Double synovial cyst of the proximal tibiofibular joint confirmed by MRI as a cause of the peroneal tunnel syndrome.

The aim of this case report is to present an unusual double synovial cyst that arose from the proximal tibiofibular joint compressing the peroneal nerve in the peroneal tunnel and was unrecognized at the beginning. According to the review of literature back to 1891, only 62 cases of cysts originating from the proximal tibiofibular joint (PTFJ) have been described. We report a case of a 32 year old male patient who was admitted to the Department of Orthopaedic Surgery because of a classic peroneal tunnel syndrome of the left leg. On the lateral side of the proximal third of his left leg a tumefaction of 12 x 2.5 cm was visible. The sonography showed a characteristic image of the para-articular synovial cyst of the left knee. A surgical extirpation of the synovial cyst and decompression of the peroneal nerve in the peroneal tunnel were performed. PHD confirmed a classic synovial cyst. Postoperatively, the symptoms of the peroneal nerve compression disappeared. Three years after the first surgical intervention the patient was readmitted to the Department because of quite similar problems, only the neurological symptoms were less intensive than during the first admittance. This time the performed MR imaging showed a double synovial cyst originating from the proximal tibiofibular joint. The surgical treatment consisted of a total extirpation of both cysts including the narrow stalks of communication with the PTFJ. The joint was opened and a synovectomy was done using an electrocauter and a sharp curette. Regular check-ups were done every 6 months and twice during the control period of 4 years, as was the MR imaging control. MRI findings 4 years after the second surgical intervention were normal. Clinical findings after 7 years were normal and we are sure that the recidivation of the synovial cyst excluded. The MRI diagnostics was crucial for an adequate surgical treatment and the relief of the peroneal tunnel syndrome symptoms.