We’ve all experienced physical pain in our lives – a cut finger, a stubbed toe, an ankle sprain, headache, sore throat, or even perhaps after an operation. We can understand that it varies from mild to severe, and can last briefly or a few days. Pain serves a purpose – if you break a bone in your leg, you avoid standing on it and rest up until the fracture heals. We also have a psychological response to pain, and it can really help to reassure us (and therefore reduce its impact or intensity) if we can understand the cause of the pain. Let’s consider the broad causes of pain and then hopefully we can tailor solutions to get ourselves better.
Muscular pain is the most common cause of pain, and is one of the most frequent reasons people consult their doctor. This can result from an acute injury, such as an ankle sprain during sports, or longstanding back pain from a poor posture, poor technique in lifting heavy objects, or a sedentary lifestyle. Muscular pain usually occurs on movement, especially when you activate that specific muscle group. Healing is helped immediately after an injury to rest, ice packs, and simple painkillers, if necessary. In the medium term, you need to get moving and stretching the injured muscle group – not to the point of pain, but it might feel a bit uncomfortable, and painkillers may help to get this rehabilitation done. In the long term, you need to consider what caused the injury – did you warm up properly before a match or gym session, were you using the right technique to lift something, could you improve your core and adapt your workstation to improve posture? Bone pain is similar, worse on movement, but may be constantly present on some level, and will gnaw away at you. You wouldn’t ignore a broken leg, but sometimes people have more subtle disease processes affecting a bone. It can feel severe, and may wake you at night. It’s important to get any persistent pain that wakes you checked out by a doctor.
Nociceptive pain occurs when there is damage to a particular part of the body and it alerts your brain to the problem via nerves. It includes muscular and bone pain, but also pain from a blister where your shoe rubs, an oven burn on your finger, joint pain from inflammatory arthritis, tooth pain, chest pain from angina, abdominal pain from appendicitis. In essence, damage to a particular tissue alerts the nervous system that something is wrong, and it tells the brain to do something about it (like take your hand off the hot plate). It will be made worse or better in certain positions, with certain movements, or worse with load (lifting or weight bearing). Some divide this further into visceral and somatic pain. Visceral pain is more likely to involve organs and their connecting structures, and it’s therefore often diffuse and hard to pinpoint. Examples include a blocked urinary catheter, kidney stones causing obstruction, angina, appendicitis or a stomach tumour. People describe it as crampy, deep, throbbing, sharp, intense, and sometimes feeling like a pressure or heaviness, especially when it relates to the heart. Somatic pain originates from skin, joints, muscle or bone, and any of their connecting tissues, and it’s probably more familiar to us. People use words like sore, burning, sharp, aching, deep, dull and gnawing. It will usually be quite focused so people can point to the problem area with accuracy.
This is when a nerve gets pinched (a trapped nerve, commonly in the neck), inflamed, such as in sciatica, or damaged, as in diabetes, alcoholism or multiple sclerosis. It’s damage to the nervous system itself, rather than a part of the body alerting the nervous system that there’s a problem. Neuropathic pain can involve the peripheral nervous system, such as nerves to the arms or legs, or the central nervous system, which is the brain and spinal cord. You may get neurological dysfunction, such as reduced muscle power, pins and needles, tingling or numbness or reduced sensation to touch. Carpal tunnel syndrome is a good example, where a particular nerve, the median nerve, gets squeezed as it goes through a narrow tunnel or bones and tendons in your wrist, causing distinctive tingling and pain in certain fingers. People often describe shooting or stabbing pains that stop them in their tracks, or a burning sensation. Think of when you hit your elbow, the “funny bone” – you are actually pranging the ulnar nerve that passes down the arm to the hand, rather than the bone. It’s one that can be debilitating in its intensity and one that’s tricky to treat. Any trapped nerve needs to be released and it will gradually recover, such as in sciatica, where the sciatic nerve is squeezed as it goes through gaps in the pelvic bone by certain muscles – if you work on releasing your hamstring muscles, it will gradually improve, but this is difficult in the initial phase. Neuropathic pain is more likely to lead to chronic (longstanding) pain.
Pain is sometimes a combination of nociceptive and neuropathic pain. Shingles is a good example – after catching chicken pox as a child, the virus remains dormant in nerves connected to a part of your skin called a dermatome – once reactivated, perhaps when you’re a bit run down, it causes gnawing nerve pain deep in the skin. It also causes a blistering rash on the skin’s surface, which can be painful, too. Pain may be referred, where one area is injured or damaged but the set-up of your nervous system means you feel it elsewhere. Your appendix is low down and on the right hand side of your abdomen, but inflammation can initially start around the belly button, far away from the appendix. Pain may not easily fit under nocicpetive or neuropathic categories if there is disruption to the nervous system. This is likely to be the case in fibromyalgia, irritable bowel syndrome (IBS) and headache of unknown cause. Persistent or episodic pain lasting more than three months is termed chronic pain. It’s a complex area of medicine, and very difficult to treat, as your nervous system adjusts to this, with sensations becoming heightened and more widespread. The complexity comes from our higher processing, where pain can start to prevent everyday activities and dominate normal life. The consequent reduced distractions and the fear of pain means it is further heightened. Chronic pain is more likely to come about from the “slow pain fibres”, which are loudly telling you that there’s injury, you should rest and recover by not moving much. This is as opposed to the fast pain fibres that let you know your toe has been stubbed and you move away from the external threat (with much hopping and howling). But resting for months on end is unlikely to serve a useful purpose, and often sets up new problems, both mentally and physically.