Osteoarthritis of the knee is a condition in which pathological changes occur in the articular cartilage and with the progression of the disease it spreads to the surrounding structures. The degenerative process itself is most prevalent on loaded joints, more precisely the joints that are responsible for transmitting the greatest force during movement, among which is the knee. Research has shown that more and more people over the age of 65 suffer from degenerative changes. The course of osteoarthritis itself has not yet been sufficiently investigated, but some risk factors are known nonetheless. Accordingly, we divide them into primary and secondary. The primary cause is usually not sufficiently investigated, but is associated with aging, while secondary arthrosis is always preceded by a condition or, in most cases, by various biomechanical disorders that are the trigger for its occurrence. In addition to all conditions, it is stated that the patient's lifestyle itself is one of the risk factors. The first and most significant symptom is pain that occurs after certain movements or all-day exertion. As the disease progresses, symptoms become more frequent and stronger, movements in the joint itself are limited, swelling, crepitations and the development of secondary deformations in the joint itself occur. When diagnosing, important methods include clinical picture and X-ray findings, along with mandatory magnetic resonance imaging. The treatment is divided into conservative and operative. Conservative methods are medical treatment and physical therapy, by which we try to relieve the joint itself and teach the patient how to live with arthrosis. If conservative treatment did not give good results, palliative and causal treatment methods are used. Moreover, if none of the treatments mentioned before do not give any results, alloarthroplasty or joint arthrodesis are used. Regardless of the course of treatment, physiotherapy plays an important role, but before the actual application of therapy methods, it is important to make a detailed assessment using a subjective and objective examination. During the objective examination, we come in contact with the joint itself through inspection and palpation. It is important to assess muscle strength through a manual muscle test, measure the range of motion and measure the volume of the joint itself. Based on the received information, a further rehabilitation plan and program is created. The most important part of rehabilitation is the application of therapeutic exercises, which are complemented by the application of thermotherapy, electrotherapy and cryotherapy.