There are several ways that our body experiences pain. When our body has been in pain for a long period of time it becomes even more sensitive to pain. This is called ‘wind up’. Understanding why this happens lets us see why treating arthritis can be tricky.
If chronic pain isn’t noticed, or treated, changes start to occur in the nervous system
Repeated pain signals to the parts of the brain that receive them (receptors) can cause these receptors to become “wound -up”, or overstimulated
This leads to the brain interpreting feelings that shouldn’t be uncomfortable as painful
Eventually this over-stimulation starts to change the chemical balance in the brain; this is central sensitisation
What are the different types of pain?
This pain arises from the nerve endings (peripheral nerves) when they detect inflammation
This is pain arising as a direct result of nerve damage
This is pain arising most commonly from damage at the level of the spinal cord, but also the brain and brain stem.
What type of pain do dogs with arthritis have?
Animals with pain from long-term arthritis will have nociceptive pain from the inflammation. Many arthritic dogs also have neuropathic (nerve) pain, as the nerves become pinched by swollen joints or new bone growth. If this pain is not addressed, it may lead to central pain, as pain signals are constantly being sent to the brain causing “wind up”. Eventually, this leads to chemical changes within the brain. This process is known as central sensitisation.
Central Sensitisation can lead to:
Allodynia -feeling pain when you wouldn’t normally expect to, such as when being touched lightly.
Hyperaesthesia -feeling painful things even more intensely than expected.
This heightened state of pain awareness has a serious effect on a dog’s quality of life, and makes treating arthritis more difficult.
Why is it important to understand this?
It may seem complicated, but understanding central sensitisation leads to an understanding that:
Recognising long-term pain as early as possible is really important so we can start to manage it as soon as possible
We can recognise long-term pain when we look out for the subtle signs
These symptoms may come and go, but all the while the risk of central sensitisation increases, so it’s important to take them seriously
If your dog has central sensitisation, there are still things we can do, and all animals deserve pain relief. It may take your vet prescribing more than one type of treatment, and your dog may take some time to feel comfortable again, but working with your vet is the best thing to do.