(Left) In this x-ray of a normal knee, the space between the bones indicates healthy cartilage (arrow). (Right) This x-ray of an arthritic knee shows severe loss of joint space and bone spurs (arrows)

(Left) In this x-ray of a normal knee, the space between the bones indicates healthy cartilage (arrow). (Right) This x-ray of an arthritic knee shows severe loss of joint space and bone spurs (arrows)

Original article and pictures take https://orthoinfo.aaos.org site