Joint Loading in Runners Does Not Initiate Knee Osteoarthritis.

Runners do not have a greater prevalence of knee osteoarthritis (OA) than nonrunners. The hypothesis that joint loads in running do not cause OA is forwarded. Two mechanisms are proposed: 1) cumulative load, which is surprisingly low in running, is more important for OA risk than peak load, and 2) running conditions cartilage to withstand the mechanical stresses of running.