He's going to have his hip joint replaced.他准备接受髋关节置换。It may be that you are unaware of where your hip joint is; it is not at the waist but a good hand span below it.这也许是因为你并不晓得髋关节的位置，它不在腰部，而是位于腰部以下一手拃宽处。The hip joint is a ball-and-socket joint.髋关节属于球窝关节。