AUTHOR AND EDITOR INFORMATION

Section 1 of 10  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT Scan
• MRI
• Nuclear Medicine
• Intervention
• Multimedia
• References

INTRODUCTION

Section 2 of 10  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT Scan
• MRI
• Nuclear Medicine
• Intervention
• Multimedia
• References

Background

Synovial osteochondromatosis (SOC) is a benign condition characterized by synovial membrane proliferation and metaplasia. The entity also is termed synovial chondromatosis. The synovial lining of a joint, bursa, or tendon sheath undergoes nodular proliferation, and fragments may break off from the synovial surface into the joint. There, nourished by synovial fluid, the fragments may grow, calcify, or ossify. The intra-articular fragment may vary in size from a few millimeters to a few centimeters.

The degree of calcification varies, and calcification may be seen as a few calcific specks or as foci of frankly ossified bodies. The fragments may be found free within the joint cavity, or they may be embedded within the proliferating synovium, which may extend into the surrounding soft tissues. The natural history of SOC entails gradual progression of disease, joint deterioration, and secondary osteoarthritis. Essentially, the disease is a benign process, and although studies in the literature have reported malignant transformation, this finding is decidedly unusual.

Pathophysiology

SOC is characterized by synovial membrane metaplasia, hyperplasia, and hyaline or myxoid change. The synovial lining of a joint, bursa, or tendon sheath undergoes nodular proliferation, and fragments may break off from the synovial surface into the joint. In this location, where they are nourished by synovial fluid, the fragments may grow, calcify, or ossify.

Mortality/Morbidity

Generally, SOC is a monoarticular disease that has a benign course. Several reports in the literature describe malignant transformation. The transformations occurred after several recurrences following treatment.

Sex

SOC shows a predilection of 2- to 4-fold for males over females.

Age

Individuals of all ages can be affected, but the disease is often diagnosed in persons aged 20-50 years.

Clinical Details

Patients with SOC often relate a history of several years of joint pain with swelling. The affected joint frequently has an associated limitation in range of motion and/or a history of locking. SOC is almost always a monoarticular process, and the large joints are more commonly affected. These include the knee, hip, elbow, and shoulder. However, the disease process may affect any synovial surface, including the extra-articular bursa.

SOC shows a predilection for males that is 2- to 4-fold greater than that for females; most patients with SOC present in the third to fifth decades of life.

If the intra-articular fragments are adequately calcified, the diagnosis is easily made with plain radiographic examination. With noncalcified fragments, magnetic resonance imaging (MRI) scans are required to show the nature and extent of SOC.

Purists differentiate primary, or idiopathic, SOC from the secondary form. In secondary SOC, the initial predisposing factor is an unrelated articular process leading to joint disintegration, production of intra-articular fragments, synovitis, and, eventually, synovial metaplasia. The cause of primary SOC is unknown.

Preferred Examination

Radiographic findings are frequently diagnostic. Computed tomography (CT) scans and CT arthrograms also may be used, especially for demonstrating noncalcified intra-articular bodies. MRI usually helps establish the diagnosis, and the images demonstrate the true extent of the disease. Ultrasonographic examination may be used to investigate accessible joints.

Radiographs should be obtained first. MRI scans should then be obtained preoperatively. When MRI is not readily available, CT arthrography may be performed.

Limitations of Techniques

Radiographs may not demonstrate noncalcified bodies. CT scans may not demonstrate the full extent of proliferating synovial disease. SOC may be confused with pigmented villonodular synovitis (PVNS) if only MRI scans are available, and plain radiographs may help in such cases.

DIFFERENTIALS

Section 3 of 10  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT Scan
• MRI
• Nuclear Medicine
• Intervention
• Multimedia
• References

Other Problems to Be Considered

Rice bodies of tuberculosis and rheumatoid arthritis 
Synovial hemangioma

RADIOGRAPH

Section 4 of 10  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT Scan
• MRI
• Nuclear Medicine
• Intervention
• Multimedia
• References

Findings

Plain radiographs frequently show characteristic features, including multiple (usually >5) calcified or osseous bodies within the joint or bursa. When fragments are not calcified, intrasynovial fragments may not be seen on plain images, and arthrographic studies are required to demonstrate the bodies.

Pressure erosions (saucerization) and cyst formation can be seen in adjacent bone, although this is more typical for joints with lax capsules, such as the hip. A similar observation may be found in patients with PVNS.

Degree of Confidence

With plain radiography, differential diagnoses include degenerative joint disease in which osteophytes have broken off into the joint; however, SOC tends to have a larger number of bodies in the joint (usually >5). Other differential diagnoses include soft-tissue and intra-articular chondromas. In advanced stages of SOC, secondary degenerative changes are often observed.

CT SCAN

Section 5 of 10  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT Scan
• MRI
• Nuclear Medicine
• Intervention
• Multimedia
• References

Findings

CT scanning is rarely necessary to make a diagnosis, and the CT scan's features are similar to findings on plain radiographs. CT scanning may show noncalcified bodies.

MRI

Section 6 of 10  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT Scan
• MRI
• Nuclear Medicine
• Intervention
• Multimedia
• References

Findings

In SOC, T1-weighted and proton density–weighted images often demonstrate multiple rounded bodies that are isointense or hypointense relative to muscle. Some bodies demonstrate signal intensity (or lack of it) similar to that of cortical bone.

Some bodies may lie free, and some are completely intra-articular, whereas others may be adherent to the synovial surface. Some bodies may be found deep in the synovial lining, embedded in adjacent soft tissue.

T2-weighted images may show areas of high signal intensity consistent with joint effusion and synovial thickening.

The intravenous administration of a gadolinium-based contrast material usually enables the differentiation of joint effusion from hyperplastic synovium, which shows heterogeneous enhancement.

Gadolinium-based contrast agents (gadopentetate dimeglumine [Magnevist], gadobenate dimeglumine [MultiHance], gadodiamide [Omniscan], gadoversetamide [OptiMARK], gadoteridol [ProHance]) have recently been linked to the development of nephrogenic systemic fibrosis (NSF) or nephrogenic fibrosing dermopathy (NFD). For more information, see the eMedicine topic Nephrogenic Fibrosing Dermopathy. The disease has occurred in patients with moderate to end-stage renal disease after being given a gadolinium-based contrast agent to enhance MRI or magnetic resonance angiography scans. As of late December 2006, the Food and Drug Administration (FDA) had received reports of 90 such cases. Worldwide, over 200 cases have been reported, according to the FDA. NSF/NFD is a debilitating and sometimes fatal disease. Characteristics include red or dark patches on the skin; burning, itching, swelling, hardening, and tightening of the skin; yellow spotson the whites of the eyes; joint stiffness with trouble moving or straightening the arms, hands, legs, or feet; pain deep in the hip bones or ribs; and muscle weakness. For more information, see the FDA Public Health Advisory or Medscape.

Joint effusion may be hemorrhagic.

The distinguishing feature of SOC is calcification, which appears as signal voids in the synovium. This finding is optimally visualized when the intra-articular fragments are calcified.

Degree of Confidence

When the presence of calcification is ambiguous, plain radiographs are useful adjuncts to MRI scans for establishing the diagnosis.

False Positives/Negatives

On MRI scans, SOC may appear somewhat similar to PVNS, but the 2 conditions are easily differentiated by using plain radiographs.

NUCLEAR MEDICINE

Section 7 of 10  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT Scan
• MRI
• Nuclear Medicine
• Intervention
• Multimedia
• References

Findings

Radionuclide studies may be obtained when the plain radiographic features are not clear. The affected areas usually show increased radionuclide uptake on technetium-99m bone scans.

INTERVENTION

Section 8 of 10  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT Scan
• MRI
• Nuclear Medicine
• Intervention
• Multimedia
• References

The treatment of patients with SOC involves surgical excision of the proliferating synovium. Because recurrence is frequent after surgery, total synovectomy has been suggested as the preferred treatment for the condition.

MULTIMEDIA

Section 9 of 10  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT Scan
• MRI
• Nuclear Medicine
• Intervention
• Multimedia
• References

Media file 1:  Plain radiograph of a 19-year-old man who initially presented with a history of shoulder pain of insidious onset. The patient was found to have synovial osteochondromatosis. Frontal radiograph of the shoulder shows multiple rounded, calcified bodies in the axillary recess and in the subscapularis bursa.
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Media file 2:  Magnetic resonance imaging (MRI) scan of a 19-year-old man who initially presented with a history of shoulder pain of insidious onset. The patient was found to have synovial osteochondromatosis. Coronal T1-weighted image of the shoulder shows multiple hypointense foci in the axillary recess and in the subacromial space. Note the hypointense foci deep to the deltoid in the subdeltoid bursa. The foci result from the presence of osteocartilaginous bodies in these areas. Cartilage bodies may be present in the sleeve of the biceps tendon.
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Media type:  MRI

Media file 3:  Magnetic resonance imaging (MRI) scan of a 19-year-old man who initially presented with a history of shoulder pain of insidious onset. The patient was found to have synovial osteochondromatosis. Oblique sagittal proton density– and T2-weighted images show multiple, rounded, hypointense foci in the subscapularis bursa projecting underneath the coracoid process. Note the high signal intensity simulating the presence of surrounding fluid from the joint effusion. Some of the high signal intensity results from edematous proliferating synovium. The synovium is dissecting the body of the scapula and the infraspinatus. Note the solitary osteochondral body in that location.
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Media type:  MRI

Media file 4:  Magnetic resonance imaging (MRI) scan of a 19-year-old man who initially presented with a history of shoulder pain of insidious onset. The patient was found to have synovial osteochondromatosis. Oblique sagittal proton density– and T2-weighted images show multiple, rounded, hypointense foci in the subscapularis bursa projecting underneath the coracoid process. Note the high signal intensity simulating the presence of surrounding fluid from the joint effusion. Some of the high signal intensity results from edematous proliferating synovium. The synovium is dissecting the body of the scapula and the infraspinatus. Note the solitary osteochondral body in that location.
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Media type:  MRI

Media file 5:  Image from a 19-year-old man who initially presented with a history of shoulder pain of insidious onset. The patient was found to have synovial osteochondromatosis. Some of the multiple stones were removed from the patient's shoulder during surgery. Note the lamellate pattern to the chondral bodies.
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Media type:  Image

Media file 6:  Frontal radiograph of the knee shows multiple calcified bodies in the proximal tibiofibular joint in a patient with synovial osteochondromatosis.
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Media type:  X-RAY

Media file 7:  Lateral radiograph of the knee shows multiple calcified bodies in the proximal tibiofibular joint in a patient with synovial osteochondromatosis.
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Media type:  X-RAY

Media file 8:  Frontal radiograph of a patient with synovial osteochondromatosis of the knee joint. The bodies are located in the popliteal space of the knee.
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Media type:  X-RAY

Media file 9:  Lateral radiograph of a patient with synovial osteochondromatosis of the knee joint. The bodies are located in the popliteal space of the knee.
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Media type:  X-RAY

Media file 10:  Lateral view of the ankle of a man who presented with ankle discomfort. Increased soft-tissue density is noted both anteriorly and posteriorly, simulating joint effusion. Note the stippled calcification seen posteriorly, resulting from calcification in some of the cartilage bodies. The anterior corner of the distal tibia is truncated as a result of pressure erosion. Similar pressure erosions may be seen in hip and knee joints in which synovial osteochondromatosis occurs. Note the mild osteopenia around the ankle; this is likely a result of hyperemia.
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Media type:  X-RAY

Media file 11:  Delayed bone scan shows diffusely increased uptake around the tibiotalar joint. This indicates increased metabolic activity and is consistent with synovitis around the ankle.
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Media type:  Image

Media file 12:  Sagittal T1-weighted and sagittal short-tau inversion recovery (STIR) images of the ankle show proliferating synovium, which is seen as foci of increased signal intensity on the STIR images.
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Media type:  MRI

Media file 13:  Sagittal T1-weighted and sagittal short-tau inversion recovery (STIR) images of the ankle show proliferating synovium, which is seen as foci of increased signal intensity on the STIR images.
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Media type:  MRI

Media file 14:  Lateral radiograph of the elbow of a 29-year-old man who presented with locking and reduced range of motion of the elbow. Soft-tissue fullness simulating effusion is noted. In addition, rounded, calcified bodies are seen both anteriorly and posteriorly around the elbow.
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Media type:  X-RAY

Media file 15:  Axial computed tomography (CT) images of the elbow at the level of the radial ulna joint. Note the presence of osteocartilaginous bodies in the radial ulna joint and also posteriorly.
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Media type:  CT

Media file 16:  Sagittal reconstruction from a spiral computed tomography (CT) scan series of the elbow shows the distribution of the calcified bodies in the olecranon fossa and around the posterior and anterior aspects of the joint.
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Media type:  CT

REFERENCES

Section 10 of 10

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT Scan
• MRI
• Nuclear Medicine
• Intervention
• Multimedia
• References

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Article Last Updated: Jun 21, 2007