Objective: Patients with hip or knee osteoarthritis suffer from severe joint pain and have a decreased activity of daily living (ADL), but they usually do not apply for certification as physically disabled under the present circumstances in Japan. In addition, even if they apply for certification, they are unable to obtain sufficient support from the government because they are certificated as seventh (or sixth for bilateral hip or knee) physically disabled grade in many cases, which indicates a relatively low level of disability. In contrast, patients who undergo total hip or knee arthroplasty are certificated as fourth (or third) grade unconditionally, i.e., they are considered to have suffered complete loss of the use of one hip or knee, despite the fact that their pain and ADL are both improved after the treatment. We think that this certification is inappropriate, and herein make a suggestion for changing the Act on Welfare of Physically Disabled Persons. A before-after study design was developed and applied to patients who were treated with total hip or knee arthroplasty for osteoarthritis.<br>Methods: The clinical results of patients and the physically disabled grade system according to the Act were analyzed. Patients who were treated with primary total hip or knee arthroplasty for osteoarthritis were evaluated between April 2008 and March 2011 at Sanraku Hospital, Tokyo, Japan. A total of 31 hips in 28 patients [aged 67.0±8.3 years (mean±SD)] were treated with total hip arthroplasty (THA), and 31 knees in 27 patients (aged 74.0±6.8 years) were treated with total knee arthroplasty (TKA). The Japanese Orthopaedic Association hip and knee rating scores (JOA scores) were used to evaluate the joints when the patients entered and left the hospital. Patients were also asked about their pre- and postoperative certification grades as physically disabled. The physically disabled are supported by the Act, the Order for Enforcement of the Act, and the Ordinance for Enforcement of the Act. An Appended Table in the Act defines the scope of physically disabled patients who can receive certification. Appended Table no. 5 in the Ordinance contains the physically disabled grades and states how grades are assigned. The Ministry of Health, Labour and Welfare has produced several Notices about concrete definitions and certification. These Tables and Notices were examined for orthopedic disabilities of the hip and knee, including joint arthroplasty.<br>Results: Preoperatively, only 1 THA patient (3.6%) was certificated as having a third grade disability; postoperatively, 24 patients (85.7%) were certified as third (6 patients) or fourth (18) grade disabled. Therefore, 23 patients (82.1%) were newly certified postoperatively. The mean total JOA score of the affected 25 hips in the certified patients made a dramatic improvement from 52.1±11.6 (/100) to 81.5±7.5 (p < 0.01), and the means of all subscales also improved. Their certified grades were third or fourth level, even though their postoperative corresponding grades were sixth or seventh level (i.e., grades based only on clinical results, without reference to certification grades and total joint arthroplasty). None of the TKA patients was certificated preoperatively, but 20 patients (74.1%) were certified as third (11 patients) or fourth (9) grade disabled postoperatively. All of these 20 patients were newly certified postoperatively. The mean total JOA score of the 23 affected knees of the certified patients made a dramatic improvement from 58.9±11.1 (/100) to 74.6±9.4 (p < 0.001), and the means of all subscales also improved. The patients' certified grades were third or fourth, even though their postoperative corresponding grades were sixth or not applicable, similar to the THA patients. ...