Understanding pain – what it is and why we feel it

Article from Arthritis Today Spring 2016 - No 169

This issue we're looking at pain. Why? Because more than 1 in 6 people struggle with the pain of arthritis every day.

Pain may be a common symptom experienced by millions, but it's a deeply complex issue.

Why do we feel pain? What is it about arthritis that causes pain? Why can two people have the same amount of deterioration in the joint but feel completely different levels of pain? These are just some of the questions you’ve asked about pain which our experts have helped us to answer.

What is pain?

Put simply, pain is a protective mechanism that alerts your brain when damage has occurred. It’s not just a sensation, it has emotional effects too – often making us feel upset or distressed.

It can be caused by injury, by chemicals produced by inflammation or by damage to nerves or nerve endings. Pain can continue after the damage seems to have gone, so sometimes it’s difficult to identify the cause of long-term or chronic pain, which can make it tricky to treat effectively.

Professor Philip Conaghan, professor of musculoskeletal medicine at the University of Leeds, says:

"Any pain, however short-term, can have a negative impact on us, physically and emotionally.

"Because pain is invisible and our experience of it is so personal, it's hard to explain how it’s affecting us to family, friends and colleagues; something that’s particularly true when it comes to chronic pain."

How and why does arthritis cause pain?

Pain in arthritis is thought to be a result of damage to the cartilage or bone, as well as inflammation in the joints. Professor Philip Conaghan explains:

"In rheumatoid arthritis, pain arises from the inflamed joint lining tissue called synovitis. In osteoarthritis, pain may either come from damaged bone or from synovitis, and often from both.

Many people have weak muscles which lead to overuse of tendons, causing painful tendonitis, and pain where the tendons attach to joints, called enthesitis.

"It's common for people to experience more than one problem, for example osteoarthritis and tendonitis, sometimes in a single joint."

However, we still don't completely understand the causes of the pain of arthritis, as people with similar levels of joint damage seen on an x-ray can experience very different levels of pain. What we do know is the causes of pain in arthritis are complex, and can be influenced by changes in the ways in which the nervous system works, as well as by psychological factors.

Pain and the brain

Our spinal cord has special "gates" that can reduce or increase the strength of the pain messages from our nerves to our brains. They can block or deflect messages so the pain signal that reaches the brain is slightly altered.

Once the pain signal gets to the brain, it’s further changed by even more complex systems. Our pain messages can be affected by:

• how much we concentrate on the pain
• doing what we enjoy, which can take our mind off the pain and make it more manageable
• unhappy feelings, anxiety or depression which can make our pain feel worse
• prescription drugs that chemically reduce the impact of pain.

Treating pain

Pain occurs when special nerve endings send pain messages to your brain. Painkillers work by blocking these messages, either at the site of the injury (for example in arthritis this would be the joint), in the spinal cord or in the brain itself.

Different painkillers block different parts of the pain process, and since not all people experience pain in the same way, not all painkillers will work in the same way for everyone.

There are now more approaches than ever before to manage pain. As well as a range of drug treatments, there are complementary therapies and psychological therapies that can be successfully used to treat pain, as well as steps we can take ourselves to manage the pain we’re feeling.

Read more about pain and arthritis.

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