July 21, 2020
By: Jack Sproul, MD, Orthopaedic Surgeon at Carolina Pines Regional Medical Center
Some time ago I was standing outside after earlier doing a lot of lifting and bending. I had the sudden onset of pain in my foot. Puzzled as to how or why it was there, I took my shoe off and found no place that I pushed was tender. After a period of thought, I began laughing. The pain was referred from my back, which had been a known problem. I realized I spend everyday of my work week convincing people that their pain is in fact referred from somewhere else, but when it happened to me I was convinced my foot was the source of the pain. It is very human that when we feel pain, we expect that the pain is generated at the area where it is felt.
Referred pain is when pain is generated in one area and felt in another. In orthopaedics the pain is often present in either the arms or legs but is generated in either the neck or lower back. Interestingly, referred pain always goes out away from the center of the body, in other words, the pain can be referred from the neck to the shoulder but not from the shoulder to the neck. Referred pain patterns are constant among humans, making these problems a bit easier to diagnose. We feel all pain in our brain, our center of consciousness. For example, pain sensors in the foot are transmitted by nerves which go into the spinal cord and then up into the brain where they reach consciousness. If the nerve is pinched en route to the brain (such as where the nerve enters between the vertebrae of the lower back), it may send a signal to the brain which is interpreted as pain at the foot, even though the signal originated in the nerve at the lower back. This is commonly referred to as sciatica.
Sometimes the mechanism of referred pain is not as clear. Most people are familiar that sometimes with a heart attack people will have pain only in the left arm or jaw. Obviously, the heart is in neither of these locations, but the brain perceives the pain as coming from these areas. In orthopaedics, pain from degeneration of discs (the flexible spacers in between the vertebrae) or the small facet joints in between the vertebrae are often perceived elsewhere. If the spine degeneration is in the neck, the pain is referred to the shoulder or arm. If the spine degeneration is in the lower back, the pain is referred to the buttock region or thigh. This type of referred pain is independent from pinching of a nerve root. Interestingly, this type of referred pain does not typically go further than the elbow or knee.
Treatment of referred pain involves determining the source of pain. Doctors who treat pain often use written pain diagrams, where people mark on a body diagram where the pain is perceived. As these patterns are constant, evaluation of the source, often the cervical or lumbar spine, with X-ray or MRI may be helpful.
Not surprisingly, treatment of the neck or treatment of the lower back is the way that we manage pain referred to the arms or legs. An injection into the shoulder when the pain is generated from the neck is somewhat like replacing your TV when the problem was in the cable or TV station. Neck and lower back are particularly prone to degeneration because they have moving parts. The thoracic spine and the sacral spine have minimal motion. The thoracic spine has ribs which limitmotion, the sacrum, at the back of the pelvis, has fused vertebra. Just like with machinery it is the moving parts that wear out. Treatment of the neck or lower back may involve physical therapy, injections or, if not helped by simpler methods, surgery.
To learn more about Orthpaedics at Carolina Pines, visit https://www.cprmc.com/orthopaedics-and-spine