Knee OA More Common Now Than at Any Time in the Last 6,000 Years

A team of researchers from the United States and Finland has found that rates ofknee osteoarthritis (OA)are higher now than in the past – probably not for the reasons you think.

In a study published in theProceedings of the National Academy of Sciences, the researchers report that knee OA is more than twice as common today, in the post-industrial era, as it was at any time before, going back to prehistoric days. People in the 21st century are also more likely to have arthritis in both knees than were people in the past.

那么，研究人员是如何研究生活在几百甚至几千年前的人的关节炎的呢?研究报告的合著者、哈佛大学人类进化生物学教授丹尼尔·利伯曼博士表示，他们研究了博物馆里或捐赠给医学研究的50岁以上的人的骨骼。研究人员总共检查了来自美国各地的2576具骨骼。最古老的骸骨来自于6000年前的狩猎采集者;最近的是1976年至2015年间死于田纳西州和新墨西哥州的人。They also examined the skeletons of farmers who died 300 to 800 years ago and the skeletons of people who died in the early 20^thcentury.

The researchers say this big historical perspective was important because it allowed them to study known risk factors, especially age andobesity, under various conditions. Some experts believe the high percentage ofpeople who have OA目前，这是由于高肥胖率和较长的预期寿命，这创造了更多的机会，磨损关节。所以研究小组想要特别研究这些因素。

While just 1 percent of hunter-gatherers were obese – compared to 25 percent of people today – their knees took a beating because they were always on the move, picking berries and chasing down game. For that reason, the researchers assumed they’d find a lot of OA in our early ancestors as well as in industrial-age workers (1905-1940), who tended to have physically demanding jobs.

But they didn’t. When the researchers took age and weight out of the equation, they still found that 21st century humans had double the rate of OA of their forebears: Only 8 percent of early humans and 6 percent of 20^thcentury workers showed evidence of OA, compared to 16 percent of Americans today.

Lieberman says that means other factors must be driving the increase, but his team didn’t explore what those might be. Their best guess, though, is lack ofphysical activity. Lieberman points out that the biggest shift between now and even a few decades ago is that adults and children have become extremely sedentary, which can affect joint health. The lack of physical activity can lead to thinner, less resilient cartilage and weaker muscles that support and protect joints. If being sedentary is the culprit, then OA is almost entirely preventable, he and his colleagues note in the article.

纽约市威尔康奈尔医学院的助理教授、特殊外科医院的风湿病专家、医学博士Karmela Kim Chan也同意这一观点。

“There are many factors that a study like this wouldn’t be able to account for [like diet and injuries]. But it seems fair to assume that we in the post-industrial age are more sedentary than our pre-industrial counterparts. Modernity has made things much easier for us. But that also means we are no longer as active as we evolutionarily were meant to be,” she says.

Like Lieberman, Dr. Chan stresses that activity isgood for the knees and for jointsin general.

“There is good evidence that in patients with healthy knees, physical activity seems to slow down the development of arthritis. It’s very likely there are biomechanical reasons within the knee that explain this – that is, how cartilage and bone respond to the stimulation activity provides,” she explains. “In addition, exercise improves muscle strength, which probably makes arthritis less symptomatic.”

Dr. Chan recommends biking, either outdoors or on astationary bike, to help build up the quadriceps (the muscles on the front of the thigh that act as shock absorbers for the knee).

“If [you] don’t enjoy biking, then the elliptical or rowing machine are good proxies,” she says. “In patients with more advanced arthritis who find it difficult to stay upright for extended periods,exercising in the water是锻炼肌肉又不压迫关节的好方法。Evenwalking back and forth across the length of a pool有帮助。水不仅承载了病人的体重，还提供了阻力，[因此]肌肉更努力地工作。”

Author: Linda Rath for the Arthritis Foundation

Related Resources:

• Benefits of Exercise for Osteoarthritis
• Exercising with Osteoarthritis
• Tai Chi for Knee Osteoarthritis