Stem cell research holds significant potential to enhance treatments for common sports injuries, especially in tissues with low healing capacity. This chapter discusses the theoretical background of stem cells and progenitor cells, providing an overview of the different types of stem cells and their respective differentiation capabilities. It explores the evolving definitions and criteria for mesenchymal stem cells (MSCs). We compare the most commonly used sources of autologous stem cells (adipose tissue and bone marrow) in clinical trials and clinical application, highlighting that adipose-derived stem cells, obtained via minimally invasive liposuction, are safer and yield more viable cells with higher proliferative capabilities than bone marrow-derived stem cells. Furthermore, the chapter provides an overview of the currently used methods for isolating stem cells in adipose tissue, explaining the concept of point-of-care treatments with uncultured cells, and specifically comparing enzymatic and mechanical stem cell isolation techniques. It reviews Food and Drug Administration (FDA) regulations on human cell and tissue products (HCT/Ps), focusing on criteria for minimal manipulation and homologous use for these techniques. We also address the risks associated with “medical tourism” for stem cell treatments and the challenges orthopedic surgeons face when they want to use stem cell therapeutically. The strict regulations on stem cell therapies for professional athletes, emphasizing the guidelines from US Anti-Doping Agency (USADA) and the World Anti-Doping Agency (WADA) to prevent performance enhancement, are also discussed. Overall, this chapter provides a comprehensive overview of stem cell research by examining the theoretical foundations, current practices, and regulatory landscape, while discussing the challenges of using stem cells in clinical settings, aiming to guide clinicians in making informed decisions about their therapeutic use.