Osteosarcoma, characterized as an osteoid-producing neoplasm, is a highly malignant tumor that occurs predominantly in the metaphysis of long bones, often in the distal femur and proximal tibia. More rarely, osteosarcomas can develop in soft tissue. Although the malignancy usually develops in the medullary cavity of the metaphysis of a growing long tubular bone, less frequent growth patterns may develop on the surface of the bone. Superficial osteosarcomas, in addition to being significantly rarer, are also low-grade, while medullary osteosarcomas are aggressive in nature, making it high-grade. Osteosarcomas may also be confined to the cortex and may also originate in an extraskeletal location. EITHOLOGY AND PREVALENCE Despite ongoing research, the cause of osteosarcoma is still unknown. Occurring in 2 people per million per year (Michael et al., 2006), osteosarcoma is the most common primary bone tumor, but its incidence among malignancies is rare. However, there are numerous factors that have been shown to influence prevalence. Osteosarcoma occurs predominantly in males, although the tumor has a tendency to develop earlier in females (American Cancer Society, 2014). The risk of osteosarcoma is greatest for people between the ages of 10 and 30. However, the most common risk is during the adolescent growth period, due to rapid bone growth and the increased likelihood of a mutation in DNA replication. Height can also be a risk factor. Children with osteosarcoma are generally tall for their age, again indicating a link to rapid bone growth. It also appears that osteosarcoma has a slightly higher prevalence in African Americans than in other races. There is also evidence that genetic predisposition is a risk... halfway through the article... pain and weakening of the bone would not allow the system to function as effectively. Furthermore, the lower limb often functions as a closed chain, so if an osteosarcoma developed in the distal femur or proximal tibia, walking would be made difficult and thus one would have a limp. Limitation of the joints. As discussed previously, bone weakness and associated pain inhibit movement of the limbs, including the joints. Although joint involvement is uncommon in osteosarcoma, as the articular cartilage constitutes a relative barrier to tumor invasion, there is evidence that the cancer causes joint effusion that prevents normal joint movement (Quan G, et al. 2005). osteosarcoma progresses, the bone may weaken to such an extent that a fracture may occur, however the end of the fracture will only occur in the later stages of osteosarcoma.