Musculoskeletal ImagingPigmented villonodular synovitis
a proliferative disorder of the
synovial membrane that most commonly involves the knee, hip, elbow and ankle. A brown fluid can frequently be aspirated from the joint, which reflects haemosiderin deposits from chronic
haemorrhage or fresh blood from acute
haemorrhage.
Radiographs often show the classic but not invariable findings of joint effusion, preservation of joint space, the absence of osteoporosis and the presence or absence of bone erosions and cysts. Bone erosions and subchondral cysts can be prominent, particularly in the hip, ankle, elbow and wrist. Many of the radiographic features of diffuse intra-articular pigmented villonodular synovitis are identical to those occurring in cases of idiopathic synovial chondromatosis. If calcification is present, however, generally pigmented villonodular synovitis can be ruled out.
A giant cell tumour of a tendon sheath represents a nodular lesion of tendon sheaths, usually in the hand or foot, which may sometimes be confused with some forms of pigmented villonodular synovitis because of similar histologic findings. The radiographic features are somewhat different in these two conditions, however. In pigmented villonodular synovitis, a diffuse or localized soft tissue mass is observed, with subjacent erosion of bone. On MR images, the deposition of haemosiderin in cases of pigmented villonodular synovitis leads to dramatic abnormalities characterized by regions of low signal intensity on both T1- and T2-weighted spin-echo MR images.
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