Inclusion Criteria:  All adult outpatients, of both sexes, regardless of age, with a doctor-accepted diagnosis of knee OA and who have been treated with SV within the past 3 years  Exclusion Criteria:  Patients who have not been treated with SV in the past 3 years. Patients who have been treated with VS for an indication other than osteoarthritis of the knee. Patients in whom the assessment could not be performed reliably