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An artificial foot designed for people who wear shoes and sit on chairs is of little use to a farmer who walks barefoot through muddy fields, squats to work and sits cross-legged at home. In Jaipur, the surgeon P. K. Sethi saw patients abandon imported limbs for exactly these reasons. This post covers how he and a local craftsman designed something better, the physics of standing on a foot, and what students can take from the story.
Who was P. K. Sethi?
The Ramon Magsaysay Award citation records that Pramod Karan Sethi was born in 1927 in Benares, now Varanasi, and studied medicine in India and Scotland. He joined the Sawai Man Singh Medical College and Hospital in Jaipur as a lecturer in surgery. In 1958 the hospital asked him to organise and head a new orthopaedic department, and the problems of amputees and polio patients became his concern.
Why did imported artificial feet fail Indian users?
The citation explains that amputation of a foot or leg often followed road, rail and factory accidents, or gangrene after snakebite among farmers who traditionally went barefoot. Artificial legs from industrialised countries were too expensive, hard to get and needed shoes. Even when people got them, they were often discarded "because users cannot sit cross-legged, squat or walk on uneven ground".
The design brief, then, was not "copy a good foreign limb". It was: build a foot for the way these patients actually live.
How was the Jaipur Foot made?
The citation describes the key step. Master craftsman Ram Chandra, using an old sand-casting method, made a die for a natural-looking foot that could be cast in any size. When large manufacturers would not help, the owner of a small tyre-retreading shop vulcanised a rubber foot in the die. After many trials, Sethi used a shell of this foot to enclose a new arrangement of components that allowed it to flex. It came in three skin tones, with a separation beside the big toe so that users could wear sandals.
The team described the design in a 1978 paper, Vulcanized rubber foot for lower limb amputees, in Prosthetics and Orthotics International. A 2008 article in the Journal of Bone and Joint Surgery summarises the result: the prosthesis "was cheap and could be made in one hour", and it let amputees work in muddy and wet fields and climb trees.
Worked example: why does a foot that flexes help?
Pressure is force divided by area, p = F / A. Take a person of mass 60 kg standing on one foot, so the force is 60 x 9.8 = 588 newtons.
If the foot stays flat on the ground with a contact area of 150 square centimetres (0.015 square metres), the pressure is 588 / 0.015 = 39,200 pascals, about 39 kilopascals.
If a stiff foot on uneven ground touches at only one small patch of 30 square centimetres (0.003 square metres), the pressure is 588 / 0.003 = 196,000 pascals, about 196 kilopascals.
Same person, five times the pressure, concentrated on one spot. These numbers are illustrative, but the principle is general: a foot that bends to keep contact spreads the load and grips better. A common mistake is to forget to convert square centimetres to square metres, which gives answers 10,000 times too small. Our guides to force and pressure and friction cover both ideas.
How did the work reach patients?
The new limbs were cheap but still beyond many patients. The citation records that in 1975 the Mahavir Society for the Physically Handicapped offered Sethi funds raised at a Jain religious festival. Endowments were set up so that each gift of Rs 2,500 earned enough interest every year to buy a limb and help with a train fare home. The number helped grew from 59 in 1975 to 2,035 in 1980, about 34 times as many in five years.
Engineers are still improving the design. A 2019 finite element study notes that the foot "suffers from an inconsistent lifespan" and found the interface between its rubber blocks a likely point of failure.
What did Sethi say the Jaipur Foot taught?
In his response to the 1981 award, published with the citation, Sethi played down the design itself: "It is not the technical virtuosity of its design features which excites me. Better designs will soon overrun it." What he valued was the method of working with craftsmen and patients. He concluded that "education should not be confused with institutional schooling, and that creativity is not a prerogative of the elite."
What can a student take from how he worked?
Write the real requirements. Squatting, sitting cross-legged and walking barefoot were the specification.
Learn from people with other skills. A sand-casting craftsman and a tyre shop solved problems that large firms would not.
Test, then improve. "After many trials" is how the citation describes the path to the final design.
When a pressure or friction problem keeps going wrong, the Fermi Problem Library has a step-by-step solver that explains the reasoning rather than printing an answer.
Today, measure the outline of your own foot on squared paper, estimate its area, and work out the pressure when you stand on one foot.
