The famous sheep has arthritis, which is a disease that damages bones and makes it uncomfortable to move.

Disease normally effects older animals

Arthritis is a disease that normally effects older animals but younger animals like Dolly, who is only five and a half years old, can also develop it.

The scientists who made her are now trying to find out if the disease happened because Dolly is cloned or if it would have happened anyway.

Animal welfare groups argue that Dolly's illness proves cloning is bad for animals and say scientists should stop trying to make animals in laboratories.

Cloning could help cure diseases

Scientists think that cloning animals could help people with diseases in the future, and want to continue to study Dolly and see what happens next.