Got a few extra pounds? A little chronic knee pain? You're not alone. 61 million Americans suffer from knee pain (~20%) and over 200 million of us are more than just a few pounds overweight. Considering that every pound of extra weight increases the load on your knees from a step by about 4 pounds, that means 10 pounds weight loss can ease the stress on your knees from each step by 40 pounds!
When it comes to wear and tear on your knee joints, dropping excess pounds is huge. Most studies indicate that 7-10% body weight loss for overweight/obese individuals is the threshhold for significant reductions in knee pain and risk for osteoarthritis (OA).
But, brute force aside, extra pounds means extra inflammation. And here enters the paradigm shift in how we think about the pathogenesis of knee osteoarthritis and pain!
Long gone are the days when adipose tissue (fat) was thought to be an inert storage system for extra calories. We now know that fat is loud and proud when it comes to discussions with your immune system. Adipokines (molecules naturally secreted by fat cells) are a major contributor to chronic low-grade inflammation via communication with your immune cells.
But, what the heck does the immune system have to do with knee pain you ask conveniently for the purpose of this article? Pain is a multifaceted, complex and often controversial topic. Below is a simplified view on immune system involvement in knee pain...
Immune cells respond to injury via various (inflammatory) signals. These injury signals are generated with acute knee injuries as well as with wear and tear as we go about our daily activities. As cartilage and other tissues are damaged (osteoarthritis, OA), immune cells report to these areas to clean up debris from damaged tissue and initiate the healing process. As they do this, they often activate neurons responsible for transmitting pain signals or reduce these neurons' threshhold for transmitting pain signals... the result - more pain, less function.
While inflammation is crucial for the healing process, chronic low-grade inflammation signals these immune cells to be overactive in certain ways, increasing pain and damage at the injury site and delaying your return to normal function and activity. (Which is probably why we see benefit from curcumin, a powerful anti-inflammatory, for RA AND OA symptoms.) Thus, weight loss is not just a mechanical way of reducing knee pain and osteoarthritis risk, but very much a multi-systems approach.
Overweight women are 4x more likely to develop OA than women of a healthy weight. And for every 11 pounds lost, women may reduce their risk of OA by 50%!
Overweight men are 5x more likely to develop OA than men of a healthy weight. A man can reduce his risk of developing OA by over 20% each time he drops BMI categories (from 'obese' to 'overweight' and from 'overweight' to 'healthy').
When physical activity is made difficult with knee and joint pain, weight loss can become a challenge - but it's not by any means insurmountable. While there are tons of activities that you can do with achy knees to burn extra calories, and I never want to discount the benefical role that physical activity plays in health, well-being, and OA, you might consider this:
A meta-analysis of over 700 studies by Miller and colleagues found that weight lost through diet and exercise interventions over an average 4 month period was about 25 pounds. Weight lost with just exercise alone? A mere 6 pounds. Here's the kicker, though, weight lost through diet interventions alone: 23 pounds - no statistical difference between diet vs. diet + exercise. It's possible to lose weight and reduce knee pain and OA symptoms/risk with low activity. Is it more difficult? Yes. Will you lose some lean mass along the way if you're not including targeted, non-painful physical activity? Yes. But, you can do it. You just have to want it.
Concerned about knee pain or OA? Looking to start losing some extra pounds? There's a ton of considerations and places to start, which is why I have a job. But, my pro tip? Start with increasing your vegetable intake. This is where I see the easiest and biggest bang for the buck when it comes to weight loss, inflammation and general health. It's often easier to add things into your diet than to cut things out... and you'll find that when you add healthy things in, the bad stuff tends to disappear anyways. It's subtraction by addition. 5-7 servings of vegetables per day is a good target. You can always start small and work your way up. The increased fiber, vitamins and minerals, and phytonutrients you get will mean less calories into your system, better blood sugar control, and improved microbiome health and immune function.
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