A rare case of a posttraumatic extensive ganglion cyst of the anterolateral thigh with connection to the knee joint is presented. A 54-year-old man presented a palpable mass in the anterolateral region of his right thigh with a 15 months existing sense of fullness and tightness. He had an accident with his bicycle 21 months ago. Magnetic resonance imaging (MRI) was performed showing a cyst inside the quadriceps femoris muscle between vastus lateralis and intermedius with connection to recessus suprapatellaris and knee joint. In addition MRI detected a traumatic lesion in the quadriceps femoris tendon in the near of the knee joint. The ganglion cyst was 18 cm long and was excised completely. Intraoperatively, the knee joint connection was confirmed and excised as well. The ganglion cyst was filled with a gelatinous and viscous fluid.
Keywords: ganglion cyst; knee joint.; post-traumatic; quadriceps femoris tendon.