Chronic pain is defined as pain that lasts longer than 3 months. Some experts define it as lasting longer than 6 months.
Chronic pain is different than acute pain in that it is not easy to find the cause. Diagnosis can reveal no injury in the body at all, and yet the patient can be experiencing very debilitating pain.
One way that chronic pain begins is from an injury. Scientists have found that repeated pain from an acute injury changes the way the brain lets you know you have pain. Even after the injury has healed, pain messages replay over and over again.