Doctors are now clear that excess body weight triggers and aggravates joint inflammation.  We’ve learned there are at least two reasons for this:

1) Excess weight increases the force on the joints
2) Belly fat secretes inflammation chemicals that trigger damage within joints

This is disturbing, because so many people are overweight.  But it is also an exciting prospect, because it gives you an element of control—you have control over your own weight.  The evidence that losing weight reduces trauma, pain, inflammation within joints is now highly convincing and opens the door for a whole new approach to joint pain.  In general, weight loss seems to:

1) Help prevent the development of OA
2) Help the symptoms if you have OA
3) Slow the progression of OA

The effects of weight loss on the knee can be dramatic. For instance, if you lose one pound of weight, you reduce the force of the load on your knees by about 4,800 pounds for every one mile you walk.  If you lose ten pounds of weight, you reduce the force of the load on your knees by about 48,000 pounds for every mile you walk.

[INSERT GRAPHIC-BAR GRAPH COMPARING THE TWO FORCES]

Another way to view this question is to look at those who are at the most severe end of the spectrum and those who receive the most dramatic treatment—severely obese people who undergo stomach surgery.  In one study, obese people with OA had bariatric surgery, which resulted in an average weight loss of about 97 pounds (44 kg). Following the surgery, 89 percent of the patients had complete relief of pain caused by OA in at least one joint.

[Lementowski, PW, Zelicof, SB. Obesity and osteoarthritis. Am J Orthop 2008;37(3):148-51.]

This is a remarkable finding for people with osteoarthritis.  If weight loss can reduce joint pain in the most severely obese individuals, it truly raises the possibility that anyone can gain control over their painful joints.

Walk Your Way to Healthy Joints

Many studies have shown that simple activities like walking can reduce weight and body fat.  These studies have often used pedometers, which count the number of steps a person takes each day.  There is a general agreement that a good target number for steps is 10,000 per day.

A most recent study confirms this.  At the 2008 annual meeting of the Obesity Society, doctors from the Fred Hutchinson Cancer Institute found the following:

• Women who increased their activity level by an additional 3,500 steps a day lost 5 pounds during the year.

• Men who added at least 3,500 steps per day lost 8½ pounds in a year.

• The exercisers who did the most — 60 minutes, six days a week — decreased their belly fat by 10% to 20%.

• Those same exercisers trimmed 10% to 15% of their overall body fat without losing muscle mass.

Now, if we recall the negative effects of weight on the joints, this becomes very promising. Also consider the negative effects of belly fat on inflammatory molecules that affect the joints.  Such dramatic weight and belly fat reductions from walking (as found by the Frec Hutch researchers) would suggest that using the simple target of at least 10,000 steps per day could be the foundation for a joint health program with a high potential for success.

Beyond walking, here's some examples of the number of steps associated with various activities:

- 20 minute brisk walk = about 2,000 steps

- Low impact aerobics, 20 minutes = 2,500 steps

- 30 minutes of basketball = 4,300 steps

- 60 minutes of soccer = 10,000 steps

- Walking one city block = 200 steps

Weight loss reduces knee-joint loads in overweight and obese older adults with knee osteoarthritis.

Effects of exercise adherence on physical function among overweight older adults with knee osteoarthritis.