Swelling Over Left Anterior Knee

For 2 months, a 29-year-old man had pain and circular, soft swelling (7 x 7 cm in diameter) over the anterior left knee, superficial to the patellar ligament. Your dx?

For 2 months, a 29-year-old man had pain and circular, soft swelling (7 x 7 cm in diameter) over the anterior left knee, superficial to the patellar ligament. Pain was minimal and associated with extension and flexion.

Your dx?