Changing Demographics in Osteoarthritis of the Knee

Peter L. Salgo, MD: Who is getting this, by the way? Are the demographics really changing when we look at this disease?

Paul Lachiewicz, MD: First of all, I just want to mention, unfortunately, this is a very common problem. It is estimated that somewhere between 52 million to 53 million people in the United States now have osteoarthritis of the knee.

Peter L. Salgo, MD: That’s about one-sixth of the American population.

Paul Lachiewicz, MD: Well, they actually say it’s 20% or more of the US population. About 13% of women and 10% of men over the age of 60 supposedly have symptoms of osteoarthritis. One of the things that I’ve noticed, and I’d like to hear from Rich on this, is that we’re seeing younger patients. In the past, the average patient was in their 60s. Now, coming into my office are both men and women in their 50s, or even their early 50s. And sometimes, they have advanced osteoarthritis. So, there is a change in demographics.

Peter L. Salgo, MD: Why is this?

Richard Iorio, MD: It’s interesting. I think we’ve had a sociological shift, in this country. We’re active for longer. We live longer. But, we’re also heavier. We have more incidence of obesity and diabetes than we ever had. That metabolic syndrome, or the group of diseases that causes diabetes and obesity, also leads to cartilage metabolism issues and leads toward accentuation of arthritis. If you put, on top of that, risk-seeking sports and higher levels of activity, that can also lead to it. The other issue is, we’re a very demanding culture. The baby-boomers want to feel good and want to feel good now. They want treatment for their disorders of their knee. So, we’re intervening with knee replacement and other surgical procedures earlier than we used to. The number of knee replacements has accelerated quite rapidly.

Andrew Spitzer, MD: I think you highlight 2 cohorts that I see in my practice. One is sort of the obese, inactive population that develops osteoarthritis, perhaps, from some biologic inflammatory reason. Then, there’s sort of the younger weekend warrior who really is pounding away at their knees. That’s perhaps a different mode of action of how we end up getting to this final common pathway. But, I think demographically, we’re certainly seeing that shift in the sense that the face of osteoarthritis is getting younger. In the decade of the 1990s, the mean onset was somewhere in the early 70s—70, 71, 72. In the decade of the 2010s, we’re seeing an onset somewhere around 60%, where of the new diagnoses of osteoarthritis are seen between the ages of 45 and 64. Whether it’s happening earlier, whether we’re diagnosing it earlier, and whether or not we have more tools to treat it is not clear to me. But, clearly, we’re seeing that younger face of osteoarthritis.

Peter L. Salgo, MD: You think back, in recorded history, to the riddle of this sphinx—it walks on 4 legs in the morning, and 2 legs in the afternoon, and 3 legs in the evening. It’s that 3 legs. It’s people who need a cane, or people who get joint pain. When you look at it in this context, people were getting osteoarthritis in ancient times. But, I look at folks. I have a little hobby. I see 40- and 50-year-old patients limping. I ask, “How many marathons have you run?” “Oh, I’m really healthy.” “Yes, but how many have you run?” It’s a lot. Is it cultural? We’re forcing our bodies to do something for which they’re not equipped?

Richard Iorio, MD: We have a conundrum, right? You want to stay active and fit, but you’re exercising for your heart. That’s the muscle you’re exercising for, right? Unfortunately, if you do high demand, high impact exercise, it’s not very advantageous to your knee. If you look at the current incidence of knee replacement, we just crossed the Rubicon. The number of knee replacements in patients younger than age 65 will outpace the number in patients over age 65. Whereas, not too long ago—25 years ago—it was very rare to do a knee replacement in people under the age of 65. Plus, the operation has improved greatly, too.

Transcript edited for clarity.