A metal bean that slips inside the knee to reduce the pain of arthritis and improve movement can be implanted by a surgeon in less than an hour. The device, which is shaped like a large kidney bean, has been engineered to fit exactly inside the knee in place of lost cartilage. It needs no screws, wires or cement.

Research shows the pain relief for patients as young as 39 who have been fitted with the device is as profound as that with knee replacement.

Knee arthritis is a growing problem.

Painkillers, physiotherapy and steroids are among the treatments available, but some people will eventually need partial or total knee replacements, when joints made of metal and plastic are implanted.

Each year, lakhs of knee replacements are carried out throughout the world.

During knee replacement, which can require a hospital stay of up to ten days followed by intensive rehabilitation and up to three months off work, a surgeon cuts

away damaged bone and cartilage from the knee and replaces it with an artificial joint made of metal alloys, plastics and polymers.

Because the ends of the bones are removed, the operation is irreversible.

Some research suggests a knee replacement lasts for at least ten years, after which a revision operation might be needed to replace it.

Revision operations are more complicated than original knee replacements and the results are not always as successful.

Knee replacement is usually carried out on older adults because younger, active people are more likely to wear out their new knee prematurely.

A new device A new treatment, developed by US-based Advanced Bio-Surfaces is a minimally invasive option for patients who have exhausted non surgical therapies.

One of the advantages of the new device is that its implantation does not rule out a future joint replacement, if necessary.

A knee joint has three parts: the thigh bone (femur), shin bone (tibia) and kneecap (patella). Where the bones meet, they are covered in a hard, slippery material called cartilage that helps them slide over each other easily.

Arthritis damages the surfaces where the three parts of your knee slide over each other. This hurts and stops your knee bending the way it should. It also makes your knee weak.

When cartilage is lost, the bone underneath can thicken and cause swelling. The implant is intended for use where a substantial amount of cartilage has been lost as a result of disease.

The knee implant from Advanced Bio-Surfaces is designed to replace missing cartilage.

Now approved for medical use in the US and Europe, the cobalt-chrome alloy device sits inside the joint on the top of the lower leg.

The device is implanted through a 2-3-inch cut made in the knee. It is slid into place after the knee compartments have been prepared by cleaning up the loose cartilage.

The device comes in various sizes, ranging up to 2-inches across. It has a lip at the back and a raised edge in the curve of the kidney bean shape. While the lip prevents it moving forwards, the ridge stops it going sideways.

"So far results have been very good." says Dr Jane White head of research at the company. "The first patients to have the implant experienced a 60 per cent drop in pain levels. We think the people who will benefit most long-term will be younger patients, because they will be able to delay that first total knee replacement, if they need one."