Age / Sex : 21 / M

Chief complaint: right knee pain for 1 year

1) What is your impression?

Two weeks later, you can see the final diagnosis with a brief discussion of this case.

(Quiz는 quiz일 뿐이오니 답안은 한개만 보내주시기 바라오며, 복수의 답안을 보내주시는 분은 정답이 포함되어 있더라도 부득이 semi-correct answer로 처리토록 하겠습니다.)

Courtesy: Lee In Sook (이인숙),  Pusan National University Hospital (부산대학교병원)

synovial osteochondromatosis

Discussion

Findings: plain radiograph of the knee shows conglomerated calcified nodules with chondroid-type within the joint. On sagittal T1-weighted MR image, low signal intensity lesion not well differentiated from the anterior cruciate ligament is seen. Foci of low signal on fat-suppressed sagittal proton density and contrast enhanced MR images are seen within the mass-like lesion, which correspond to calcified cartilage nodules seen on the plain radiograph.

Differential Diagnosis: rheumatoid arthritis (rice bodies), extra-skeletal cartilaginous tumors such as chondroma, tumoral calcinosis

Diagnosis: synovial osteochondromatosis

Discussion: primary synovial (osteo)chondromatosis is a benign disorder in which there is nodular cartilaginous metaplastic proliferation in synovium in joints. Secondary synovial chondromatosis occurs in the setting of other joint disorders such as degenerative osteoarthritis, avascular necrosis, osteochondritis dissecans, trauma/osteochondral fractures, tuberculosis, et al. solitary lesions can occur in both primary and secondary disorders and are referred to as synovial chondromas. They occurs most frequently between the ages of 25 to 65 years, mean 44 years. Also, they can also occur in children and older adults. Intra-articular sites are more common than extra-articular sites (bursae, tendon sheaths). In intra-articular sites, lesions occur in the knee joint (50-70%) > hip, elbow > shoulder > wrist, ankle > small joints > spinal synovial joints. Synovial osteochondromatosis typically appears as multiple nodules of various sizes with varying degrees of mineralization/calcification and ossification on plain radiograph. Large ossified lesions may show bony trabeculation with central radiolucent bone marrow. Small calcifications are seen better with CT than radiographs. Up to 30% of lesions may not show calcifications on radiographs. Non-calcified synovial chondromas may present as circumscribed mass-lesions with or  without lobulated margins. The MRI features are dependent on the relative proportions of cartilage, calcified cartilage, and mineralized osseous tissue within the lesions. calcifications results in low signal on T1WI, PDWI, T2WI and FST2WI. Extensive calcifications can appear as lesions with signal void. After Gd-contrast administration, they can show irregular, thin-peripheral and/or septal enhancement.

References:

1.     Meyers SP. Synovial chondromatosis, and synovial osteochondromatosis. In: MRI of bone and soft tissue tumors and tumorlike lesions: Differential diagnosis and atlas. New York, Thieme 2008:753-757

2.     Kramer J, Recht M, Deely DM, et al. MR appearance of idiopathic synovial osteochondromatosis. J Compt Assist Tomogr 1993;17:772-776

3.     Kransdorf MJ, Murphey MD. Synovial tumors. In: Imaging of soft tissue tumors 2^nd ed. Philadelphia, Pa:W.B. Saunders;2006:381-436