These shoes are rubbish. No, I'm not being rude. The yarn they are knitted from is made from recycled plastic bottles.

Who knew that the simple art of knitting would become the vortex where fashion, technology and sustainability would meet and change the way that clothes and, increasingly, shoes are made? Knit one, purl one... In the right hands, knitting patterns can easily become pixels and computer code, which is why it has become the new frontier in fashion and textile innovation.

Nike Flyknits have transformed Nike’s business and become as ubiquitous as blue jeans. In 2012, Nike introduced its first Flyknit shoe – a feather-light running shoe which moulded completely to the shape of your feet. In the four years since then, it has introduced almost 30 Flyknit designs, each tiny stitch can be designed and calculated.

This year it announced that it was using only recycled polyester yarn for the shoes, reducing manufacturing waste by over 1.5 million kilos and diverting 182 million bottles from landfill. And Adidas are all over the knitting machine too with their Primeknit technology creeping into everything from reinvented Stan Smiths to old school Superstars.

But if you are not someone who feels comfortable wearing sneakers off the sports pitch, check out the latest shoe knit sensation, Rothys. This San Francisco start up launched in June with simple but perfectly formed pumps (you can choose from pointy-toed or round-toed) made out of knitted recycled polyester yarn. They are super comfortable (I know, I spent the entire day walking round Kew Gardens in them this week) come in a variety of 17 colours and a few cool patterns like the grey khaki ones they sent me to try out.

The knitted upper moulds to your feet but – like the sporty versions – they are breathable, so it doesn’t feel like you are wearing sweaty plastic bottles; the insole is recyclable foam with a knitted footbed making them feel comfortable underfoot, and the sole is made from rubber. They are affordably priced (£95 or £110) and light enough to carry in your handbag if you need a spare pair of flats. Plus, I am told that you can throw them in the washing machine to be cleaned and they come out like new.

Rothys is the smart idea of Roth Martin, co-founder of Hedge gallery, which specialises in 20th and 21st century design, and Stephen Hawthornthwaite, whose background is finance. "The goal is that our shoes continue to be a chic, front of the closet solution for active lifestyles," says Martin. "Trends may be sprinkled in, as product extensions are a natural part of our growth plan, but the business foundation is less is more. Simplify."

Martin sees limitless potential for the shoes, not least because there is an excess of plastic bottles which are ground up, turned into fibre which is then knitted on a 3-D form so there are no uncomfortable seams and no waste. The knitting process takes just six minutes to make a fully formed upper. Currently they are manufactured in China because Martin was not able to set up the supply chain in America.

"We are team of ten with backgrounds in finance, design, tech and fashion all rooted in an ethos derived from SF origins – aesthetes, environmental consciousness, adventurers. Our programmers are machine and material experts who are willing to push the boundaries of conventional footwear to new limits,| says Martin.

Like the British knit innovators, Unmade, Martin sees the potential to knit shoes on demand so that they are never making unwanted products. At the moment they are producing shoes in two seasons, adding newness with colour and pattern. Once your old Rothys wear out you can send them back to be recycled while ordering a new pair by return of post. It’s the sort of thing you imagine could become a subscription service. Certainly, I am hooked on mine already. Now, where did I put my knitting needles?

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—Text by Tamsin Blanchard