SYNOVIAL CHONDROMATOSIS



Sagittal T1 and Coronal STIR images show gross effusion of suprapatellar bursa and mild knee joint effusion with synovial thickening and multiple chondral bodies- s/o synovial chondromatosis





·        Divided into primary and secondary forms.

·        Primary form was originally considered to represent chondroid metaplasia in the synovium of a joint with resultant formation of multiple intraarticular chondral bodies. However, current cytogenetic evaluation demonstrates that primary synovial chondromatosis is a benign neoplastic process.

·        An identical process can also involve the synovium that extends along tendons and bursae and is referred to as tenosynovial or bursal chondromatosis, respectively.

·        Secondary form is associated with joint abnormalities, such as mechanical or arthritic conditions, that cause intraarticular chondral bodies.

·        Primary synovial chondromatosis typically affects adults, predominantly men, in the third to fifth decades of life.

·        Knee is the most commonly affected site.

·        Radiographs reveal multiple intraarticular calcifications, and the calcifications are innumerable and uniform with typical even distribution throughout the joint.

·        Chondroid ring-and-arc pattern of mineralization is common.

·        Target appearance: A central focus and a single peripheral rim of calcification.

·        Juxtaarticular osteopenia is typically absent unless there is disuse.

·        Joint space is preserved unless there there is arthritis due to recurrent disease.

·        Extrinsic erosion of bone, usually on both sides of the joint.

·        Tenosynovial and bursal chondromatosis demonstrate findings similar to those observed in intraarticular disease.

·        Peripheral and septal enhancement may be seen following intravenous administration of contrast material. This finding represents enhancement of the vascularized synovium and fibrous septations between the relatively avascular cartilaginous nodules.

·        MRI patterns

1.     Lobulated, homogeneous, intermediate, intraarticular signal intensity similar to that of muscle on T1-weighted images, with high signal intensity on T2-weighted images and focal areas of low signal intensity with all pulse sequences.

2.     The second most common pattern (14% of cases) was similar to the first, but no focal intraarticular areas of low signal intensity and no calcifications were seen on corresponding radiographs or CT scans.

3.     The third had features similar to those of the other patterns but also included high-signal-intensity foci isointense relative to fat with a peripheral rim of low signal intensity.

·        MR imaging can also depict bursal extension of intraarticular primary synovial chondromatosis.

·        Malignant transformation is rare.

·        Local recurrence of primary synovial chondromatosis is not infrequent.

·        Distinguishing recurrent disease from malignant transformation can be difficult.

·        However, rapid increase in the size of the lesion in a patient with known primary synovial chondromatosis or a rapidly deteriorating clinical course should prompt suspicion of malignant transformation and biopsy of the lesion.

·        Metastases to the lungs are a clear sign of malignancy and unfortunately may represent the clinical feature that is convincing evidence of the diagnosis.

Reference : Imaging of Synovial Chondromatosis with Radiologic-Pathologic Correlation, September 2007 RadioGraphics.