Aside from primary arthrosis of the knee joint, injuries of the joint often play a role in the development of complex destruction, which cannot, or only unsatisfactorily, be treated with conservative therapy. The most common changes relate to the menisci, which require treatment as a result of injuries as well as due to degenerative changes. Aside from this damages to the ligament system with resulting cartilage defects are very common. Post-traumatic damages, such as tibial plateau fractures, even when surgically treated, often lead to arthrosis of the joint. The long-term treatment of both, German and international professional athletes and the routine gained in treatment of patients with primary and secondary arthrosis of the knee joint, based on the results of international studies, has led to a treatment algorithm that is adjusted to the individual needs and requirements of each patient.