Synovial Sarcoma Disguised as a Ganglion Cyst in a Patient with Chronic Knee Pain.

Introduction: An uncommon malignant soft-tissue tumor, synovial sarcoma (SS) usually develops close to large joints like the knee and ankle, and most frequently affects young adults. These tumors might be confused for benign intra-articular lesions such as pigmented villonodular synovitis, synovial osteochondromatosis, or ganglion cysts because they frequently manifest as slow-growing, painless masses. The diagnostic difficulties and significance of taking SS into account when making a differential diagnosis for chronic intra-articular lesions are highlighted by this case. Case Report: A 25-year-old man from South India came in complaining of right knee pain and limited flexion that had gotten worse for 6 months. Physiotherapy has not alleviated his symptoms in the past. Although the quality of the initial imaging was poor, it showed a cystic lesion close to the lateral femoral condyle. A clinical examination revealed a limited range of motion (0-100°), point discomfort over the lateral femoral condyle, and no indications of joint instability or effusion. Arthroscopic excision of the lesion was done, followed by Radio and Chemotherapy. According to MRI and PET CT, the patient was still disease-free and had good knee function 14 months after surgery. A Yearly follow-up was recommended for him due to the possibility of a late relapse. Conclusion: Prompt diagnosis and the best possible care depend on early surgical intervention and comprehensive histological assessment. To prevent treatment delays and enhance patient outcomes, clinicians should take SS consideration when establishing a differential diagnosis for any persistent or unusual intra-articular mass, especially in young adults.