Silk was first discovered by the Chinese around 3000BC. From the very beginning, its main use has been in textiles, but there is some evidence of early warriors using it to sew up their battle wounds.

For centuries silk has been used for sutures because it is both very strong and compatible with the human body.

Now, Milton Park-based company Orthox is utilising those strengths, developing biomaterials to repair orthopaedic injuries.

Chief executive Dr Nick Skaer said: “Our materials have a huge range of applications, but right now, we’re focusing on the knee cartilage, the meniscus.”

The menisci — two per knee — are crescent-shaped pads of mainly collagen fibres.

Of all the joints in the body, the knee is the one that has to absorb the greatest shocks. Everyday occurrences, such as jumping down from a wall, place huge strains on our knees, while active sports like football or skiing compound that pressure yet further.

But while sporting injuries make the headlines, the majority of problems affect the man in the street.

The cartilage degenerates over time, leading to pain and inflammation. The answer is a partial menisectomy — keyhole surgery to remove the damaged tissue.

This relieves the symptoms, but the downside is that the patient is likely to develop osteoarthritis. Extracting the damaged cartilage leaves a hole or gap, thus heightening the pressure on the remaining tissue and leading to arthritis.

The body cannot regenerate tissue to fill the void and replacement knees at around £6,000 each are more common than hip replacements.

Silk has two sources — silk worms and spiders. Orthox’s technology is developing silk from the mulberry silk worm, one of a number of species of worm.

A month after hatching, the worm will spin a cocoon to protect itself during metamorphosis to a moth. That cocoon, around the size of a quail’s egg, contains a filament between 600 metres and a kilometre long.

Silk producers unravel and wind the filament, either singly or in multiples, depending on the strength required. Silk skeins sell wholesale at about £20 per kilo — expensive in terms of cloth, but cheap for medical applications.

Orthox buys skeins, then dissolves them in a process which keeps the silk’s inherent properties intact.

Dr Skaer explained: “What we’re doing is to take the silk back to the state it was in prior to being spun out of the worm, a liquid known as fibroin or silk dope.”

Using a patented and highly secret process, the fibroin becomes a tissue scaffold, an incredibly strong, resilient and porous structure. The fibroin is put though a sequence that mimics the silk worm’s spinning technique.

It involves pressure and chemical reactions to produce a fibre. This fibre incorporates technology gained from research into spiders’ webs to ensure that the fibres align in the greatest degree of order, hence its trademark name of Spidrex.

Inserted in a meniscal cavity, it supports the knee and absorbs blood and cells to completely regenerate the tissue in the void.

The silk is degenerated by enzymes in the body and completely dissolves in two to three years. Each such operation will cost about £1,000.

For knee cartilage, the scaffold is a small cylinder, a fraction smaller than a rubber on the end of a pencil. The cylinder can be trimmed and shaped as necessary. Held between finger and thumb and compressed, it feels tough and springs immediately back to shape.

Spidrex’s unique selling proposition lies in its mechanical toughness. Other products on the market, such as collagen and polyurethane, can absorb new cells, but fail to provide the vital support during tissue repair.

In a comparative test, Spidrex exhibited little change after three million compressions: a collagen-based rival failed after 100,000 cycles.

The scaffold is easy to insert and suture into place, which makes it simple for surgeons to adapt to the new technology.

Dr Skaer said: “That’s important. Allowing clinicians to use familiar techniques helps immeasurably with the transition.”

Also key is that with the cartilage fully supported, rehabilitation can be shorter and more aggressive. A joint like the knee is built to take pressure. Use a softly-softly technique for rehabilitation and the joint will respond to this easy life by ending up with less strength.

Orthox can be described as a spinout of a spinout (excuse the pun) based on the researches of Oxford University’s Professor Fritz Vollrath and Dr David Knight into silk, spider silk and bone repair material.

The company has just won a prestigious £1.6m grant from the Wellcome Trust and is seeking further backing of £2m in the next year.

Active collaborations are ongoing with the universities of Ulm and Heidelberg in Germany, and Northwick Park Hospital in Harrow. Clinical trials are scheduled for 2011.

Initial production of materials will be at the company’s new premises at Milton Park.

“The potential market for both Spidrex and our bone repair material is huge,” said Dr Skaer.

“As we scale up production for the meniscus, we’ll be looking at repairs for other vulnerable joints, too.”

Name: Orthox Established: 2008 Chief executive: Dr Nick Skaer Number of staff: Six Annual turnover: Confidential Contact: 01235 232111 Web: