OsteoarthritisOsteoarthritis (OA) is a degenerative joint disease which results in dysfunction and pain. Articular cartilage is a specialised connective tissue which is structurally important to the healthy functioning of articulated joints, and damage to this tissue can put individuals at increased riskRisks of developing OA. Autologous Chondrocyte ImplantationTreatmentAutologous Chondrocyte Implantation is a well-established cell therapyStem cell therapy for the treatment of cartilage defects in the knee, having been used for over 30 years. Other cell therapies exist that also target cartilage injury and the early stages of OA, including culture-expanded mesenchymal stem/stromal cell infusions, as well as a plethora of minimally manipulated cell therapy strategies. In this chapter in vitro and in vivo preclinical and clinical studies of these approaches are reviewed. The challenges of standardising and up-scaling manufacturing processes are discussed, in addition to the need for an improved understanding of the precise mechanisms of action of these interventions.