一位83岁的女性患者出现了右膝侧面逐渐增大一年的病史。磁共振成像显示右膝皮下组织内有一个巨大的软组织肿瘤。由于肿瘤出血，右膝的肿块迅速增大。通过穿刺活检，确诊为滑膜肉瘤。患者接受了广泛切除手术，并使用腓骨长肌腱进行了侧副韧带重建。最新的随访中，患者的肌骨瘤协会评分为86%。总之，在软组织切除肉瘤后，使用腓骨长肌腱进行侧副韧带重建可能有助于保护膝关节功能。

An 83-year-old woman presented with a 1-year history of a growing mass on the lateral surface of the right knee. Magnetic resonance imaging revealed a large soft tissue tumor in the subcutis of the right knee. The mass in the right knee rapidly increased, due to hemorrhage from the tumor. A needle biopsy revealed that the diagnosis was synovial sarcoma. The patient underwent wide excision and lateral collateral ligament reconstruction using the plantaris tendon. The patient had a Musculoskeletal Tumor Society Score of 86% at the lateset follow-up. In conclusion, reconstruction of the lateral collateral ligament using the plantaris tendon may be useful for preserving the function of the knee joint after resection of the soft tissue due to sarcoma of the knee.Copyright: © Tsuha et al.