Osteoarthritis is one of the most common rheumatic diseases nowadays. This degenerative disease with a chronic and progressive course affects the elderly population. The diagnosis of osteoarthritis of the knee is made on the basis of a patient's subjective symptoms and objective clinical findings. However, the definitive diagnosis is established based on a radiological examination of the knee. The treatment of knee osteoarthritis can be pharmacological and non-pharmacological. Non-pharmacological treatment includes conservative and surgical methods. Non-pharmacological conservative treatment implies a change in a patient's lifestyle and adequate physical therapy. The surgical treatment of knee osteoarthritis includes palliative arthroscopic and classical surgical procedures. For the advanced cases of osteoarthritis that are resistant to conservative therapy, endoprosthesis and arthrodesis procedures are more suitable. Physical therapy remains the gold standard in the treatment of knee osteoarthritis. Physical therapies can be active or passive methods. Active methods of physical therapy include kinesiotherapy and hydrotherapy, while ultrasound, cryomassage and all other electrotherapeutic modalities belong to passive methods of physical therapy.