The latest research indicates that knees might be tougher than commonly believed. They’re not just simple hinges; they play a vital role in supporting our weight and facilitating movement. Whether you want to stroll, climb stairs, engage in sports, or simply get up from your desk, you really need healthy knees. So, essentially, our future is tied to these essential joints.
However, there’s a lot of misunderstanding surrounding knee health. Jean-Francois Esculier, a physical therapist at the University of British Columbia, points out that opinions can be rather strong on what keeps knees healthy. For example, a study he led in 2022 involving 2,514 adults revealed that many people believe distance running increases the risk of developing knee arthritis. Yet, numerous studies suggest that runners generally face a lower risk and that their arthritis tends to develop more slowly, if at all. Indeed, running might even boost the health of knee cartilage.
Current science paints a more optimistic picture of knee resilience than many experts previously thought. With the right approach and a bit of luck, it seems our knees could stay robust throughout our lives. But aging does bring changes, and while some of these transformations are unavoidable, others may be manageable, suggesting we can influence our knee health.
What’s ahead is a science-informed guide about our knees as we grow older: insights into their function, how they change over time, and advice on how to protect them effectively.
Young knees
In your 20s and 30s, knees generally require minimal maintenance. Cartilage is typically at its thickest and healthiest, bones are strong, and tendons are intact. It’s not surprising that these are also the years when most people are most physically active—though research shows that our activity levels peak as toddlers and tend to decline thereafter. Regardless, physical activity is crucial for joint health during early adulthood, according to Keith Baar, an exercise scientist at McMaster University.
As we walk or move, our knees bend, causing bones to compress cartilage, which releases fluid. This process—cyclic loading—not only nourishes but also invigorates the cartilage. A 2024 study indicated that standing still for 30 minutes left knee cartilage almost flat, while walking for just 10 minutes allowed for a threefold faster recovery in cartilage health compared to being stationary.
That said, challenges emerge. Around age 30, muscle mass and strength start to decline, especially within the major leg muscles that stabilize the knees. Initially, there may be no noticeable change, but as muscle size reduces, the risk of injury and conditions like osteoarthritis increases. Sports injuries, particularly torn ACLs, are more prevalent in younger individuals, with nearly half facing early signs of arthritis a decade later.
Midlife knees
When we hit our 40s and 50s, knee troubles might start to surface, with the typical age for arthritis diagnosis being around 55, and cases increasing among those in their 40s. Studies show that knees can undergo concerning changes even if arthritis isn’t present. For instance, synovial fluid may diminish and become less viscous. Moreover, muscle strength, power, and mass tend to decline faster, accelerating joint instability. Sedentary lifestyles during midlife can see a loss of about 10% of strength and muscle mass every decade, which doesn’t bode well for knee health.
Excess weight during these years can also be problematic; many adults gain nearly a pound annually through midlife. This added weight adds stress to the knees and elevates bodily inflammation, both of which are potential factors in increasing arthritis risk. Movement often decreases as daily step counts for many hover around or below 5,500. This reduction in activity limits cyclic loading and negatively affects cartilage health.
The silver lining is that regular or increased exercise—especially resistance training—during this phase can provide significant knee protection. A 2024 study found that such activities reduced the chances of knee pain or arthritis by over 20% for individuals engaged in exercise before the age of 50. Even simple activities like walking can benefit knee health.
Older knees
As people enter their 60s and beyond, knee issues can escalate, with many undergoing replacements. Indeed, government statistics show that most knee replacement surgeries are performed on individuals around 66 years of age. Common joint problems often worsen, with research revealing that many older adults possess at least one meniscus tear, even if they don’t show any symptoms. Additionally, cartilage thinning typically accelerates, resulting in less cushioning between the femur and tibia, leading to the risk of bone-on-bone contact during movement.
Moreover, older knees generally have less synovial fluid, which also becomes thinner and less nutrient-rich. Muscle and strength deterioration quickens during these years, significantly affecting leg muscles critical for stabilizing the knee. Yet, while these changes can appear daunting, researchers suggest many of these issues are not a given. They can often be mitigated, especially through increased physical activity.
Simply walking more can enhance knee function and overall health. Research indicates that older individuals with knee arthritis who walked at least 6,000 steps daily maintained better mobility and experienced less discomfort compared to those who did not. On the other hand, even each additional thousand steps taken improved knee function significantly.
Exercises like squats, which target the quadriceps, can also help. In one study, older adults who engaged in squats over 12 weeks showed noticeable growth in muscular strength and an ability to rise faster from sitting—demonstrating the interplay between strong legs and healthy knees.
This article is part of a series on knee health, with the next installment focusing on advice from a knee doctor regarding the worst habits for sore knees.
