Four Million Americans Have Bionic Knees

Four Million Americans Have Bionic Knees. That’s at least one in 20 people over 50 who has an artificial knee, thanks in part to both the nation’s obesity epidemic and its weekend warriors who keep on truckin’ past their prime. What’s more, younger age groups are starting to close the knee surgery statistical gap, which scares the heck out of doctors who foresee multiple knee replacements in longer-lived individuals who may start wearing them out at a faster rate. [Boston.com]