The seemingly logical presumption that pain is due to injury at the site of the pain can be an incorrect conclusion. Many times a painful area of the body is not the real location of injury for that pain.
While it’s true that sometimes the cause of a pain is the result of some other area at fault – knee pain due to poor mechanics in the foot for example – the knee pain itself comes from the knee.
However, at times knee pain itself does not come from the knee; it may be a hip injury that is felt at the knee, where there is actually nothing wrong with the knee. This is called referred pain.
Referred pain is common. It’s defined as pain from a malfunctioning or diseased area of the body, perceived in another area, often far from the origin.
Neuroscientists still don’t know precisely which anatomical connections are responsible for referred pain. The prevailing explanation is based on interconnected sensory nerves.
Referred pain happens when sensory nerve fibers from one region of the body and sensory nerve fibers from another region of the body (be it skin, muscle, or an organ) happen to converge at the same level of the spinal cord.
The best known example is pain experienced during a heart attack. Nerves from damaged heart tissue convey pain signals to spinal cord levels T1-T4 on the left side, which happen to be the same levels that receive sensation from the left side of the chest and part of the left arm. The brain isn’t used to receiving such strong signals from the heart, so it interprets them as pain in the chest and left arm.
For example, it is unlikely but possible that shoulder pain is a sign of a problem in the liver, gall bladder, stomach, spleen or lungs. Conditions as diverse as liver abscesses, gallstones, gastric ulcers, splenic rupture, pneumonia or pericarditis can all cause shoulder pain.
It is also common for a low back injury to create referred pain that radiates into the groin, buttock and upper thigh. Referred pain from the back to the legs often moves around, and rarely radiates below the knee.
It is very common for referred pain in the leg to be confused with a damaged nerve in the low back or sciatica. Obviously the distinction between referred pain and sciatica is critical as the treatment of the two conditions varies considerably.
The pain felt can often feel so ‘real’ that both the therapist and the patient are mislead as to the origin of the pain. Unfamiliarity with referral pain patterns can lead to misdiagnoses as well as inappropriate treatments, by both the patient and the health care practitioner.
This is why your chiropractor is so careful with your history and physical examination. Your chiropractor is specially trained to recognize pain referral patterns, and how to determine the origin and nature of the pain of your complaint.
Referred pain is a symptom of a problem and will diminish as the primary area of complaint is treated.