Synovial cysts of the proximal tibiofibular joint: three case reports.

Synovial cysts are fluid-filled masses lined with synovium and located within or about joints. The main symptoms are pain and/or neurological deficits. They can be intraneural or extraneural or develop between or within muscles. Synovial cysts that arise at a distance from a joint raise diagnostic challenges. We report three cases of synovial cysts of the proximal tibiofibular joint, including an intramuscular cyst responsible for paralysis of the anterolateral leg muscles. Tibiofibular synovial cysts are less common than popliteal cysts, and their pathophysiology is poorly understood. Pressure on the common peroneal nerve is the main complication and requires careful surgical excision of the cyst. Injection of a glucocorticoid into the cyst can be used as the first-line treatment in patients without common peroneal nerve symptoms.