You specialize in the minimally invasive surgical treatment of knee ligament and cartilage injury, particularly in athletes. What are major methods of repair of cartilage defects in the knee? We have different methods to restore cartilage in the knee. Internationally we have an algorithm that helps to choose techniques for an arthroscopic method of knee cartilage repair. The arthroscopic method mostly will be used in a defect size of about 1.5 to 2 square centimeters. We have different methods of knee cartilage repair. The old surgical treatment techniques are marrow stimulation techniques. The idea is to create bridging between the pool of stem cells in the bone marrow and the internal space of the joint. We do this by perforation of the subchondral bone plate during the arthroscopy. We recruit the cells from the bone marrow, which has an enormous regeneration potential. And these stem cells are coming into the cartilage defect to restore the cartilage by transforming themselves into cartilage cells. So the stem cells change to different shapes and become chondrocytes. And chondrocytes become cartilage. So these are the sports injury cartilage repair steps inside the knee. There is a new repair technique that I use now. I avoid the classic microfracture with these instruments to damage the bone. So I use K-wire drilling to perforate subchondral bone. Because one of the problems with these microfracture techniques is bony edema or inflammation reaction in the subchondral bone. That creates pain and inhibits the return of the athlete to sport. So we have to be more careful in that cartilage injury treatment not to destroy the bone more than we need. The second point in knee cartilage defect repair is using Platelet-Rich Plasma (PRP). These are molecules or protein molecules which stimulate healing and coordinate the process of healing. So I combine the technique of K-wire drilling to open up on the subchondral bone plate. I combine surgical drilling with the patient’s Platelet-Rich Plasma (PRP). So we have two approaches to knee cartilage injury. One is that we recruit stem cells, the cells we need for all regeneration processes. We also use proteins that control the differentiation of cells and enhance the healing sequence of cartilage injury. So this combination of surgical and stem cell therapy generates a better outcome. Meanwhile, there are many matrix-associated techniques in combination with bone marrow stimulation techniques. So drilling is just one step to recruit the stem cells. Platelet-Rich Plasma (PRP) is used in the cartilage matrix. For example, chitosan gel could also be injected as a part of therapy to stimulate cartilage regeneration. Chitosan can improve the healing and enhance the quality of repaired cartilage tissue because one of the limitations of the bone marrow stimulation techniques is this. Without any additional factors like PRP or BST-CarGel, we only see a type of cartilage called fibrous cartilage. It is not high quality cartilage. Adding some other molecules like the Platelet-Rich Plasma (PRP), chitosan, or collagen helps the stem cells create a better cartilage quality. This is very important in the field of knee injury treatment for athletes.