The articular cartilage of the knee is an integral part of the joint, providing a smooth, low-friction surface that allows motion and load transmission. Cartilage can be injured and ultimately wear out, leading to numerous clinical pathologies. This chapter describes the anatomy, biomechanics, and physiology of knee articular cartilage, emphasising the cellular structure, composition, and function of cartilage. Common cartilage injuries, diagnostic procedures, and workups are discussed, as are different imaging modalities, with an emphasis on magnetic resonance imaging. Therapeutic interventions for articular cartilage are described—including conservative management, microfracture, osteochondral grafting, and autologous chondrocyte implantation—and the potential and limitations of these interventions are emphasised. Rapidly evolving tissue engineering technologies, including scaffold design, are discussed in particular detail. Overall, the chapter emphasises the complexity of cartilage repair and the importance of patient-specific individualised clinical planning to optimise outcomes.