Osteoarthritis is the most common rheumatic disease and the most common cause of chronic physical disability. The knee joint is the most common localization of osteoarthritis. The disease affects the articular cartilage, all joint structures and soft tissues around the joint, and is a consequence of mechanical and biological events in the joint. The main symptoms of osteoarthritis that patients first notice are pain, stiffness, and decreased joint function. The diagnosis of the disease is made on the basis of anamnesis, clinical picture and radiological picture. Physiotherapy intervention in its procedures applies various tests and questionnaires to gain insight into the patient's condition and the progression of osteoarthritis. Treatment of osteoarthritis can be non-pharmacological, pharmacological and operative. From nonpharmacological procedures, physical therapy stands out, which, along with kinesitherapy, gives the best results. The use of pharmacological preparations depends on the current condition of the patient and the progression of the symptoms of the disease. The most widely used are paracetamol, topical preparations, nonsteroidal antirheumatic drugs, opioid analgesics, glucocorticoids and hyaluronic acid and its derivatives. When pharmacological preparations do not achieve results in treatment, they undergo arthroscopy, osteotomy and arthroplasty. The aim of the final paper is to explain in more detail the impact of osteoarthritis on the knee joint and its treatment.