In a setting where many older patients or patients with osteoarthritis
are seen, osterorthritic cysts in periarticular bones will be commonly
seen . Patients often have pain in the affected joint because of
the osteoarthritis, and the radiographs reveal what may seem to be a destructive
To differentiate between these benign entities and a true bone tumor or
a metastatic cancer deposit in bone, look for the following features:
1) The lesion is right next to the joint. Careful examination
of the radiographs may reveal an actual communication between the joint
space and the cyst cavity. If doubt about the nature of the lesion
exists, a fine cut CT scan on the area may allow this communicating opening
to be seen and help establish the true diagnosis.
2) There are radiographically visible signs of osteoarthritis, usually
moderate but sometimes mild, seen in the adjacent joint. If these
are entirely absent, the diagnosis should be reconsidered.
3)There is usually a sclerotic rim around some areas of the lesion.
The zone of transition is narrow, whereas in a metastatic lesion
4) The lesion should be fluid filled, and this may be seen best on MRI
5) These lesions are rareloy progressive, and pathological fractures
Treatment should be directed towards the cause, which is the lesion in
the nearby joint, usually OA or sometimes a meniscus or ligament tear,
or a ttaumatic cartilage defect. At the Umass Memorial Medical Center,
we have been using minimally invasive surgery to treat these lesions when
they are symptomatic.