For the past four decades, many different avenues have been explored in efforts to repair and restore damaged cartilage zones in weightbearing zones, none more well-studied than the knee. Autologous Chondrocyte Implantation (ACI), which has gone through multiple "generations" of development, has held promise but produced inconsistent results. Microfracture is the classic surgical option, but is known to produce fibrocartilage which is of lesser quality than articular cartilage. In this study, the authors compared ACI to microfracture in patients with cartilage defects of the knee. They included 12 RCTs with 659 patients, and assessed pain, function, quality of life, and failure. While ACI outperformed microfracture in terms of activities of daily living, quality of life at five years, and pain at two years, the differences were small and inconsistent over time. Overall, there do not appear to be any definitive benefits of ACI over microfracture.