Those neurological changes include something researchers call plasticity. The neurons and pain receptors involved in the pain pathway – the channel from the source of the pain up through the spinal cord to the brain – actually change over time due to the nonstop pain signals caused by arthritis. It’s almost like a car alarm that won’t stop ringing throughout the night. Injury, inflammation and disease can trigger plasticity, and plasticity in turn can limit the body’s ability to turn off the pain response.

Pain that lasts for months or years, affecting a person daily or even just regularly, has a negative emotional impact, says Dr. Taylor. In addition, the persistent pain associated with arthritis can limit your ability to work, or do ordinary tasks like clean your house, dress or drive a car. Chronic pain’s impact on your life can be wide-reaching and devastating, he says.

Classifying Pain By Its Causes

The second means of classifying pain is by cause. There are three main categories:

Nociceptive: Wherever injury, inflammation or illness strikes the body, nerves in that area sense a problem and respond by stimulating the production of pain receptors called nociceptors. The nociceptors, in turn, stimulate special chemicals that travel up the spinal cord and to the brain. These chemicals are like a signal to the brain, triggering a general alarm that we feel as pain. This alarm tells you there’s something wrong. So although the inflammation or injury may exist in the finger, back or knee, pain actually happens in the brain.

Nociceptive pain includes somatic pain, caused by injury to joints, bones, muscles, skin or connective tissues like ligaments and tendons, and visceral pain, caused by injuries to internal organs like the gall bladder or liver, or tissues that support these organs.

Neuropathic: This type of pain is caused by changes in the nervous system, and it doesn’t subside even after the original injury or inflammation heals. Sometimes, an injury to the nerves can trigger this type of ongoing pain, or it can be associated with diseases like diabetes or shingles.

Psychogenic: While living with chronic pain can trigger or worsen psychological problems like depression or anxiety, psychological issues can also be the source of pain. Sometimes, when doctors can’t identify any physical injury or illness that may be causing persistent pain, they conclude that psychological problems may be the source. Whether or not this is the case, managing psychological factors like mood can help people fight chronic pain more effectively.

Researching the Pain Process

In recent years, scientists have identified which protein molecules are involved in the pain signaling process, and how the brain experiences pain. The goal is to gain a deeper understanding of the pain process and develop better pain-fighting treatments.

One important research development in the last few years was the discovery of vanilloid receptors, proteins involved in the pain process that cause the brain to sense dangerous levels of heat, particularly in areas of inflammation. Researchers hope that being able to identify more molecules involved in pain sensation may allow them to develop more targeted drugs to lessen the brain’s pain response to these stimuli.

In addition, researchers are looking at the genes that may contribute to some types of chronic pain. In 2011, British scientists at Cambridge University identified a gene, called HCN2, which is related to the nervous system’s regulation of chronic pain. This discovery may help doctors develop drug treatments that might block the pain-triggering proteins the gene produces, helping patients with nerve-related pain.