Referred pain is a phenomenon where pain is felt in a different part of the body from where the actual injury or problem exists. It occurs because the nervous system can sometimes interpret signals from internal organs or structures in a way that makes the brain perceive the pain as originating from a different location.
In the case of your shoulder hurting when your neck is injured, this could be due to the complex network of nerves in the body. The nerves that supply sensation to different parts of the body often overlap or converge at certain points along the spinal cord. When there is an issue or injury in one area, such as the neck, the brain may interpret the signals from the affected nerves as pain in another area, such as the shoulder.
For example, if there is a problem with the nerves in your neck, such as a pinched nerve or muscle strain, the brain may interpret the signals from those nerves as pain in your shoulder. This can lead to the sensation of shoulder pain even though the source of the problem is actually in your neck.
Referred pain can sometimes make it challenging to identify the exact source of pain, as the location where you feel the pain may not necessarily correspond to the location of the underlying issue. However, healthcare professionals can often use other symptoms, physical examinations, and diagnostic tests to determine the true cause of the pain and develop an appropriate treatment plan.