Why do your knees ache going down stairs now when they never did at forty? Not sharp pain, but a low-level protest on steps, after sitting too long, or first thing in the morning.

It would be easy to file this under general aging and assume the cartilage is simply wearing out. But inside the knee, something more specific is happening, and menopause may have accelerated it.

Chondrocytes are the only living cells inside knee cartilage. They build and maintain the cushioning matrix of collagen fibers and water-trapping molecules that keeps the joint surface smooth and absorbs the force of every step.

Cartilage has no blood supply. Nutrients reach chondrocytes through diffusion from synovial fluid, aided by fluid pressed out and drawn back in each time the knee bends and straightens, like a sponge that must be squeezed to absorb.

With age, chondrocytes can enter a state called senescence: they stop repairing the matrix and begin releasing inflammatory molecules and enzymes that actively degrade it. A 2025 review in npj Women's Health found this shift accelerates in the years after menopause, once estrogen is no longer holding it in check.

Estrogen receptors sit directly on chondrocytes; animal and cell research shows estrogen helps keep these cells in their maintenance state. A 2025 study in Nature Aging found that menopause-related hormone loss increased senescence markers and cartilage breakdown in mice, consistent with clinical data showing knee osteoarthritis is nearly twice as common in women after menopause.

Direct evidence of estrogen's cartilage-protective role in humans is still emerging, though the pattern is consistent. If knee pain is persistent, severe or new, or if the joint locks or swells, have it evaluated to rule out meniscal tears or other conditions.

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Cartilage feeds itself through movement; every step compresses and releases the knee, cycling nutrients through a tissue that has no blood supply. Prolonged sitting holds it compressed and cuts off that exchange.

A network meta-analysis of 217 randomized trials, drawn mostly from mixed-sex populations, published in The BMJ found that low-impact aerobic exercise, particularly walking, cycling and swimming, was the most effective type for easing knee pain and improving function. A short daily walk keeps the compression-release cycle going and strengthens the muscles that stabilize the joint.

Partly true. Cartilage does thin with age and use, but research from Stanford published in Nature Medicine found that osteoarthritis involves active inflammatory processes driven by cells inside the joint, not just mechanical wearing.

The distinction matters because "wear and tear" implies the process is passive and inevitable. The evidence says it is driven by active biology, and factors like movement, muscle strength and hormonal status influence how fast it progresses.

Sit tall in a sturdy chair with your feet flat on the floor and your knees bent at a right angle.

Slowly straighten one leg until it is parallel with the floor, toes pointing toward the ceiling. Squeeze the front of the thigh and hold for five seconds.

Lower the leg slowly, taking three seconds to return the foot to the floor. Repeat eight times, then switch legs.

After both sides, bend and straighten each knee gently through its full comfortable range five times. Let the joint glide without holding at the top or bottom.

Your knee cartilage does not just wear thin with time. The cells inside it change after menopause, and the most direct thing you can do for the ones still working is keep the joint moving.