The number of people with knee arthritis has exploded since I was a kid. One of the ways we can find out if this is related to our modern, industrialized societies is by looking at the bones of our ancestors. Even though they had far more wear and tear because being active was needed to maintain life, did that cause knee arthritis to be commonplace, or is it more common now in our relatively cushy world?
Bone-on-Bone Knee Arthritis
Bone-on-bone knee arthritis means the protective cartilage has completely worn down, and the joint space between the two knee bones (distal femur and proximal tibia) has narrowed to the point where bone is touching bone. When no cartilage remains, this would be considered severe knee arthritis, and this is what researchers focused on in the study below.
Study Compares Modern and Ancient Knees
In the new study, 2,600 skeletons from as recently as 2015 and all the way back to 300–6,000 years ago were investigated. All skeletal remains were estimated to be from individuals who were age 50 and older. The remains were each placed into one of three groups: death 1976–2015, death 1905–1940, and Native American remains from 6000–300 BP (about 4000 BC to 1700 AD). Investigators looked for a specific finding that indicated the subjects, while living, had that bone-on-bone contact at the knee. Knee arthritis was determined based on the ivory-like polish on the bones—when the polish is present, this is called eburnated bone, and eburnation occurs in bone-on-bone contact.
The results were quite telling. Bone-on-bone knee arthritis was present in 16% of the most modern group (the 1976–2015 group). The group just prior to the mid-20th century (1905–1940) had the fewest subjects with knee arthritis, at just 6%, while the most ancient group came in at 8%. So what has happened in recent decades to cause our risks for knee arthritis to more than double, and can that answer help us avoid knee arthritis?
Let’s take a look at some possibilities.
What Else Could Be Increasing Our Risk for Knee Arthritis?
With more than half of knee arthritis patients in the U.S. being under the age of 65, and the study comparing skeleton groups in the same age category, clearly aging can’t fully explain the prevalence of knee arthritis today. Body mass index (BMI) variables were also accounted for in the study, so obesity by itself also can’t explain knee arthritis, though digging into the risk factors for obesity (see metabolic syndrome below) may give us a clue. Additionally, we also can’t completely chalk it up to genetics as our mid-20th-century relatives’ risk for knee arthritis was less than half of what ours is today.
There are many other lifestyle changes and medical “advances,” however, that have occurred in recent generations that studies have shown may be factors in the skyrocketing increase risk for knee arthritis and in knee arthritis diagnoses in the past six-plus decades. Let’s review.
Hypertension: A recent study suggested that the presence of hypertension may be a risk factor for knee arthritis.
Metabolic syndrome: High blood pressure, early diabetes, and, yes, obesity are all indicators of metabolic syndrome, and it is prevalent in the American lifestyle today. The presence of metabolic syndrome has been shown to have an effect on cartilage by destabilizing its chemical matrix (its structure). increasing the risk for knee arthritis.
The low-fat, high-carb diet: The low-fat movement based on flawed science was off and running in 1956 when the American Heart Association recommended it on national TV. We now know a low fat, high-carb diet feeds metabolic syndrome and other diseases.
Sedentary lifestyle: Certain forms of exercise have been shown to not only keep joints healthy but also be beneficial when knee arthritis already exists.
Nonsteroidal anti-inflammatory drugs (NSAIDs): In the U.S., we are heavy consumers of NSAIDs (e.g., Aleve, Celebrex, Advil), despite the dangerous risks, for even the most minor pain and inflammation. Yet, NSAIDs have been shown to progress arthritis, making it worse over time, and in many cases, NSAIDs may not actually work that well for pain.
Steroid injections: Steroid injections are a significant risk factor for knee arthritis as steroids have a deadly effect on cartilage, and studies have also shown them to be ineffective at continuing to relieve pain.
The upshot? Looks like based on the results of this study, our modern world is harder on our joints than the world of our ancestors. That in and of itself is interesting as the ancient world was mighty physically rough on joints. However, sitting all day, eating processed high-glycemic foods, medications, steroid shots, and our modern surgery-happy insurance system seems to be even rougher!