Knee Osteoarthritis Twice as Common Today Compared to 75 Years Ago

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According to a recently published study in PT in Motion News, knee osteoarthritis (OA) has more than doubled among Americans since 1940. The authors of the study say that this increase is NOT due to the trends of having longer lifespans or a higher prevalence of obesity. Instead, it is thought that the cause of increased knee OA is primarily due to inactivity!  Here are some of the details:

In this study, knee joints of 2,756 skeletons of varying age were divided into 3 groups, as below:

  • Between 6,000 and 300 BCE (“prehistoric”)
  • 1800s and early 1900s (“early industrial”)
  • Late 1900s through the early 2000s (“postindustrial”)

The findings of knee OA in postindustrial skeletons was about 16%, while the early industrial group prevalence has a 6% incidence rate, and prehistoric sample is 8%. To determine whether or not heavier body weights contributed to this difference, the results were controlled by grouping skeletons according to Body Mass Index.  Even when compared with skeletons of similar body mass, the prevalence of knee OA remained two times higher for the postindustrial group compared to the group of early industrial aged skeletons.   Similar results held true when comparing skeletons of different ages.

Because age and body mass did not seem to have an effect on the instances of knee OA, researchers considered other differences between prehistoric, early industrial, and postindustrial lifestyles.  One of the major differences in postindustrial living is that the quantity of physical activity in a typical human day is significantly decreased.

Why are we more inactive?

The reasons for the general population becoming less active over time are multifactorial.  One large factor is that it is becoming easier to get what we want with the click of button on a computer or a smart phone, rather than requiring us to go out and walk around.  It has become more and more common to have food, groceries, clothes, and home apparel delivered to the home – limiting the quantity of community walking that we do to maintain our lifestyles.  Jobs have also changed greatly during the last 75 years.  Jobs have become less physically active and are instead more likely to involve working on a computer from a sedentary posture for 40 or more hours a week.

What can we do to reduce the risk of getting Osteoarthritis?

It can be difficult to get as much exercise as we need with a job that requires sitting or even standing at a computer all day. However, it is not impossible! If you have a job that requires working on your computer it is best to get a high low desk to be able to alternate between sitting and standing every 20-30 minutes. It is also important to take a break from work and take a quick stroll over to the bathroom or to get some water. This will keep you moving and will also help to refresh your brain when you return to the computer.  Although these are good strategies to use at the job, they do not take the place of a regular exercise program.  Finding other ways to incorporate physical activity into each day is important for your joints.

Here are some recommendations from the American College of Sports Medicine for how much cardiorespiratory, resistance training, and flexibility exercise we should be doing:

Cardiorespiratory Activity

  • At least 150 minutes of moderate-intensity exercise/week
  • 30-60 minutes of moderate-intensity exercise 5 days per week, or 20-60 minutes of vigorous-intensity exercise 3 days per week
  • It is OK to accomplish daily cardiorespiratory activity in multiple short intervals OR in one continuous interval. Shorter intervals should be at least 10 minutes in duration, however.

Resistance  Training

  • Train each major muscle group two-three days each week using a variety of exercises and equipment
  • 2-4 sets of each exercise is recommended. The repetitions for each set can vary based on your individual exercise goals.  Exercise that you can do comfortably for 8-12 repetitions build strength and power.  Slightly lighter resistance exercise that can comfortably be performed for 15-20 repetitions builds muscular endurance.
  • Resting for 48 hours between resistance training sessions is recommended.

Flexibility Exercise

  • Stretching to improve range of motion on 2-3 days/week is suggested.
  • A general guideline is to accomplish 2-4 stretches for 10-30 second holds

Does all of this advice sound daunting?

Remember that when it comes to physical activity, SOMETHING is better than NOTHING.  Even if you don’t think that you can meet the recommended exercise targets, it is better to move around in some capacity than to stay sedentary.  If you have questions or concerns about your ability to begin, update, or advance your individual exercise program, know that your Physical Therapist is an excellent resource.  The Symmetry team would be happy to help you to determine the best way to meet your specific activity needs.  Feel free to contact us if you would like to set up a consultation.

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