This is a summary of section 2 of “Explain Pain” by David Butler and Lorimer Moseley.

Tissue Injury 101

When a body is damaged, pain is often the best guide to promote optimal healing. Sometimes it is good for us to rest, other times it is better to move.

A similar healing process occurs for all tissue injuries. First, inflammation floods the injured area with immune and rebuilding cells. This reason is why inflammation is a good thing in early injury stages.

A scar forms once the inflammatory process is over. The tissue then remodels to attempt to become as good as the original. Blood supply and tissue requirements determine how fast the healing process occurs. For example, ligaments heal much slower than skin because the former has a lower blood supply than the latter. This may also be a reason why aerobic exercise may speed up the healing process.

If present, pain usually diminishes as the tissues heal. However, pain may persist if the nervous system still feels under threat.

Acid and Inflammation

The alarm sensors described here constantly work and often get us to move. Movement keeps our system flushed. When we don’t move or a physical obstruction is present (e.g. sitting), acid and by-products build up in the body tissues. Oftentimes we will start to feel aches and pains when we stay in a prolonged position, which is our body’s way of saying “get up and move.”

Much like the alarm system, inflammation is a primitive way for our body to continue the healing process. Inflammation is designed to hurt so the injured area has time to heal. There is no need to fret when swelling, redness, and pain are present; our internal systems are merely repairing us.

We call swelling and its corresponding cells the “inflammatory soup.” This soup is a by-product of blood and chemical transportation, and sets off our body’s alarm system to increase sensitivity. All of these changes are essential to facilitating a healing environment.

Muscles

Everybody be hatin’ on muscles nowadays as the source of our aches and pains. However, the authors put muscles in perspective for us with the following points.

• Muscles are loaded with sensors, so can impact the pain experience.
• Muscles can become unhealthy and weak.
• Muscles are very difficult to injure, they are just very responsive structures.
• Muscles are well vascularized which allows for quick healing.
• Muscle activity alters in response to threat and injury.
• Muscles reflect what our brain is thinking.

The Artist formerly known as disks – LAFTs

The reason the authors wish to change the name of these structures is because anatomically they do not resemble a disk at all. The new name is “living adaptable force transducers,” or LAFTs.

LAFTs are made up of the same material as your ear, and contain some very strong ligaments. In the medical world, we have many different treatment modalities that target the LAFT. We have McKenzie, traction, surgery, and injection to name a few. Because there are so many different treatments for these structures, it is fair to say that LAFT injuries are still not fully understood.

LAFTs also come with very strong language: slipped, bulging, herniated. Using such strong language can stop someone from moving, which is far from the ideal regarding low back pain.

Here are some LAFT facts.

1. The LAFT outer layer has a nerve supply, so danger sensors can become activated easily. If the LAFT becomes injured, the surrounding structures will likely set off danger sensors as well. You want a lot of danger sensors if something is occurring near the spinal cord. It is kind of a big deal.
2. LAFT injuries usually do not cause instant pain. Pain usually occurs 8-12 hours later.
3. LAFTs naturally degenerate and do not have to contribute to a pain experience. At least 30% (and potentially up to 80%) of people without low back pain have LAFTs bulging.
4. LAFTs never slip.
5. LAFTs heal slowly, but they will always be a bit tatty around the edges. This attribute makes it hard to distinguish aging from injury.
6. LAFTs, spinal joints, and nerves are built to withstand high forces.

Skin and Soft Tissues

Our knowledge of pain is based predominantly on the skin. The skin mirrors the nervous system’s state. Rarely is the case that skin injury leads to chronic pain however. On the flipside, painful skin zones; changes in skin health; and altered sweating or hair growth can all be indicators of damaged nerves.

How often have you seen or had your skin become increasingly sensitive to touch after an injury? This is a common phenomenon that occurs because cutaneous nerves increase sensitivity in order to protect an injured area. Here are some other skin and soft tissue facts.

• Damaged skin heals very quickly.
• Skin has a high danger sensor density.
• Skin is very mobile and loves movement.
• Fascia is a strong tissue that lies under the skin and also contains many danger sensors.
• Massage moves tissues and sends impulses to the brain. Therefore, movement and touch are great ways to refresh the virtual and actual body.

Bones and Joints

Most joints have lining known as synovium which keeps the joint contained and lubricated. This lining is loaded with danger sensors. Here are some other facts.

• Joint pain seems to be dependent at which the speed damage occurs. Slow changes usually do not make the brain think there is danger. A dislocation however may lead to severe pain. Most people with worn joints never know about it.
• Everyone has worn joints as we age. They are the wrinkles on the inside.
• Joints love movement and compression.
• Broken bones heal and are often stronger than before.
• Joints in the back and neck can get injured, but may be too small to see on imaging. This may or may not set off the alarm bells.

Peripheral Nerves

Most of today’s neuroscientists agree that peripheral nerve problems are far more common than we think. Here are some fun facts regarding nerves.

• Nerves have danger sensors.
• Neurons can contribute to pain.
• If a nerve becomes injured, it may become more sensitive to ensure you survive.
• Nerves slide as we move. If a nerve cannot slide well, pain may occur while moving.
• Nerves change as we age, just like everything else in our bodies.
• Scans and nerve conduction tests cannot easily identify a damaged nerve.
• Nerves can be injured but may not create a danger message for days to weeks.

The Dorsal Root Ganglion (DRG)

The DRG is like the brain of the peripheral nervous system. This is the first place that tissue messages are evaluated. Here are some facts for DRGs

• Peripheral nerves have their nucleus in the DRG. It is here that sensors are made.
• The DRG is extremely sensitive and changeable.
• The DRG is very sensitive to blood chemicals, especially stress chemicals.
• Sometimes the DRG fires just because. It is like your body’s car alarm. Sometimes the DRG can be hurt without having any pain too.

Backfiring Nerves

When a nerve is injured, oftentimes it will backfire. The reason for this is like a domino effect. If a nerve is stimulated at one end, it will send messages up the system to go to the other end.

Backfiring may not be an issue for the short term, but its persistence can lead to sustained inflammation. A less sensitive nervous system may lessen the amount of inflammation in the tissues.

Nerve Pain

Here are the common symptoms associated with peripheral nerve pain.

• Pins & needles.
• Burning.
• Night pain.

Here are potential locations

• Skin zones supplied by the damaged nerve.
• Small sensitive hot spots known as trigger points.

There are also some other potential qualities

• Movement often makes it worse, so you may adopt abnormal postures for relief (upper cross, elevated shoulders).
• Stress makes it worse.
• Unpredictable zings may occur.
• Movement or a sustained posture may ignite an injured nerve which keeps ringing.
• May not hurt for a few days or weeks.
• Skin zones may become itchy.
• Might just feel weird.

Just because you feel these symptoms does not mean it is the end of the world. Understand that nerves are just responding to signals from the brain that tell them to increase sensitivity and improve warning capacity.