Understanding Joint and Muscle Pain

By Noah Volz

Just like death and taxes it is rare that an individual will be able to go through life without experiencing pain. We have seen medical sciences spring up in every ancient culture and continue to grow until our modern medical model has been developed to treat pain. In both the ancient and modern systems hands on healing has always been an integral part of these treatment protocols.

As our modern understanding of pain grows from the early 19th century and the discovery of morphine’s effect on pain to the many types of anesthesia and analgesics that are used today in medicine we sometimes forget that massage has always been a part of pain management and treatment. In order to understand how massage can benefit pain it can be useful to uncover what we currently know about pain. It should be noted that most of our current understanding is theoretical and although evidence based the evidence is still incomplete.

The building blocks of pain

Most of the previous medical models of pain have relied on an understanding that compression of a nerve either by a muscle, bone, or disk herniation will cause pain. But more comprehensive research is finding that is not always the case. This model of pain has been coined the structural model. Implying that if the structure is sound then the pain will not occur. There is another type of pain caused by functional dysfunction outside of the body’s compensatory mechanisms.  Pain is most often defined as an unpleasant sensory and emotional experience that may or may not be caused by tissue damage. Pain is subjective and therefore there is no way to clinically determine if the pain being felt is in fact due to tissue damage. This is why the functional view of pain is useful.

Pervasive in our bodies are sensory nerves that relay the feeling of pain to the brain. Beyond this mechanical transmission of pain is how we interpret the pain. It can be helpful to determine the pain’s location, intensity, quality, emotional response and onset. This will start to paint a more complete picture of the pain pattern. Pain is really only a warning signal that something is not working correctly and must be changed or repaired. I am sure that everyone you know has at one point complained of pain in the back, neck foot or head. No one is immune to pain.

Movement
In Ayurvedic medicine prana is defined as movement and in terms of the skeleton this movement originates and is created because of the joints. Joints are designed to provide movement. Just like all of life the life of a joint begins with movement. Not just movement but a variety of movement is the best way to keep the joints healthy. If the types of movement we choose are always the same we run the risk of overusing the soft tissues that comprise the joint.

Wear and tear in the joints is created when the fluid nature of the joints begins to dry up. This is why many more joint pains are common in old age. Through friction and compression joints deteriote and this loss of fluid within the joints allows the more dense tissue to come into contact with one anther. When the joint is in proper alignment and the soft tissue’s have balanced engagement it can delay deteroation from old age.

Pain is on the Run

Pain is not a one size fits all phenomenon. Even when the cause of pain is identical within two people it does not feel the same. The primary causes of pain are injury, illness, depression or in the absence of an identifiable cause. Pain can severely compromise our lives as it takes a significant amount of brain activity to deal with the pain we feel. This is because the nervous system is always working towards order. The body does not want to be in pain and soothe the body’s natural healing intelligence is already working. The job of a bodyworker is to tune into those corrective mechanisms and help them flourish. When this happens the symptoms of conditions such as frozen shoulder, sciatica or plantar fasciitis will continue to make steady improvements until there is a complete reversal. It is important to keep a positive attitude and remind oneself that they are improving instead of not feeling like they are healed yet.

The pain pathway

Pain is transmitted through three primary pathways in the central nervous system: peripheral nerves, spinal cord and brain. The peripheral nerves are a widespread web of sensory pathways within the body. The primary sensors for pain are called nociceptors and they sense unpleasant stimulus in every tissue in the body. The more nociceptors in one area the more pronounced the pain signal. In general the skin has the most, the muscle second, the bones third and the internal organs fourth. These receptors are here to protect the body from danger. When there is a harmful stimulus the peripheral nerves then exchange information with eh spinal cord where the impulses are related immediately to the brain in order to initiate a response. Depending on how vital the tissue is to survival the message may move fast or slow. A headache which affects neural tissue will have a faster response time than a chronic knee injury.

Within the spinal cord are gates that are guarded by specialized nerve cells. The gatekeepers filter messages in order to determine the severity of the pain. The more severe the more quickly it is transmitted to the brain. The spinal nerve cells also can initiate quick motor responses like reflexes in order to remove the body part from the pain inducing stimulus. This is often referred to as the gate theory of pain and has been extensively researched by R. Melzack and P. D. Wall. Pain signal transmission from the peripheral nerves to the spinal cord can be altered by manual therapy in the form of pressure. The primary understanding is that pain signals sent by the spinal cord are downgraded through the simulation of the receptors, no longer indicating that the pain is an emergency. Although receptors on the skin are important there are other receptors that can provide a more pronounced therapeutic effect. Specific receptors in the joint capsule called articular receptors and are stimulated when there is range of motion within the joint. This often adds to improved therapeutic outcomes.

The last stop on the pain train is the brain. The first place that the messages arrive within the brain is the thalamus which is a kind of switchboard that forwards urgent messages to important regions of the brain such as the frontal cortex, somatosensory cortex or the limbic system. Each one of these areas determines how we will think, sense and feel based on the stimulus. This allows the response to the pain to be adequate to the affect on our ability ti think sense and feel. Pain cannot be separated from our past experiences which can either promote an excessive response or insulate us against pain.



How to Use Pain

Although many of us consider pain a nuisance at most and a tragedy at its worst we sometimes forget that pain’s primary goal is to allow us to avoid danger, prevent further damage and promote the healing process. Pain is the first step in the healing process and often the indication that the process is complete. Unfortunately assessment of musculoskeletal pain is not as straight forward as broken bones or infections that can be measured by X-rays and lab tests. In order to get better results it can be helpful to understand the dominant theories of pain.

Descartes Specificity Theory of Pain

Although developed in 1664 this theory of pain says that the magnitude of tissue injury will have an equal and proportional pain response. If you prick your finger the pain response is determined by the amount of tissue damage and is minimal. If you break a bone the amount of tissue damage is extreme and thus the powerful response. Another aspect of the specificity theory is that if you take away the pain you have removed the tissue damage. Taking pain killers does not fix the injury it just stops the experience of pain. This theory may be relevant for acute pain, but it does not shed light on chronic pain conditions. One example of how this theory does not work is phantom limb pain. Another example of how this theory falls short is using hypnosis or acupuncture as anesthesia while receiving surgery. The tissue damage sustained during surgery does not create a pain response because of the hypnosis.

Gate Theory of Pain

Developed by Ronald Melzack and Patrick  the gate theory conceptualizes a pain conduction model that is the dominant map used in both the medical and manual therapy communities, even though the biological mechanisms are not fully understood. Gate control theory1 suggested that the messages carrying information about injury go along two separate nerve fibers. One fiber is called a mechanoreceptor and they transmit messages about movement, heat, pressure, etc. The Nociceptors mentioned earlier carry pain signals. The information from the mechanoreceptors reaches the brain first and when the sensations received by those receptors are normal then the pain signals that follow will not register. The stimulation of pain in the brain thus requires a disruption in the sensory information sent by the mechanoreceptors.

This returns us to the functional model of pain mentioned earlier. That the function of the joint and the ability for stress free or low stress movement indicates an absence of pain. Thus if the mechanoreceptors stimuli are normal the gate that the pain message goes through is closed. If however the mechanoreceptors are registering functional problems then the gate will be open to pain signals regardless of the amount of tissue damage. Other methods to close the gate are do secrete endorphins which are the bodys natural pain killers. These are secreted with eustress, excitement, exercise and happiness.

How Manually Therapy Helps Pain

If the gate theory is accepted then it is easy to see how massage can provide benefit for pain. Pressure, heat and movement at the area of pain changes the signals sent by the mechanoreceptors. This change’s the experience of pain on a physiological way. Thus the true ability to cure pain happens in our brain and is based on the stimulation that the brain receives. This is not to say that there is not some amount of tissue damage. For example prolonged head forward posture from staring at a computer screen can compromise the facet joints causing alterations in normal mechanoreceptive cerebral input. As the tissue sending these signals break down the nociceptors are able to take the place of those signals. If mechanical deformities and inflammation develop then the brain is bombarded with pain signals which will result in protective muscle guarding, postural distortions and anxiety. This new pattern becomes the norm and the body will be able to adapt to reduce pain even though the damage is still there. Pain free movement is not an end in itself is postural integrity is not also established.

When all tissues on both sides of the joint has mechanoreceptors sending signals that are not compromised then we experience a reduction in pain and an improvement in flexibility. This can be accomplished by relaxation massage which affects mechanoreceptors on the skin and fascia. Joint pain may need a stimulation of articular receptors as well in order to reset mechanoreceptor engagement. These articular receptors are commonly loaded meaning that there are a higher proportion of pain receptors within the joint than mechanoreceptors we may be built to experience joint pain before it gets worse.

This creates a challenge for intervention. The overall goal of manual therapy is to reduce the excitability of the pain pathways and interrupt the pain generating stimulus in order to remove the memory implanted on the nerve cells. This will improve mechanoreceptive activation and reduce nociceptors signals that make it through he gate.

Conclusion

As we each will experience some level of physical pain over our lifetime it is helpful to know that pain is not always caused by structural dysfunction and can be the result of more subtle signals from the joint capsule. Most pain conditions develop slowly over time and are not the result of a specific trauma. Although we would like to believe that all pain can be seen through he naked eye and has a clear diagnosis this is relatively uncommon. This is where the gate theory sheds light on how sustained compression, improper loading, tension and poor posture will change mechanoreceptive and nociceptive signaling to the brain resulting in signals of pain. Manually therapy can change this signaling and thus change the experience of pain.

Notes

1. T. Melzack and P. D.Wall,“Pain Mechanisms:A New Theory,” Science 150 (1965): 971.
2. R. Melzack and P. D.Wall,“The Challenge of Pain,” (United Kingdom: Penguin, 2004), 35.
3. S. C. Mackey and F. Maeda,“Functional imaging and the neural systems of chronic pain,”
   North American Journal of Clinical Neurosurgery 15, no. 3 (2005): 269–88.
4. V. Janda,“Treatment of chronic back pain,” J Man Med 6 (1992): 166–168.
5. J. Mennell, Joint Pain, (Boston: Little Brown & Company, 1964), 224–259.
6. A. M. Burt, Textbook of Neuroanatomy, (Philadelphia:WB Saunders, 1996), 311.
7. R. F. McLain,“Mechanoreceptor endings in human cervical facet joints,” Spine 19 (1998):495–501.
8.  S. R. Garfin et al., "Spinal nerve root compression," Spine 20 (1995): 1810-1820.
9. Eric Dalton, Advanced Myoskeletal Techniques (Oklahoma City, OK: Freedom From Pain Press, 2005), 284.
10.  R. Melzack and P. D. Wall, "Pain Mechanisms: A New Theory," Science 150 (1965): 971.