With Ram Chandra Sharma, he co-invented the "Jaipur foot", an inexpensive and flexible artificial limb, in 1969.
[1] The Jaipur foot is made of rubber and wood and is probably the lowest cost prosthetic limb available in the world.
The International Red Cross Committee has used it extensively in Afghanistan and other places to help amputees.
Sethi was recognized by the Guinness Book of World Records for helping a large number of amputees in obtaining mobility again.
The original idea of the Jaipur foot is supposed to have come to him serendipitously while he was riding a bicycle and had a flat tire.