Presentation
Chronic limping and claudication with difficult control of knee movement. MRI knee was requested.
Patient Data
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Signal void, lobulated cystic lesion in the popliteal fossa connected to the popliteal artery with associated extensive muscular and subcutaneous edema. Moderate knee joint effusion.
On the MRI a popliteal fossa lesion with signal void alerts us to perform a color Doppler ultrasound examination. This revealed a high flow popliteal artery aneurysm. CTA was urgently requested.
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Contrast filled aneurysmal sac in the popliteal fossa communicated anteriorly with the popliteal artery via a narrow curved short neck. No leakage of contrast out of the sac. No thrombosis and or arterial branches originating from it.
Incidentally the liver is cirrhotic. Splenectomy. Contrast filled esophageal varices with mesenteric and retroperitoneal edema.
Case Discussion
The usual imaging requested for a patient with knee pain is MRI to examine ligaments and menisci as well as articular cartilage and other extra-articular structure. Popliteal fossa lesions rarely cause alarming knee pain
The most common cystic lesion seen in the popliteal fossa is a Baker's cyst with aneurysms (both true and false) being uncommon. Endovascular coiling is the treatment of choice.