A new study has suggested a breakthrough in understanding how rheumatoid arthritis can spread around the body.

Researchers based in Bad Nauheim, Germany, found that cells surrounding joints affected by arthritis carry the condition to other parts of the body by travelling through blood vessels.

Published in Nature Medicine, their study indicates that cells known as synovial fibroblasts are responsible for spreading rheumatoid arthritis.

The researchers implanted healthy cartilage tissue and fibroblasts from people affected by rheumatoid arthritis into one flank of a group of lab mice, while the other side was injected with cartilage without the diseased cells.

After 60 days, they found that the fibroblasts had moved from one side of each mouse's body to the other and were causing cartilage damage.

Commenting on the study, microbiologist James Woods told Science magazine that it could represent "a critical first step" in finding a permanent cure for rheumatoid arthritis.

Until that happens, ultrasound can provide a way to reduce pain and promote healing for arthritis sufferers.