesion. At microscopic examination, the lesions are seen to be composed of solid or fingerlike masses of hyperplastic synovium. In the active or early phase of the disease, multinucleated giant cells, small vessels, lymphocytes, xanthoma cells, and relatively small amounts of intra- and extracellular hemosiderin are noted, suspended in a fibroblastic stroma. In this phase, usually found in younger patients, thickening of the synovium is more obvious and effusion is always present (Fig 12). Fibrosis, chronic inflammation, and hyalinization are the dominant histologic features of long-standing chronic lesions (28), with absence of the characteristic villous proliferations. However, synovial accumulation of hemosiderin is more significant (Fig 13).
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Figure 12a. Pigmented villonodular synovitis of the knee in a 14-year-old boy. (a) Lateral radiograph shows soft-tissue swelling around the knee without osseous involvement. (b) Sagittal proton-density-weighted MR image (2,200/20) shows a large effusion and diffusely hypertrophied synovium (arrows). (c) Sagittal T2-weighted MR image (2,200/80) shows the fluid, which has high signal intensity, and the abnormal synovial tissue, which has low signal intensity due to hemosiderin deposits. (d) Photograph of the excised synovium shows numerous frondlike proliferations with a characteristic reddish color.
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Figure 12b. Pigmented villonodular synovitis of the knee in a 14-year-old boy. (a) Lateral radiograph shows soft-tissue swelling around the knee without osseous involvement. (b) Sagittal proton-density-weighted MR image (2,200/20) shows a large effusion and diffusely hypertrophied synovium (arrows). (c) Sagittal T2-weighted MR image (2,200/80) shows the fluid, which has high signal intensity, and the abnormal synovial tissue, which has low signal intensity due to hemosiderin deposits. (d) Photograph of the excised synovium shows numerous frondlike proliferations with a characteristic reddish color.
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Figure 12c. Pigmented villonodular synovitis of the knee in a 14-year-old boy. (a) Lateral radiograph shows soft-tissue swelling around the knee without osseous involvement. (b) Sagittal proton-density-weighted MR image (2,200/20) shows a large effusion and diffusely hypertrophied synovium (arrows). (c) Sagittal T2-weighted MR image (2,200/80) shows the fluid, which has high signal intensity, and the abnormal synovial tissue, which has low signal intensity due to hemosiderin deposits. (d) Photograph of the excised synovium shows numerous frondlike proliferations with a characteristic reddish color.
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Figure 12d. Pigmented villonodular synovitis of the knee in a 14-year-old boy. (a) Lateral radiograph shows soft-tissue swelling around the knee without osseous involvement. (b) Sagittal proton-density-weighted MR image (2,200/20) shows a large effusion and diffusely hypertrophied synovium (arrows). (c) Sagittal T2-weighted MR image (2,200/80) shows the fluid, which has high signal intensity, and the abnormal synovial tissue, which has low signal intensity due to hemosiderin deposits. (d) Photograph of the excised synovium shows numerous frondlike proliferations with a characteristic reddish color.
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Figure 13a. Pigmented villonodular synovitis of the hip in a 58-year-old man with a 5-year history of progressive pain and limitation of motion. (a) Anteroposterior radiograph shows narrowing of the joint space and multiple subchondral lytic defects on both sides of the joint. (b) Coronal gradient-echo MR image (450/18, 25° flip angle) shows tissue of very low signal intensity outlining the joint capsule. (c) Photomicrograph (original magnification, x200; Perls stain) shows that the synovium maintains a papillary configuration but is considerably more fibrous and less cellular. Prominent deposition of hemosiderin is noted.
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Figure 13b. Pigmented villonodular synovitis of the hip in a 58-year-old man with a 5-year history of progressive pain and limitation of motion. (a) Anteroposterior radiograph shows narrowing of the joint space and multiple subchondral lytic defects on both sides of the joint. (b) Coronal gradient-echo MR image (450/18, 25° flip angle) shows tissue of very low signal intensity outlining the joint capsule. (c) Photomicrograph (original magnification, x200; Perls stain) shows that the synovium maintains a papillary configuration but is considerably more fibrous and less cellular. Prominent deposition of hemosiderin is noted.
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Abstract
Introduction
