High-resolution Ultrasound in Diagnosis and Intervention of an Incidentally Detected Anterior Cruciate Ligament Ganglion Cyst in a Patient of Osteoarthritis Knee

A 45-year-old woman with bilateral knee osteoarthritis presented with posterior knee pain and restricted end-range motion. High-resolution ultrasound revealed a rounded cystic lesion in the intercondylar fossa that dynamically shifted position with knee flexion, appearing anteriorly beneath the patellar tendon within Hoffa’s fat pad. MRI confirmed mucoid degeneration of the anterior cruciate ligament (ACL) with associated ganglion cyst. Ultrasound-guided aspiration with corticosteroid injection was performed, followed by structured rehabilitation, resulting in significant pain reduction and improved knee mobility at a 1-month follow-up. This case emphasizes the diagnostic value of dynamic ultrasound scanning from both anterior and posterior approaches in differentiating ACL ganglion cysts from other intra-articular or periarticular lesions. The incidental detection of an ACL ganglion cyst in a patient with osteoarthritis underscores the role of ultrasound not only as a cost-effective alternative to MRI but also as a tool for real-time guided intervention.