Is Chronic Knee Pain in Your Head?
When told that something is in your head, it usually means the person telling you that believes you are imagining. However, chronic knee pain is quite real and disabling for millions of adults in the US. It limits their mobility, disrupts their sleep and decreases their quality of life. You may be surprised to learn that for many people with chronic knee pain, particularly when caused by osteoarthritis, the severity of the pain may be associated with changes in the brain rather than the knee. In this post we will discuss this curious and important aspect of chronic knee pain. We also provide a brief questionnaire that you may find interesting. So please read on.
How is Pain Perceived?
Pain perception is a complex phenomenon, particularly if the pain is chronic. It involves many parts of the spinal cord and brain. Let’s say you touch a hot plate. Nerve endings in your fingers detect the dangerously high heat and send a pain signal to your spinal cord in the form of pulses called action potentials. These signals are relayed from the spinal cord to multiple areas within your brain, called the pain matrix, which leads to the perception of pain. There are many points along the way where the pain signal is modulated, meaning that its strength is increased or decreased. Different parts of the brain participate in pain modulation including those that are associated with mood and memory, which is why your perception of pain varies with your emotional state and, even, your memories. The perception of pain depends not only on the original source of the pain (i.e., the hot plate) but on how the resulting pain signal is modified as it makes it way to your brain where it is interpreted. In fact, sometimes there is no peripheral source of pain and the pain is entirely created within the brain. Phantom leg pain following amputation is an example.
Unfortunately, the pain processing systems in the spinal cord and brain can malfunction so as to increase your pain. This is called central sensitization. It is as if the pain volume control has been turned up, potentially way up. With central sensitization, minor pain that would have been ignored or only slightly bothersome may now be much “louder” and painful. And pain that was previously troubling and disconcerting but manageable, may now be disabling. Central sensitization may also lead to a phenomenon called secondary hyperalgesia, where an individual experiences pain in sites distant from the original source of pain. For example, someone with chronic knee pain due to osteoarthritis and central sensitization may feel pain in their shoulders and neck, even though they don’t have arthritis in those locations.
Why does central sensitization occur? Despite substantial research over the past several decades, there are still more questions than answers. However, a few things have been established. One is that persistent pain over a long period of time can lead to central sensitization. Another is that some people are more prone to developing central sensitization, potentially due to a genetic predisposition. Whatever the reasons, central sensitization is real and is associated with many chronic pain conditions, even those that were traditionally thought to be caused by localized pathology such as in chronic knee pain due to osteoarthritis.
Do I Have Central Sensitization?
Your physician may initially diagnose central sensitization based on your medical history, symptoms and a physical exam. There is a sophisticated diagnostic study called Quantitative Sensory Testing (QST) that can determine if you have central sensitization, but it is only performed in specialized neurology and pain medicine laboratories. You should discuss any concerns you have about central sensitization and knee pain with your physician.
The survey below provides a preliminary evaluation of your likelihood of having central sensitization. It is based on a clinical questionnaire called the Central Sensitization Inventory that was originally developed by Mayer and colleagues in 2012. A shortened version was subsequently created by Nishigami and colleagues in 2018. Fill out the survey to get your central sensitization score. Keep in mind that this survey is not a diagnostic test and is provided for informational purposes only. You should discuss the results and your particular chronic pain condition with your physician. Your responses to the survey will not be saved or shared with any entity.
If your score is 20 or greater you are likely to have central sensitization.
Can Central Sensitization be Treated?
The first line of treatment for knee pain is usually exercise, physical therapy and oral or topical anti-inflammatory drugs such as ibuprofen and diclofenac. If these measures are inadequate then direct injections of steroids or hyaluronic acid may be tried. Finally, more aggressive measures such as knee replacement surgery, called total knee arthroplasty, may be considered. But what if some part of the knee pain is actually due to changes in the brain? The aforementioned treatments are directed at the knee and you may be left with substantial untreated pain.
Can central sensitization be treated? The idea of treating the brain rather than the original site of pain, such as the knee, is new but some therapeutic approaches show promise in decreasing central sensitization. We will discuss treatment options for central sensitization in detail in a future blog post. In brief, certain pain medications, such as pregabalin and duloxetine have shown some benefit. Other approaches that may be useful include exercise, cognitive behavioral therapy and transcutaneous electrical nerve stimulation (TENS).
Can Quell Help?
Can Quell® help improve your chronic knee pain by reducing central sensitization? We do not have the specific clinical data to make that statement at the present time. However, leading experts in the TENS field such as Dr. Kathleen Sluka at the University of Iowa believe that regular use of TENS can reduce central sensitization and enhance the ability of the brain to inhibit pain. As the most technologically advanced, powerful and only true wearable TENS device available, Quell may be helpful in managing your chronic knee pain. You can try it risk-free for 60-days, so you have nothing to lose but your pain.
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