Infra-patellar fat pad cysts are an uncommon type of intra-articular ganglia. We report a case of a young woman with a painful little mass in the anterior aspect of the left knee. Ultrasound revealed a multiloculate cyst, that was initially drained with a spinal needle. Four months later, she had a recurrence of symptoms and a ultrasound guided aspiration was performed. Cytological examination revealed synovial cells, synovial fluid, macrophages and debris: diagnosis was ganglion cyst. We reviewed the literature about infra-patellar fat pad cysts. Clinical diagnosis of an intraarticular cyst is very difficult, but sometimes an infra-patellar fat pad cyst could be suspected because it could be visible and palpable. MRI is the best diagnostic option in all cases. There are several treatment option, operative or conservative. In our opinion ultrasound guided aspiration is the treatment of choice in symptomatic ganglia, because it allows to drain all lacunae, preventing recurrence.
Keywords: Hoffa cyst; Hoffa ganglia; infra patellar fat pad cyst; infra patellar ganglia; intra articular ganglia.