Osteosarcoma commonly spreads in three ways. The first is through hematogenous dissemination, meaning that tumor cells spread throughout the body via the bloodstream, a process known as hematogenous spread. The second method is called implantation metastasis, where tumor cells directly implant in the common sites of osteosarcoma, leading to localized disease. The third type is lymphatic spread, where tumor cells spread to multiple parts of the body through the lymphatic system, causing new tumor growth. These three pathways are the most common routes of metastasis seen clinically in osteosarcoma, with hematogenous spread being the most frequent.