Synovial chondromatosis is the rare and benign metaplasia
of the synovial membrane resulting in the formation of multiple intra-articular
cartilaginous bodies. Synovial chondromatosis is known by several other
names including articular chondrosis and synovial chondrosis. This self-limited
and non-aggressive condition occurs most commonly in the knee followed
by the hip, shoulder and elbow. It presents during the third to fifth
decade twice as often in men than women and does not occur in children.
Synovial chondromatosis presents as the gradual onset of monoarticular
pain and stiffness. If allowed to continue, the slow, progressive symptoms
can result in decreased range of motion, effusions, crepitation and eventual
locking of the joint. This condition has also been described in the synovium,
soft tissue and bursae. Secondary synovial chondromatosis may be present
after long standing osteoarthritis.
There are several possible etiologies for synovial
chondromatosis. Trauma is supported by the fact that the process occurs
primarily in weight bearing and dominant upper extremity joints. Infection
is another possible culprit. Another theory postulates that cartilage
shed into the joint is taken up by the synovium.
The radiologic appearance of synovial chondromatosis
is usually that of radiopaque round or oval loose bodies within the joint.
Other radiologic signs include effusion, degenerative arthrosis, osteophytes
and subchondral sclerosis. CT scan is useful for viewing loose bodies
that may not have calcified and are not visible on plain x-ray. MRI demonstrates
multiple small filling defects and offers no real advantage over CT scan.
Bone scan has increased uptake around calcified loose bodies. Contrast
another option for delineating the presence of loose bodies. The differential
diagnosis of synovial chondromatosis includes septic arthritis, PVNS,
rheumatoid arthritis, osteoarthritis and synovial sarcoma.
On gross examination, there is diffuse or focal involvement
of the synovium with multiple nodules. The nodules are white-gray, translucent
hyaline cartilage and range in size from lmm to 3cm. Nodules are often
concentrated near the synovial cartilage junction and eventually break
free from the
synovium. Rarely, a large solitary nodule may be present which is referred
to as a giant solitary synovial chondromatosis. Primary synovial chondromatosis
will have a normal articular surface while secondary disease will have
a degenerative joint appearance.
Under the microscope, synovial chondromatosis appears
as focal islands of disorganized hyaline cartilage metaplasia in synovium.
This condition has aggressive cytologic features including enlarged chondrocytes,
hypercellularity and pleomorphic nuclei but is a benign, self limited
condition. Milgraml defined three phases of synovial chondromatosis: active
intrasynovial disease (metaplasia without loose bodies), transitional
lesions (metaplasia with loose bodies) and quiescent intrasynovial disease
(loose bodies without metaplasia). Nodules may calcify or ossify. In rare
cases, sarcomatous degeneration has occurred.
Treatment of synovial chondromatosis is controversial.
Options include arthroscopic synovectomy, open synovectomy and loose body
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