Rheumatoid arthritis is caused by inflammation of the tissues surrounding joints, leading to their progressive deterioration.
It extreme cases it can even kill patients by causing major organ failure.
The drug, Remicade, which has been approved for UK use, is a type of drug known as a TNF blocker.
It works by switching off the chemical TNF, or tumour necrosis factor, that stimulates cells to produce the inflammation response that leads to pain and swelling of the joints.
Clinical trials have shown that the drugs are very effective, but they cost around ten times as much as older treatments - up to £10,000 a year.
There are fears that not every patient who needs them will get them.
Professor Paul Bacon, of the Arthritis Research Campaign, said: "If you switch off the inflammation then you switch off the progressive joint damage that causes the disability in arthritis, and it also makes patients feel better.
"It is not a cure, but the joints do recover because you have turned off the inflammation."
Clinical evidence
Professor Bacon said the new drugs had been shown to work over a period of years.
He said they could be used in combination with older drugs.
The drugs were made available in the UK at the beginning of June, and health authorities are currently in discussion about whether are affordable.
Professor Bacon said the new drugs were expensive, but could save money in the longer term.
"Arthritis costs £1.3bn a year to the country. A lot of that is time off work."
Traditional treatments for rheumatoid arthritis, such as methotrexate and corticosteroids, have a high failure rate.
Some patients have to try a long line of therapies that may not work.
Professor Paul Emery, of the Arthritis Research Campaign, said: "The patients' quality of life is the real proof that this drug is a major advance.
"My patients who have been infused with Remicade really have had their lives changed. They can now do so many things that they haven't been able to do for years."
Rheumatoid arthritis normally strikes between the ages of 30 and 40, although children and young adults can be struck down.
Approximately one per cent of the population suffers from the disease, and about half of these will be too disabled to work ten years after diagnosis.