Intra-articular tumors of the wrist should be considered as a possible cause of generalized wrist swelling, pain, and stiffness. Plain radiographs often do not provide many clues to the underlying diagnosis. CT or MRI will show the extent of the disease, but the hand surgeon may still confuse the tumor with an inflammatory process such as rheumatoid arthritis or gout (Fig. 8). The features of the axial images must be reviewed carefully, just as the surgeon would critically examine any abnormal tissue seen intraoperatively.
Pigmented villonodular synovitis (PVNS) is a benign tumor characterized by synovial hyper-plasia and a proliferation of multinucleated giant cells. Hemosiderin is found within the cells and surrounding tissues, creating a pigmented tan or brownish-yellow appearance to the lesions. Grossly, PVNS occurs in two forms, nodular and diffuse. Both forms may occur in young to middle-aged adults around the synovial sites of the hand.
PVNS is usually encountered by hand surgeons in its nodular form, a localized nodular tenosyn-ovitis, also known as giant cell tumor of the tendon sheath. These circumscribed lesions are most common about the palmar surfaces of the fingers, and may erode into the underlying bone . The diffuse form of the disease occurs in the wrist and, although much less common [53,54], it has the same ability to invade local tissues [55-59].
PVNS of the wrist causes a mildly painful swollen joint. Aspiration yields dark-brown, hem-orrhagic synovial fluid that suggests the diagnosis. Plain radiographs show carpal bone erosions or cysts, but intralesional calcifications are uncommon. As a result, the true extent of the mass is not readily apparent on radiographs, and the diagnosis is often delayed. Carpintero  and colleagues reported a case initially misdiagnosed as an intra-osseous ganglion.
Cross-sectional imaging reveals the diagnosis by demonstrating the intra-articular soft tissue mass responsible for the effusion and carpal bone findings. On CT examination the mass is hyper-dense secondary to frequent hemorrhage and blood breakdown products. On MRI the mass may demonstrate the full spectrum of signal intensity, depending on the region of the tumor. Acute bleeding will have high signal intensity on T2-weighted images, whereas hemosiderin has low signal intensity on T1 and T2 sequences.
Overall, MRI allows preoperative planning for resection of the soft tissue mass, whereas CT examination facilitates management of changes in the bony architecture.
PVNS of the wrist is treated by a complete synovectomy, including dorsal and volar incisions as needed. Acute carpal tunnel syndrome  or more chronic median neuropathy  may need to be addressed concurrently. It is worthwhile in joints with minimal destruction to attempt curet-tage and bone grafting of carpal cysts. If tumor remains, the graft may resorb and the disease may progress, necessitating limited or total wrist ar-throdesis for pain relief .
Synovial chondromatosis is a metaplastic process of periarticular synovium, resulting in the formation of hyaline cartilage bodies. The cartilage bodies are usually gray-white in color, several millimeters in size, and found imbedded within the proliferative synovial membrane or free within the intra-articular space. The result is a painful, swollen joint, typically in a young to middle-aged adult—similar to PVNS. Loose bodies may cause catching or locking and ultimately arthritis from articular wear.
Synovial chondromatosis about the carpus is rare, but it must be considered in the differential of a painful, swollen, and stiff wrist. Loonen and Schuurman  recently reviewed the literature and identified 24 cases of synovial chondromato-sis of the wrist, in addition to one of their own. Both the radiocarpal and distal radioulnar joints may be affected [62,63].
Plain radiographs often show characteristic calcified cartilaginous nodules, facilitating differentiation from PVNS and other synovial diseases. CT scan will further delineate calcified bodies that are not visible on plain radiograph. Both CT and MRI reveal the true extent of the disease, and may detect the early changes of secondary arthritis that inevitably occur. Synovial chondromatosis with secondary arthritic changes should not be confused with the more common clinical scenario of primary osteoarthritis with osteophytes, subchon-dral sclerosis, and loose osteochondral fragments.
The treatment of synovial chondromatosis involves synovectomy and removal of loose bodies. Symptoms improve with surgery, and few recurrences have been reported. Bone erosions and cysts are uncommon compared with PVNS, but secondary arthritic changes may need to be addressed, particularly if disease recurs .
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