As the biggest synovial joint in the human body the knee is very important in carrying the body weight and for the motion. Beside its size, necessary to mention is, also, its complexity, because three bones are articulating in this joint: femur, tibia and fibula. In its biomechanics, except the movement of flexion and extension, rotation is, also possible with loosened collateral ligaments. As in the other joints the coverage of articular bodies is made out of hyaline cartilage which can be injured in trauma of different etiology. In the new era, orthopedic surgeons have recognized these types of injuries as the first stage of osteoarthritis of the knee and the importance of treating those, as well for the reduction of financial resources and, also for increasement of the quality of patient's lives. Today, some of methods for treating focal injuries of the knee cartilage are being used, but none of them completely fulfill the idealistic expectations of cartilage regeneration. Autologous chondrocyte implantation (ACI) is a newer method which has gained popularity and has shown promising results through past years. Despite of that, treating of this pathology still presents a great challenge for orthopedic surgeons, but with prosperity of new technology, surely new methods will be developed and the existing ones will be improved.