The Relation of Running to Bone and Joint Disease

To the Editor.—  The recent investigations of a possible linkage between running and osteoarthritis of the knee reported by Lane et al¹ and Panush et al² are interesting and important. The studies are similar in that each compares avid runners with controls (mainly nonrunners) and arrives at the general conclusion that running is not associated with osteoarthritis of the knee.Both groups of authors consider the possibility that a selection bias might be present but either rationalize or dismiss it. Lane et al identify three possible self-selection biases: (1) resistance to osteoarthritis in runners, (2) osteoarthritis preventing running in nonrunners, and (3) early cessation of running in previous runners due to pain. They indicate that potential bias should be minimized because comparison of a group that runs a lot against a control group should exaggerate differences between the groups. Is it possible that they underestimated the magnitude and