Here's one way to ensure having the best chance to avoid the bludgeoning numbers of folks having to a knee replacement.
Researchers at the University of Massachusetts Medical School tracked 9,000 patients in a first-of-its-kind database for knee and hip replacements and patient reported outcomes. They concluded that the increasing rate of knee replacements currently being performed could be linked to increasing obesity rates among younger patients.
Researchers stated that "55 percent of patients under age 65 were considered technically obese compared to 43 percent age 65 and older. Even more striking was that twice as many younger patients were in the morbidly obese category (body mass index greater than 40) – 11 percent of those under age 65 versus 5 percent age 65 and older. The younger patients also had higher rates of smoking and lower mental health scores." Read more about original study...
But of course we intuitively knew this already, didn't we? Carrying around more weight will wear out your joints faster, It is very simple.
Something you might not know is that body weight forces are multiplied by different types of activity. A Journal of Bio-mechcanics study (J Biomech. 2010 Aug 10;43(11):2164-73) determined peak forces as a percent of body weight for the following activities.
Peak Forces as a Percentage of Body Weight
Stair descending (346% BW)
Stair ascending (316% BW)
Level walking (261% BW)
One legged stance (259% BW)
Knee bending (253% BW)
Standing up (246% BW)
Sitting down (225% BW)
Two legged stance (107% BW)
See how high one legged standing is? All your body weight is being carried on one leg driving up the forces that your knee is experiencing. It makes sense then that descending stairs and ascending stairs are rated high as well because lowering on one leg and raising up on one leg are just more difficult versions of a one legged stance. This is by the way, one of the reasons why stair training is more difficult to master after someone gets their knee replaced. But I digress...
Negative Effects of Obesity
It makes sense that obesity at a younger age will predispose you to greater damage because you are generally still very active. You will be using up what is suppose to be a lifelong supply of cartilage. If on the other hand, you gained some extra pounds late in life after you had slowed down, you would not be in the position to do as much damage to yourself.
One the positive side, research from 2005, (Arthritis Rheum. 2005;52:2026-2032) found that for each pound of weight lost there was a fourfold reduction in the load exerted on the knee per step during daily activities. Just one pound of weight loss will help protect your knees into old age.
The four take home points to avoid a knee replacement are:
* Some activities are more demanding on your knees and wear them out faster
* Being overweight is more taxing on your knee no matter what activities you choose.
* Being overweight at a younger age is more damaging to your knees
* Just one pound of weight loss can ensure a fourfold reduction in knee forces.
So the moral of the story is...
Get started taking the weight off now or you may just have to get in line to have your knee replaced.