Stuff Matters: Exploring the Marvelous Materials That Shape Our Man-Made World

by Mark Miodownik

Next time you are sitting in a café with little to do but watch the world go by, have a look at how people walk. It is kneeled—meaning that you push your knee out ahead of you, positioning it above the point where you wish to plant your next step, allowing the lower leg and foot to swing into place underneath it. Once planted, the foot has to adjust its angle to the terrain, twisting or tilting it, both of which also involve complex knee adjustments and realignment. Running is even more stressful on the knee as it must do all this while being buffeted by repeated impacts. Try walking without bending your knees and you’ll see how important this joint is to mobility.