Osteosarcoma is a tumour that can originate in any bone and is the most frequent malignant tumour of the skeleton. It typically develops close to the metaphyseal growth plates in the limbs' long bones. The three most prevalent places are the femur, tibia, and humerus. Additional locations include the pelvis, skull, and jaw. Diaphyseal osteosarcoma involves a smaller population and is highly uncommon. Conventional kinds of osteosarcoma, such as osteoblastic, chondroblastic, and fibroblastic types, as well as telangiectatic, multifocal, parosteal, and periosteal types, are some of the variations of the disease. The primary bone tumour (cancerous) is generated by the formation of immature bone and primarily affects adolescents. We present a case of a 45-year-old menopausal female with left tibial osteosarcoma of the proximal 1/3 diaphysis infected with maggots and complaints of left knee pain and tingling.