Post by Sam Donaldson (M.PhtySt, BAppSci(HMS), Physiotherapist APAM SMAM)
Pain and pain science is an ever evolving and incredibly complex field of study with many, MANY contributing factors. For some more information on what pain is, how the brain is involved and why that is important to be aware of, see a previous blog posting by Tim: http://www.rhpphysiotherapy.com.au/uncategorized/is-it-all-in-my-head/
In some musculoskeletal pathologies, pain may feel worse at night time. This can be a harrowing experience and quite disconcerting. Typically, we think of night pain as suggestive of more sinister pathologies. So, importantly, mention this to your physio at the next appointment or discuss it with your Doctor. Even more importantly, often there is a very normal cause for this pain.
One such instance is bone related pain. A stress reaction or stress fracture is a good example. Bone stress injuries occur because of an unfamiliar increase in physical activity and is related to overuse, under recovery and several considerations that result in the bone not being able to keep up with the required adaptations.
A fracture can result and this will cause pain at night time. It has been proposed that this may be a result of attention. We are busy throughout the day, the mind is attending to many inputs and outputs, which we don’t attend to at night. Perhaps the brain allows this pain stimulus information to come to the fore?
Another explanation, scientifically justified, is related to our circadian rhythm and inflammation. Healing tissue requires inflammation to occur, bringing cells to the area that work to fix the problem. Interestingly, our circadian rhythm aids in modulating this inflammatory response, particularly for bones. Markers for bone turnover fluctuate throughout the day in a diurnal pattern, with increased metabolic action occurring at night. This might be due to an interaction of hormones controlled by the brain and responsive to day/night environments. They allow the increase in inflammatory markers and thus an increase in bony metabolism at (Dimitri & Rosen, 2016).
As Tim wrote in his blog, inflammation increases the responsiveness of nerves. Bones are innervated. Thus, with this increase in inflammation to the bone, helping with growth or remodelling, the nerves are responding and letting the brain know. This might feel painful!
How interesting that this bone metabolism occurs more during the dark hours. Our children truly can shoot up overnight!
This is just one example as to why pain might be worse at night. As I wrote earlier, there are many other reasons for pain, not just a bone fracture. So, if you are suffering some pain and are unsure as to why, get it investigated by having a discussion with your Doctor or Physiotherapist.
Dimitri, P., & Rosen, C. (2016). The central nervous system and bone metabolism: an evolving story. Calcified tissue international, 1-10.