Chronic pain is pain that has continues for six months or longer, as a result of an acute pain condition that didn't fully heal itself, or due to neuropathic pain that continues to plague the peripheral nervous system.
Pain is a symptom of disease or injury. We experience pain when one or more sections of our body becomes injured, and the nerves of our body register changes in the area as a result of injury. The nerves that detect changes to body structures as a result of injury or disease may sense chemicals released by damaged cells/structures, or changes in temperature, pressure, or other mechanical changes to these structures. The nerves that permeate all of the body's tissues may respond to these chemical, thermal, or mechanical changes by sending pain signals to the spinal cord and brain. When the brain receives these pain signals, we may experience some level of pain. Though the transmission and interpretation of pain signals by the brain is a very complex process, here are some things we know. There are two types of pain and two levels of pain. The two types of pain are somatic pain and neuropathic pain. Somatic pain typically involves an injury to the soft tissues and other body structures affecting pain sensitive nerves in the scenario described above. In this typical scenario, the damaged structures or tissues begin sending information to the nerves until the injury has healed itself.
Cases involving somatic pain are typically associated with acute pain, assuming the injury heals itself in 6 months or less. Acute pain is pain that lasts from between a couple of days to up to six months. Chronic pain is pain lasting for six months or more. There may be several reasons why acute pain just doesn't go away. The first reason is due to orthopedic injuries that start out as acute pain injuries and turn into chronic pain injuries. A classic example of this type of condition is soft tissue injuries that never really after an accident or trauma. The soft tissues include joint cartilage as well as associated structures, such as ligaments and tendons. Ligaments and tendons both have structural components that allow them to be flexible as well as tough, and this flexibility allows them to shorten again after being stretched after an injury. Though these ligaments and tendons have the ability to reduce their length and return to their normal size, this ability does have limits, such as when they are repeatedly stretched or strained. Also, the flexibility in tendons and ligaments does decrease as we get older, hindering their ability to regenerate themselves. For the reasons mentioned above, people may never really recover from some types of soft tissue injuries, and we may continue to feel pain in these now unstable joints.
Many cases of chronic pain and chronic back pain involve direct damage to the nerve roots or nerve branches of the peripheral nervous system. The peripheral nervous system includes all of the nerve roots that exit the spinal cord and branch countless times as they innervate the entire body. In cases of neuropathic pain, the nerves become ill programmed to send pain signals to the brain in the absence of a real injury. With neuropathic pain, the nerves may start firing faulty signals because of a disease process that affects the peripheral nervous system, such as HIV infection, Multiple Sclerosis, shingles, or due to the side effects of spine surgery. Or chronic pain may begin as a result of an acute pain injury that initially causes pain sensitive nerves to fire appropriately before they eventually continue mis-firing pain signals long after the original injury has healed itself.