The affliction, caused by flexing the neck for extended periods of time, can be a forerunner of permanent arthritic damage if it goes without treatment. Cases of the repetitive strain injury are on the rise as smart phones and tablet computers such as the iPad become increasingly popular, experts said. In severe cases the muscles can eventually adapt to fit the flexed position, making it painful to straighten the neck out properly. One chiropractor said her company had treated thousands of patients for the condition, which can also result in headaches and shoulder, arm and wrist pain. Rachael Lancaster, of Freedom Back Clinics in Leeds, said: "Text neck is caused by the neck being flexed for a prolonged period of time