Electronic knee implants could help overcome arthritis

Millions of arthritis patients could be helped with electronic knee implants that encourage cartilage in the joint to regrow. According to bioengineers at the University of Connecticut, implanting a small mesh device into the knee produces an electrical current when it detects pressure, promoting cells to colonise it.

The device is just half a millimetre thick and generates piezoelectricity in response to regular joint movement. Arthritis is a common disease and is often worse as a person ages when the cartilage cushions between joints wear away.

It means bone rubs against bone, making many movements painful and everyday activities like walking can become very difficult. In turn, this can lead to a less active lifestyle and other health problems or simply a lack of independence.

Osteoarthritis is the most common form of the condition in the UK and there are some nine million people living with it. If the technology was to pass clinical trials, then it could spell hope to help relieve the pain and promote greater movement for these individuals.

At present, the most effective treatment is to replace damaged cartilage with healthy samples taken from elsewhere in the body or from a donor. This comes with risks, such as undermining the area where the cartilage is transplanted from or your immune system rejecting the piece from another person.

In the past, researchers have tried to get the body to grow more cartilage by amping up chemical growth factors, but this approach has had limited success. Bioengineered scaffolds to create a template for fresh tissue have not worked either.

The newest technique involves a tissue scaffold constructed of nanofibers of poly-L lactic acid (PLLA), which is a biodegradable polymer used to stitch up surgical wounds. Piezoelectricity occurs when it is squeezed, which happens naturally during walking.

Dr Yang Liu, lead author of the study at the University of Connecticut, said: “Piezoelectricity is a phenomenon that also exists in the human body. Bone, cartilage, collagen, DNA and various proteins have a piezoelectric response.”

No outside growth factors or stem cells are required in conjunction with the electronic implant, cutting down the chances of side effects. The cartilage that is stimulated to grow is also mechanically robust, which has not been achieved through other artificial methods.

Osteoarthritis most commonly starts to develop in people in their mid-40s or older and there are more cases in women than men. Often, individuals suffering from the painful condition have a history of it within their family.

While the new piezoelectricity therapy will need to go through years of trials, it represents an interesting new approach to tackling osteoarthritis. In the meantime, sufferers are forced to manage the condition as damage to the joints is irreversible.