How Pain Works

Edited by: Eoin Lombard

Pain is a complicated subject and difficult to condense down. This article will attempt to give you a grasp of a few basic concepts and don’t worry, there’s no need to fully understand it on the first read through!

Pain is one of the biggest motivators we see when it comes to seeking out help from a physiotherapist who plays an important role in the management of both acute and chronic pain. At PhysioHub, we see a wide range of pains from neck to elbow to knees to hips, all varying in their presentation. Not all pain is created equal, therefore it is important to have a thorough assessment done by your physiotherapist in order to identify the root cause of your pain. Your therapist will then work together with you in order to design a treatment program that suits your specific needs.

Our evidence based practice and experience has shown us that a combination of exercise and manual treatment results in the best resolution of pain, something that is backed up by the current research base. Your physio may prescribe exercises that promote strength, mobility and flexibility in the muscles which can stimulate the body’s own natural painkilling mechanisms whilst also promoting movement and functionality in painful joints. You may just want to not move, take painkillers and wait out the pain, but in most cases this is not the best way to manage your pain! Understanding the way pain works can help you to overcome it so check out our page on “Pain Psychology” to learn more.

Manual therapy can also be a useful adjunct when it comes to pain management. This can provide short term pain relief in order to practice your exercises with a little bit more freedom in order to make that relief stick. Types of manual therapy your physio might use include massage, mobilisations, dry needling, heat, ice etc.

It is important to us at PhysioHub to maintain a multidisciplinary approach to your pain management so we will communicate with your medical team if necessary to ensure that you have the soundest resolution possible.

Part 1: Acute Pain
Pain is a normal bodily function which is designed to work as an alarm system to draw your attention away from whatever you're doing and focus on getting your body out of harm’s way. This type of pain is USUALLY temporary and linked to the tissues of the body. When a tissue is damaged for example, a signal is transmitted to the brain and spinal cord through specialised nerves called nociceptors. This signal is carried to specialist parts of the brain to be processed, usually as pain. Note that pain is a product of the brain and not the tissues, the signal is not perceived as pain until our brain tells us that it is painful. These specialised nerve fibres can be further divided into what are called Aδ fibres and C fibres. The Aδ fibres are large, thick nerves which transmit signals to the brain and spinal cord at a rapid pace, these are responsible for that initial jolt/jerk that you get when you touch a hot stove for example. The C fibres on the other hand are smaller and slower so are always catching up the Aδ signal, these fibres are responsible for the dull, achy feeling you get afterwards.

So how does knowing this help you with pain? Well we can use what we know about these fibres to put into effect what is called the Pain Gate Theory. Have you ever bumped your elbow and started rubbing it to help the pain? Or hit your hand and started to shake it about? This is classic Pain Gate Theory in action! Pain receptors and other nerves responsible for things like touch, vibration, pressure etc. (mechanoreceptors) all need to enter the spinal cord through a similar pathway. This means that only a certain amount of signals can be carried up to the brain and processed at the one time. Think of it like a “gate” at the spinal cord only letting through a certain amount of signals at a time (a bouncer at a nightclub is also a nice analogy!)

Mechanoreceptors again are types of A fibres, really quick at transmitting signals. Because the dull achy pain we feel afterwards is carried by the very slow C fibres, the spinal cord is preferentially going to block, or close the gate to, the pain signal in favour of the much faster touch, pressure or vibration signal, hence you feel less pain. This concept is similar when we use things like heat packs, ice packs, TENS machines, massage, dry needling etc. The signal generated by the ice pack, or whatever it is, is going to be preferentially taken to the brain over the pain signal. There is almost always some sort of pain gate theory going on when we introduce a new stimulus to take away pain.

It is also important to note that none of these modalities will cure the underlying cause of your pain, they only serve to act as pain relief and a period of rest and rehabilitation is normally required during the period of pain relief to get nice and strong once again.

If you are in this type of pain, come chat to our physiotherapists about what pain relieving modalities may work for you and how you can speed up your recovery from injury.

Part 2: Chronic Pain and the Pain Cycle
So far we have talked about acute episodes of pain that are temporary and consistent with normal tissue healing times. But not all pain is created equal. What happens when it sticks around? What happens if there is no identifiable tissue damage? Pain that endures for long periods of time (3-6 months) is classified as chronic pain. Factors such as your genetics, physiological mechanisms and even psychological mechanisms can make pain persist. The longer pain persists the better the nerves become at conducting pain, less of a stimulus is required to trigger them and they can lose their capacity to be specific and precise so the pain begins to spread. Chronic pain can lead us into a vicious cycle as illustrated below:

How we get out of this cycle is the question. For many people, this begins with increasing their activity with exercise. It sounds counterintuitive, but think about what we have talked about before. This is pain that is persisting long past normal tissue healing times, so more than likely you are not going to do yourself any damage by getting active again! This advice is consistent whether you have a vague unexplainable back pain but also in many chronic conditions such as arthritis and osteoporosis. Medical and pharmacological interventions are still important and our physiotherapists will work in conjunction with your team to ensure you have the best outcome. The same modalities as mentioned earlier (dry needling etc.) can act to desensitise what is essentially an over-sensitised nervous system and turn down the volume knob on your pain experience. As well as exercising, avoiding catastrophisation and taking care of your mental health, quality sleep and a good diet, can all help you break out of this pain cycle.

At Physio Hub we have lots of experience in dealing with rehabilitation following orthopaedic surgery, particularly total knee replacements. If you are suffering from knee pain and would like some advice on the best management plan, or if you have just had surgery on your knee, give us a call to make an appointment where we can complete a comprehensive assessment and support you in making the best decision to manage your pain and return to optimal function.