The location of your pain often provides useful a useful set of clues to understanding your underlying diagnosis, but there are sometimes traps that need consideration.
If you burn yourself, it’s pretty obvious what you’ve done. You can easily localise the site of injury. The sensation of pain provides immediate information that localised tissue damage has occurred in the region of the burn. Pain is frequently felt at the site of an injury, and the location is therefore a useful tool in your injury assessment. Tenderness on the bone of the outside of the ankle might represent a fracture, whilst tenderness below the bone might represent a ligamentous injury. Mapping the site of tenderness by palpation (pressing) is a common and relatively accurate method of examination used for diagnosis for many injuries.
In some instances however, the location and cause of your pain may not be as easy to evaluate. Deep structures, such as the hip joint, often produce pain that is often more difficult to localise. Even in thin people, you certainly can’t easily press on the hip joint cartilages to see if they are tender. Despite this, most parts of your body when injured will produce characteristic patterns of pain that can assist in making a diagnosis. For example, pain from hip joint arthritis will often be felt in the middle part of the groin.
Pain however is not always located directly at the site of injury. Pain located some distance distant from the site of injury in fact is very common for some conditions. There are two main types of pain that is felt some distance away from the site of injury – radicular pain and referred pain.
Most people are familiar with radicular pain. Sciatica is an example. Radicular pain is where a nerve root (typically as it exits the spinal column) is compressed. Causes for nerve root compression might include collapse of an intervertebral disc, with the deformed disc causing compression. Pain from a compressed nerve root is felt in the distribution of skin where the nerve normally provides sensation. The body map of skin sensation from individual nerve roots is known as a “dermatome map”. By assessing the distribution of a person’s pain and then comparing this to the dermatome map, your doctor can diagnose which nerve is being compressed. Compression of the L5 nerve root at the level of the spine can therefore be diagnosed by the presence of pain and numbness in the outer calf and foot. Pretty neat eh. Except of course if you’re the one suffering from sciatica.
Referred pain is a little different. Referred pain is the brain’s inability to work out where the pain is coming from. Think of this analogy. You are at the top of a mountain and want to get a message to the valley below. With cunning ingenuity, you place a message in a bottle (biodegradable of course) and put it in a stream. When your bottle does indeed successfully arrive at it’s destination, and your buddy opens it up to read the message within. “Help me, I’m stuck on top of the mountain !” it reads. But where did the bottle come from ? Unbeknown to you, by the time your mountain stream reached the valley, it had already combined with another stream – only this stream arose from the adjacent mountain to the East. From the valley below, your buddy therefore can’t be sure if the message originated from the east or the west mountain peaks.
Tricky situations in the evaluation of pain are common. A classic example is in the evaluation of a patient with knee pain. Pain located about the knee could be from the injury to knee joint itself (direct pain), compression of the L3 nerve root in the spine (radicular pain) or alternatively be caused by an arthritic hip joint (referred pain). Any of these options could explain pain about the location of the knee joint. Your doctor will therefore need to obtain more information to clarify the correct diagnosis – additional features based on your description of the pain, your physical examination findings and tests such as X-Ray will be required. Sometimes establishing a diagnosis requires a bit of detective work – the answer is not always as simple as it would first appear. If the decision to perform an operation hinges on a correct diagnosis, your doctor will spend some time making sure they’ve got it right.
But there is another confounding factor further complicating the situation. When the stream finally delivers the bottle containing your plea for rescue to your buddy, you might argue that at least he can now narrow down the search to one of two mountain ridges. Yes, this is true, but only if he was lucky enough to receive the message in the first place. What if you placed the bottle in the stream on the other side of the mountain face ? What if you placed the bottle in the correct stream, but it got snagged on a tree and never reached the intended destination ? The absence of a rescue note does not imply that all is well. Likewise, even though many joints have typical patterns of referred pain, there is a degree of variability between different people. Often not all the typical “text book” features will be present at once.
Pain is sometimes complex. Sometimes your treating clinician will be uncertain because conflicting data exists and more information may required to be more certain of your diagnosis. This is not a sign of your doctors incompetence, but a reflection of their attention to detail and personal humility. Whilst it may be frustrating at times being sent for tests to further evaluate your condition, a good clinician will typically only recommend treatment after a clear diagnosis has been established. Depending on your condition, the diagnosis may be straight forward. In more complex situations however, more careful consideration is required and the process to establish a diagnosis is more challenging.
This information has been written by A/Prof Patrick Weinrauch for the purposes of patient education. The details provided are of general nature only and do not substitute for professional recommendations based an individual clinical assessment. ©
A/Prof Patrick Weinrauch is an Orthopaedic Surgeon and the Director of Recovery Medical. Patrick, after repeatedly observing that better results were reliably obtained in those patients who were more optimally prepared for surgery, developed Recovery Medical to assist people in their preparation and post–surgical recovery.