Pain Pie
PAIN IS VERY HARD TO DESCRIBE FOR EVERYONE. IT IS COMMONLY SUMMARISED AS “IT JUST HURTS, DOC”.
But if you think about it, pain is made up of many different sensations and emotions. It may just be an ache for some people, but for others it can burn, stab, be intermittently sharp, be associated with muscle tightness, pins and needles, or a myriad of other symptoms. There may also be an underlying cause that contributes to the pain and consequences of it, which generally impact on how you sleep, and how you feel, and how you do the things you love.
The Pain Pie is simply a way to think about pain. There is no magic research to it, it is just a means of trying to explain that pain is not just one sensation. From a technical perspective, the Pain Pie is made up of the 3 components of the pain system, and each component broken into pieces of the pie. The blue sections are pain arising from body parts, the white sections highlight pain arising from nerves, and the dark gray sections include pain coming from or amplified by the spinal cord and brain. Each piece of the pie has its own characteristics and treatment options. Some of these are distinct, others overlapping.
The Pain Pie is also an attempt at not getting caught in thinking there is just one solution to pain eg. “I have an operation that will fix you” or “All you need to do is think differently about your pain”. These approaches may form important parts of helping treat your pain but they may not result in significant decreases in pain when used alone. What’s more, if these don’t work, it doesn’t mean there are not more options. The Pain Pie can be used to identify all the pieces of your pain, rather than treating just one piece. For example, we can treat a patient with inflammatory pain by prescribing anti-inflammatories and only decrease their pain by 10-20%. Or, we can treat several pieces of the pain pie at once with the aim to shrink the entire pie and get a greater overall improvement in pain.
somatic/VISCERAL OR NOCICEPTIVE PAIN
“Soma” is another word for “body”. You can think of “somatic pain” as pain arising from a “body part”. The big question is always “Which part?” Somatic pain can be described as aching, broad, heavy, sore, sharp, pressure or throbbing. It refers or radiates to different areas, sometimes specific for a body part, but commonly not. If the pain is in a small area, like a golf ball, it may be easy to work out what is causing it. If it is over a wide area, football size or bigger, it is harder to find (Don’t worry, there are ways to make the area smaller).
To complicate things, your body will refer pain from different body parts to the same place. Below is a picture of the referral patterns of sources of lower back pain - sacroiliac joint (yellow), facet joint (blue), hip (purple), disc (green) and nerve root pain (orange). As you can see they all overlap, making it difficult to identify pain simply based on where you feel it.
Suffering purely somatic pain is surprisingly not that common. If you do have just somatic pain, managing it becomes focused on identifying the possible cause (if you can) and settling any sensitisation (Sensitisation can be thought of as the pain being amplified). Read the sections on “Cause” and “Sensitisation” to get an idea in which direction to head.
The word “viscera” refers to all your internal organs, eg heart, lungs, kidneys, liver etc. So “Visceral pain” is just pain coming from one of your organs. Visceral pain is generally felt as a deep ache. Depending what organ is involved, and what is causing the pain, the pain will be in different locations (eg heart is generally in your chest, neck, back and arm), and features. Although visceral pain is an important part of pain. The majority of chronic pain is somatic pain, coming from arms, legs, backs and necks. As this is the biggest problem, this is our main focus.
In this situation, you would think a scan may be of use. Unfortunately, this is commonly not the case. For lower backs, 83% of people with NO PAIN will have a disc degeneration, a bulge, protrusion or extrusion. The picture below gives you an idea of what is “normal” on a back MRI.
For back pain, because what the pain feels like, where it is, and scans are not very accurate at diagnosing pain, the way to diagnose lower back pain is to block or “numb up” specific structures or their nerve supply, and see if your pain goes away. This is done in a methodical fashion starting with the most likely structure based on your story, examination and imaging findings. Numbing up the area is commonly done twice with different local anaesthetics to confirm the pain actually goes away. If done is this way, 85% of the origin of pain can be identified.
cause
The cause of pain can be obvious at times and elusive at others. In many cases the original cause may have healed and you are just left with the pain. In other circumstances, the pain may not be coming from where you would expect. For example, in knee osteoarthritis, 32% of the pain comes from structures outside the joint, and treating the problems inside the joint may not result in decreasing the pain.
In lower backs, there is 5 main causes of pain; facet joints, sacroiliac joints, hips, discs, and nerves. To help identify which one is the primary cause of pain, doctors ask a range of different questions like what triggered it, where it’s located, where is radiates, what makes it better or worse and any associated symptoms to try pin down which one is the culprit. Unfortunately, many of the answers are not specific for one structure and if you are in a lot of pain, everything hurts.
Contributing factors
Contributing factors include hypermobility, deconditioning, strength, weight and joint alignment. Core stability also falls into this group. Identifying these and addressing them is an important part of getting on top of your pain.
Myofascial pain
Myofascial features are muscle tightness and trigger points. Trigger points are commonly under estimated as sources of pain. They can create focal pain and pain that will radiate over a wide area that imitates, neuropathic and somatic pain.
Myofascial pain commonly responds to massage, acupuncture or manipulation, the relief of which, lasts from 1-3 days. In many cases the muscle pain can be secondary to the underlying cause. For instance, facet joint pain in necks and lower backs commonly causes a significant degree of muscle tightness.
You may also develop muscle tightness due to muscle weakness. Thought of simply, the muscle has to continue to do its job (eg it has to continue holding you up). If it is too weak to do so, it gets tight as a means of compensating. In this situation a strength program becomes essential for improving pain.
bony pain
Bony pain is a little more difficult to define. This is pain on impact (eg you stand up and get pain, you sit down, it goes away), pain on pushing over the bone, and pain that wakes you at night. It can be very difficult to identify this type of pain in lower backs or necks, and is more easily recognised in knees, legs and feet.
Bone pain can be address with decreasing the load on the bone and allowing it to settle, as you would with treating a fracture. In Addition, bisphosphonates, a type of osteoporosis medication have also been shown to be quite useful to settle the bone pain related to osteoarthritis.
inflammatory pain
Inflammatory pain is worse in the morning and after rest. It is associated with stiffness and swelling, improves with heat, is worse with cold and commonly transiently responds to anti-inflammatories. Inflammatory pain can also wake you or make it difficult getting to sleep, and will change with the weather (eg your knee may be able tell you when it is about to rain).
Most people have an inflammatory piece to their pain. For osteoarthritis, the morning stiffness lasts between 5 and 60 minutes and settles as you warm up. If you have stiffness that lasts more than 30-60 minutes, or “stiffness” rather than pain is the primary problem, these may be an indication of an inflammatory disease such as rheumatoid arthritis, or one of the other inflammatory joint problems. This should be a trigger to discuss this with your doctor and consider seeing a rheumatologist, as there are many new and effective options for treating these conditions.
If you are in the same boat as most people, your morning pain and stiffness lasts a short period. There are a range of medications, injections and natural options that may be effective to help settle this component of your pain.
Medications used to settle inflammatory pain include anti-inflammatories. (NSAIDS) such as meloxicam, naproxen, diclofenac, and ibuprofen to name a few. Prednisone is oral cortisone, it is an anti-inflammatory that works differently to NSAIDS. Both NSAIDS and prednisone can have some significant side effects and use of topical versions, particularly for in knee and hand osteoarthritis can be safer and as effective.
Injectable options include cortisone, hyaluronic acid and platelet rich plasma. These work with variable effectiveness depending on the condition being treated. I expect we will see stem cells added to this list in the future. That said, stem cells is a new developing technology. There is currently scientific evidence for using them in osteoarthritis of the knee and building evidence for intervertebral disc disease.
Mechanical pain
Mechanical pain has a number of different descriptions. It is generally pain that comes on when people move, or bend/twist in a specific fashion and goes when they stop that action. I don’t find this definition overly helpful and think more in terms of “Mechanical features” of pain which include painful clicking and clunking, giving away, locking and decreased range of movement. It depends on the body part involved as to what will be the cause. In the case of mechanical symptoms they may, but not always require an operation to address.
For example, in the case of ACL tears, although in Australia we repair nearly all of them. Studies from Scandinavia have shown that only 50% of people likely need an ACL repair, and that with good rehabilitation those that don’t have a repair return to the same level of exercise as those that do.
vascular pain
Vascular pain is also known as ischaemic pain. When it comes to pain from arms, legs and backs, this type of pain is less common, but is seen in people with peripheral vascular disease. It is due to poor blood supply to a muscle. As the muscle starts working the blood supply can’t keep up, this results in pain. It is most commonly seen in calf or thigh pain and going up-hill or stairs is a frequent trigger. Once you stop the activity, the pain goes away quickly. Diagnosing the pain and identifying the point of blockage in the blood vessels are the first steps.
Treatment is then dependent on the cause. This may include, addressing things like high blood pressure and cholesterol, ceasing smoking and getting diabetes under control. Combining this with an exercise program has been shown to be effective in helping improve this type of pain. Beyond this, balloons or stents are used to widen a narrowing, and Botox can be effective where bands of muscle are responsible for compression of the vessel. Finally, if all fails, treatment involves surgically bypassing the blockage.
Neuropathic pain
Neuropathic pain is pain due to nerve damage or disease. However, people commonly present with “features of neuropathic pain” with no nerve injury. This is seen commonly in shoulder pain which can have intermittent pins and needles to the hand. This is probably nerve dysfunction or irritation in those nerves supplying the hand. “Neuropathic pain” includes sensations such as burning, pins and needles, numbness, electric shocks, itching, crawling (formication) and pain on light touch (allodynia), painful cold and squeezing. The sensation also come on randomly with rhyme or reason. Neuropathic pain is also commonly associated with the pain being much worse than expected (hyperalgesia), and it can create a large degree of emotional distress.
This type of pain is treated with medications and neurostimulation. The most common medications used are amitriptyline (Endep), pregabalin (Lyrica) and duloxetine (Cymbalta, Andepra). There are a range of other medication, but these are all less effective than these four. Amitriptyline and duloxetine are anti-depressants and pregabalin an anti-epileptic. They can be thought of as nerve stabilisers and they reinstate the normal mechanisms that inhibit pain. They have list of side effects as long as your arm, but the primary issues with all of these is drowsiness. This can be dealt with by starting with a low dose and gradually building up. They are metabolised differently, so if side effects are a problem, swapping between them may be useful. They can also be used a creams. This decreases the amount of absorption into your system and can decrease side effects. If you don’t tolerate any of them, we can consider other medications, or just stop them and move onto the next option. If you are on one of these medications already it should be trialled for 4-6 weeks. If during that time you don’t tolerate the side effects or it is not effective, it should be stopped.
Neurostimulation is the use of electrical pulses to alter nerve function and decrease pain. It involves the insertion of leads either under the skin, or within the spinal column. The lead is then connected to a battery which sits under the skin and delivers the impulses.
There are a number of options for neurostimulation. Percutaneous electrical nerve stimulation (PENS) is where stimulation is delivered for 60 minutes and no leads are left in place. It can effectively decrease pain for 6 -12 months. Peripheral nerve stimulation is similar to PENS but it is a permanent implant where leads are placed under the skin to stimulate peripheral nerves. This can be effective in the treatment of headache, chest wall pain and focal buttock pain. Leads can also be placed in the spinal canal to directly stimulate pain fibres in the spinal cord. This is referred to as spinal cord stimulation and is used for people suffering lower back and leg pain. The last version is dorsal root ganglion stimulation. This type of stimulation targets the nerves as they enter the spinal canal and is particularly good for focal nerve pain.
sensitation
Sensitisation can be thought of as amplification of the pain. Key indicators are: Severe pain out of proportion to the injury (eg little injury but big pain). Pain that is unpredictable, always there, spreads or moves, has multiple things that trigger it off, is associated anxiety or depression and social issues, such as job loss, financial stress or relationship issues.
Sensitisation can be pictured as the ‘volume control’ for your pain. Commonly, pain is ‘turned down’ (eg it is silent), particularly from degenerative problems, which normally don’t cause pain. But changes occur in the nervous system resulting in the volume being ‘turned up’, and “Things that shouldn’t hurt, do hurt, and things that should only hurt a little bit, hurt a lot”.
There are many things that will drive sensation. The pain itself, fear, loss, doctors and other clinicians repeatedly telling you something is wrong, financial stress, conflict, and relationship problems. There is probably a range of metabolic issues that drive it like, diabetes, metabolic syndrome, and gut microbiome issues to name a few. A common sensitiser is scan reports with words like “severe” and “degeneration” mixed in with a little Latin or Greek like “spondylolythesis”, to make it sound terrible. Most of the time, these changes are normal part of getting a little older. In a population of 20-year old’s with NO BACK PAIN, 37% will have disc degeneration and 29% disc bulges on scan. Many changes on scans are just like “wrinkles”, and unfortunately, we all get wrinkles.
EMOTIONAL AND COGNITIVE CONSEQUENCES
If you are in the minority, you tolerate pain fantastically and soldier on with no effect on your life or how you feel.
If you are like nearly everyone else, pain makes you feel down and generates a degree of anxiousness or fear about the things that make your pain worse. When these feelings begin to impact on your ability deal with everyday life we label them as depression and anxiety. The annoying thing about this, is that the depression and anxiety can then make your pain worse. It is a vicious, unfair cycle.
Recognising depression and anxiety as being response to pain and not “your fault” or a “sign of weakness” is unbelievably important. You can then get on treating them with the aid of a psychologist, meditation, exercise or some medications. Treating the depression and anxiety is just another tool to improve your pain.
SOCIAL CONSEQUENCES
The social consequences of pain should really be at the start of all this not the end. When asked to rate how bad pain is out of 10, most people actually rate how much it annoys them, not how much it actually hurts. I have only ever had one person say to me “Dan, my pain is 1/10, but it annoys me 9/10”. This is probably the most important thing about pain for most people. It is not how much it hurts, it is what pain takes away that is most important.
Pain is a thief. It steals the ability to work, your role in the family, intimacy and the things your love doing. Acknowledging this and setting some personal, important goals is essential to help motivate you through getting on top of your pain. From my perspective as a doctor decreasing your pain is a “result “not a goal. A goal is getting back to walking the dog, kicking the footy with the kids, working in the garden, getting back to work, traveling or whatever is important to you.
Having the things you love and your role in the world taken away makes your pain worse. Getting them back will help improve it too. So don’t wait to be pain free to achieve your goals, because achieving them will also help decrease your pain.