Pes Anserine Ganglion Cyst as a Rare Cause of Chronic Medial Knee Pain: A Case Report.

Ganglion cysts are benign mucin-filled pseudocysts most commonly encountered in the wrist and hand, while intra-articular ganglion cysts of the knee are rare, particularly those arising near the pes anserine bursa. Their nonspecific presentation often overlaps with more common causes of medial knee pain, leading to diagnostic delay. We report the case of a 43-year-old woman who presented with progressively worsening, atraumatic medial knee pain over several months with a largely unremarkable physical examination. Plain radiographs were normal, while magnetic resonance imaging demonstrated a well-circumscribed, multilobulated cystic lesion adjacent to the pes anserine bursa without associated meniscal or ligamentous pathology. Due to persistent symptoms despite conservative management, arthroscopic excision was performed, confirming a ganglion cyst on gross pathology. The patient experienced complete resolution of symptoms without recurrence at the six-week follow-up. This case highlights the importance of considering pes anserine ganglion cysts in the differential diagnosis of chronic medial knee pain and underscores the critical role of MRI in accurate diagnosis and surgical planning.