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A
39-year-old man presents with a 6-month history of pain in
his right ankle. The pain has been insidious and is
accompanied by stiffness and swelling of the ankle joint.
The patient cannot move his ankle well. He cannot perform
his daily activities despite using a crutch.
The patient has no history of trauma. He does not have
fever, other joint involvement, or back pain. He has no
history of sexually transmitted diseases, and his family
history is negative for arthritis.
On physical examination, the patient has normal vital
signs, including temperature. Cardiac findings are negative
for murmurs or rubs. No rash or penile discharge is
observed. Examination of the right ankle elicits discomfort
and reveals physical limitation with inversion and eversion
and especially with flexion and extension. On palpation,
the patient has mild tenderness, and the swelling feels
firm. No warmth or redness is found over the joint. The
remainder of the physical examination yields unremarkable
results.
A plain radiograph of the ankle is obtained. What is the
diagnosis?
Answer
Synovial osteochondromatosis (SOC): SOC, also called
synovial chondromatosis, is typically a benign,
monoarticular proliferation of the synovial lining
of a joint, bursa, or tendon sheath with
cartilaginous metaplasia. Proliferation of the
synovium produces small nodules that break off and
migrate toward the joint cavity. After it becomes
intra-articular, metaplasia transforms the nodules
into cartilaginous bodies, which enlarge and which
typically undergo central necrosis. The necrotic
portion becomes calcified and eventually ossified to
various degrees. Large joints, such as the knee,
hip, elbow, and shoulder, are most commonly
affected. However, as this case illustrates, the
disease process can involve other joints. In fact,
any synovial surface, including extra-articular
bursae, may be affected.
As the condition progresses, the joint becomes
painfully distended with many such bodies, which may
number in the hundreds and which result in
mechanical symptoms of restricted motion with
eventual joint destruction and secondary
osteoarthritis.
The incidence of the disease is 2-4 times higher in
men with an age range of 20-50 years than in the
general population. SOC usually results in several
years of joint pain and swelling. At the time of
presentation, the affected joint often has limited
range of motion. The patient may also have a history
of the joint locking up. Malignant transformation
into chondrosarcoma is rarely reported and usually
occurs after repeated partial synovectomy
procedures.
Plain radiographs are commonly diagnostic,
demonstrating several ossified intra-articular loose
bodies. Features of osteoarthritis may be seen. In
the absence of ossified loose bodies, soft tissue
swelling may be appreciated; if so, a differential
diagnosis of pigmented villonodular synovitis may be
considered. CT scanning, if performed, shows the
same findings as radiography does, but CT scans may
reveal the nonossified loose bodies. MRI is the
modality of choice for demonstrating effusion,
synovial changes (which are hyperintense on
T2-weighted images with enhancement after the
administration of gadolinium-based contrast agent),
and loose bodies (which are isointense to
hypointense on T1-weighted images and which have
signal voids if they are ossified).
Treatment is synovectomy, though recurrences are
frequent unless total synovectomy is performed. The
patient in this case underwent partial synovectomy
with extraction of the loose intra-articular bodies.
He remained symptom-free at the time of this writing
several months after the procedure.
References
- Crotty
JM, Monu JU, Pope TL Jr. Synovial osteochondromatosis. Radiol
Clin North Am. 1996 Mar;34(2):327-42, xi.
- Pendse
NA, Diwan A, Menghani V. Synovial osteochondromatosis. Ind
J Radiol Imag. 2003;13(3):281-3.
- Resnick
D: Diagnosis of Bone and Joint Disorders. Philadelphia,
Pa: W.B. Saunders Company. 4th ed. 2002.
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Link
to further Information on:
For
more information on SOC, see the eMedicine article Synovial
Osteochondromatosis (within the Radiology specialty).
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