A revolutionary single-shot jab that delivers DNA to cells could be a new way to tackle all types of chronic pain. The injection, which is now in clinical trials for conditions including osteoarthritis (wear and tear damage that means bones rub together), instructs cells to ramp up production of a key natural protein, IL-10, which has painkilling and anti-inflammatory properties. Chronic pain — where the pain lasts longer than 12 weeks despite treatment — affects around one in five adults. Despite decades of research, chronic pain is still poorly understood and hard to control. A survey by the American Academy of Pain Medicine found that treatment with painkilling prescription drugs helps about 58 per cent of patients on average.