Last month, I visited the Jaipur Foot clinic in New Delhi. You may have heard of the Jaipur Foot. It is both an invention — a prosthetic foot made from cheap materials costing about $45 (versus $8,000 for a similar device in the United States) — and an amazing, low-cost network of clinics around the world that has served more than 1.3 million people with new limbs, calipers and crutches.

I was expecting something like a hospital — saintly ladies bustling around in white uniforms, earnest doctors with stethoscopes, and, of course, hospital beds. Instead, I found a hole in the wall; it looked more like a place where mechanics strip down used motorbikes.

A group of people, some of them missing limbs, sat on a bench waiting to be served; others were limping or walking from one small room to another — from assessment to fitting to testing.