Rare presentation of primary intra-articular synovial sarcoma of knee joint with insights from literature review

ABSTRACT Synovial sarcoma is a rare and malignant soft tissue tumor, comprising 5%–10% of such cases. This tumor primarily afflicts adolescents and young adults, with slight male bias, often near large joints like the knee and hip. Intra-articular synovial sarcoma, an even rarer subset, can delay diagnosis due to its slow growth and vague clinical signs. We present a unique case of primary knee intra-articular synovial sarcoma in a 24-year-old female. Imaging revealed a distinct lesion adjacent to the medial femoral condyle and patellofemoral joint, initially suggestive of synovial haemangioma. However, histopathology confirmed biphasic synovial sarcoma, characterized by spindle and gland-like epithelial components. Immunohistochemistry further supported the diagnosis. Reviewing documented cases, we find that synovial sarcoma can affect a wide age range but often occurs in the knee joint, emphasizing the need for vigilance. Early detection and intervention are crucial for improved treatment outcomes in this rare but challenging malignancy.