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What is chronic pain?

Chronic pain is pain that is ongoing, keeps returning, or lasts longer than the normal course of healing. It can last long after the injury or illness that first caused it is gone. Chronic pain can last from several months to many years. It has a negative effect on a person’s well-being and ability to perform everyday activities.

What causes chronic pain?

There are many possible causes of chronic pain. According to the Institute for Clinical Systems Improvement, chronic pain can be grouped into four main types.

  • Neuropathic (nerve-related) pain: This is pain caused by damage to or malfunctioning of the somatosensory system. This is the system made up of sensory receptors and neurons (nerve cells) in the central nervous system and the peripheral nervous system (outside of the central nervous system). One example of neuropathic pain is sciatica (pain in the back, hip, and upper thigh related to the sciatic nerve).
  • Muscle pain: Problems with the skeleton’s muscles are a frequent cause of chronic pain. Myofascial pain (muscle tissue pain) can affect areas such as the lower back, hips, legs and feet, neck, shoulders, arms, and trunk of the body. It often occurs after an injury or following repetitive motions.
  • Inflammatory pain: Inflammatory agents trigger main sensory nerves that send pain signals to the spinal cord. Causes include arthritis, tissue injury, or infection. It may also be due to conditions that occur after surgery. Symptoms may include redness, warmth, and swelling at the site of the pain.
  • Mechanical/compressive pain: Mechanical pressure or stretching activates nerve cells that are sensitive to pain. Causes may include fractures, disc degeneration, or compression of tissue by tumors, cysts, or bony structures.

A person may have multiple conditions that cause chronic pain (for example, cancer and osteoarthritis).

In some cases, people have chronic pain when there is no apparent underlying cause that can be found. This is known as psychogenic pain. Psychogenic pain does not mean that a person is “making it up” or “crazy.” The pain is very real. However, psychological factors such as anxiety, depression, excessive stress, or environmental factors are the major explanations for this type of chronic pain.

Other types of chronic pain with no apparent cause may result from changes in the central nervous system. Sometimes after a disease or injury occurs, the central and peripheral nervous systems undergo abnormal changes in their structure and function. These changes may make people extra-sensitive to pain and may produce sensations of pain well after the injuries are healed. These dysfunctional changes in the central nervous system are known as central sensitization. Once the central nervous system has become hypersensitive to pain, it is difficult to reverse the hyperactivity and the associated persistent pain.