Most popliteal cysts are asymptomatic. However, cysts may rupture, resulting in pain and swelling of the leg that could also arise from other diseases, including deep vein thrombosis, lymphedema, cellulitis, and tear of a muscle or tendon. Therefore, it is difficult to diagnose a ruptured popliteal cyst based on only a patient's history and physical examination. Musculoskeletal ultrasound has been regarded as a diagnostic tool for ruptured popliteal cyst. Here, we describe a patient who was rapidly diagnosed as ruptured popliteal cyst by ultrasonography. Therefore, ultrasound could be used to distinguish a ruptured popliteal cyst from other diseases in patients with painful swollen legs before evaluation for deep vein thrombosis.
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Baker cyst is an enlargement of the gastrocnemius-semimembranosus bursa. Neuropathy can occur due to either direct compression from the cyst itself or indirectly after cyst rupture. We report a unique case of a 49-year-old man with left sole pain and paresthesia who was diagnosed with posterior tibial neuropathy at the lower calf area, which was found to be caused by a ruptured Baker cyst. The patient's symptoms resembled those of lumbosacral radiculopathy and tarsal tunnel syndrome. Posterior tibial neuropathy from direct pressure of ruptured Baker cyst at the calf level has not been previously reported. Ruptured Baker cyst with resultant compression of the posterior tibial nerve at the lower leg should be included in the differential diagnosis of patients who complain of calf and sole pain. Electrodiagnostic examination and imaging studies such as ultrasonography or magnetic resonance imaging should be considered in the differential diagnosis of isolated paresthesia of the lower leg.
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