Articular cartilage injuries of the knee are common among active and athletic individuals, affecting up to 1 million patients per year and accounting for up to 200,000 surgical procedures per year. Originally published in our Journal of Knee Surgery, this collection of articles, are written as substantial book-like chapters reviewing current concepts on core topics of articular cartilage injury of the knee. Each is written by the absolute leader in the field and are incredibly up-to-date. Because articular cartilage lacks the natural ability to heal, treating cartilage problems poses a unique challenge to orthopedic surgeons. Restoring articular cartilage is essential to relieving pain and allowing better function of joints. Even more important, restoration can delay or prevent the onset of arthritis. These are NOT journal articles reporting on original research; they are expert authored concept reviews of a hot and contemporary topic in orthopedics. Each emphasizes a patient-based approach and includes "the science behind the surgery."