In Japan, most of the osteoarthritis of the hip is secondary due to congenital dislocation of the hip or acetabular dysplasia. Total hip arthroplasty is generally performed as the operative method for treating hip osteoarthritis, but conservative operative methods are recommended for younger patients. Joint congruity is judged good for the hip joint in which the joint surface of the femoral head is parallel to the acetabular joint surface. In the case of an incongruent hip joint, the load concentrates and becomes larger per unit area of the joint. Joint incongruence is found in the early or advanced stage of the hip osteoarthritis. The femoral osteotomy should be performed when joint congruity is improved in the hip abduction or adduction position. Walking exercise begins 2 or 3 days postoperatively, and passive motion exercise is performed as soon as possible. Weight bearing on the operated hip should be limited for the protection of the joint cartilage. In the case of preserving joint space preoperatively, walking with a single crutch is allowed 2 or 3 months after the operation. If there was no or only a narrow joint space before the operation, it is recommended that two crutches be retained for 6 months and that one crutch then be used for another 6 months. Good results in clinical and radiological findings are maintained in 80% or more 10 years after the operation.

Angles of the shoulder joint are usually defined in each of the sagittal, coronal, and horizontal planes passing through the center of the shoulder joint. One of the problems with this method is the difficulty of describing some positions of the shoulder joint such as the anterolaterally elevated position. In 2005, the International Society of Biomechanics proposed a recommendation on definitions of joint coordinate systems including the shoulder based on Euler/Cardan angles, which have often been used for the purpose of research on shoulder joint movement in daily activities. With this definition, however, it still remains impossible to define the angle of axial rotation in the hanging down position. Also, Codman's paradox, the phenomenon where the rotation angle of the shoulder changes after motions without axial rotation of the arm, remains unsolved. To solve these problems, a new method to define the angle of shoulder axial rotation, the non-singular method, has been proposed. This review describes the history and the problems of the methods used to define shoulder angles, and presents this new method of definition.