Physically Active Children May Have Stronger Knees as Adults

Do you have children?

I have one, age three and a half. The way she uses (and abuses) her little body never ceases to amaze me. I sit and watch, without comment, as she takes part in marathon sessions of charging at the couch and slamming into the cushions.

One time she advanced across the rug, whipping her head violently back and forth, trying to induce dizziness. I recall thinking, “My God, my God -- your neck!”

Is she active? Do bears you-know-what in the woods?

If you have a similarly high-energy toddler, or older child, there’s good news. All that running and jumping about may be laying the foundation for stronger knees later in life.

That, anyway, is what a study of 298 Australians found. Subjects had their strength and fitness tested as children, then researchers did MRIs of their knees 25 years later. The findings, according to this summary article:

Childhood physical activity, including physical work capacity, leg and hand muscle strength, sit-ups, and long and short runs had a significant, consistent association with greater tibial bone area. In addition, higher childhood physical work capacity measures were associated with greater tibial cartilage area.

(The tibia, by the way, is the bone in your lower leg that meets the larger femur in the knee joint.)

Why this beneficial effect? One investigator in the study, Graeme Jones, speculates that it’s as simple as “bone area gets larger to cope with the extra demands put on it by higher levels of physical activity, and then this leads to more cartilage, as cartilage covers the surface of bone.”

Does this mean though that, if you’re an adult who spent his childhood watching cartoons instead of playing kickball, you’re out of luck now?

That seems highly unlikely to me. One thing that impressed me, after doing a lot of reading about knee cartilage while working toward my own recovery, was how dynamic the tissue is. It’s constantly changing -- sometimes for the worse, true, but often for the better too.

It has been shown that the knee cartilage of triathletes is thicker than normal. Is that because they were active as children? I very much doubt that. More probably, it’s because their present-day physical activity is busily modifying their cartilage in a lot of good ways.