Experts say that is even though x-ray evidence of knee arthritis is not on the rise.
The study in the Annals of Internal Medicine finds, since the 1970s and 80s, the percentage of older Americans reporting chronic knee pain has risen three times higher than usual.
Knee replacement surgeries have skyrocketed over the past 26 years.
The nation's growing obesity problem and an aging population seemed to partly account for the increase in knee pain. One other reason, experts say, is that adults are more likely to admit having pain.