The number of osteoarthritis cases in Britain is set to soar over the next 20 years.

Increased life expectancy and rising levels of obesity mean osteoarthritis cases are set to double to more than 17 million by 2030, charity Arthritis Care said.

The warning was made after a survey commissioned by the charity showed 71% of the UK's 8.5m osteoarthritis (OA) sufferers were in some form of constant pain and one in eight described the pain as often "unbearable".

Philip Conaghan, professor of musculoskeletal medicine at the University of Leeds, predicted millions more people would soon be affected by the joint-related illness because of an ageing population and a growing obesity problem.

"Britain is facing a tsunami of pain due to osteoarthritis as the number of people over 50 increases dramatically and obesity levels continue to rise," he said. "Action is needed immediately. We have to bust this myth that painful joints are an inevitable part of getting older we have to put up with."

The online survey of 2001 people with osteoarthritis, conducted between November and December last year, found the average age of diagnosis was 57 but one in five had been diagnosed under the age of 45.

People with osteoarthritis, which most commonly affects the hips, knees and hands, face £2.6 billion a year in extra costs as a result of paying for prescriptions, heating bills and transport costs, the research found. One in five has had to give up work because of their symptoms.

Of those questioned, 52% said they had given up or reduced walking since being diagnosed and 44% said they did no exercise at all, despite advice this is one of the best treatments for the illness.