A painful form of arthritis in the foot affects one in six people over 50 - more than previously thought, research suggests.

Experts at Keele University's Arthritis Research UK Primary Care Centre studied more than 5000 people with painful foot osteoarthritis.

The condition is caused by inflammation in and around the joints, damage to cartilage and swelling. People can suffer a range of symptoms including pain, stiffness and difficulty moving, and often have osteoarthritis in other joints, such as hips or knees.

The study found that foot osteoarthritis affected more women than men, while those who have spent a lot of time in manual work are more likely to develop it.

Three-quarters of people with the condition reported having difficulty with simple day-to-day activities such as walking, standing, housework and shopping.

Dr Edward Roddy, clinical senior lecturer in rheumatology at Keele University, said the research had focussed on "midfoot" joints, which previous studies had neglected to do. He said a "substantial proportion of people" with painful foot osteoarthritis have the problem in this area, meaning there has been a previous underestimate in how common it is.

He added: "Foot osteoarthritis is a more common and disabling problem than we previously thought, making everyday tasks difficult and painful for people affected."

According to Arthritis Research UK, 7% of people aged 45 and over have sought treatment for osteoarthritis in the foot or ankle, including 9% of those aged 75 and over.