How Referred Pain Makes Arthritis Diagnosis Difficult

Source of the pain may be different from where it it felt

Pain in a knee
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Diagnosing arthritis can sometimes be a trickier than it seems. While arthritis is characterized by inflamed, swollen, and painful joints, the pain itself can often be a red herring.

This is because nerves can sometimes become "pinched" between swollen joints and send pain signals through the entire nerve string. This can happen either intermittently, such as when a person walks, or be persistent as the nerve becomes permanently trapped between the two joint surfaces.

When this happens, the pain doesn’t always radiate from the point of compression. Instead, it may only be felt in distant parts the body, far away from the point of compression.

We called this referred pain.

Understanding Referred Pain

Referred pain can cause confusion and delay diagnosis in people with arthritis. A person with persistent knee pain, for example, may actually have hip osteoarthritis. Another with upper back pain may be suffering from arthritis in the joints of the neck.

While rheumatologists and orthopedic specialists can often identify referred pain on early diagnosis, other doctors may not. In some cases, the pain can be misattributed to everything from muscle strain to emotional stress. In the worst-case scenario, people may be led to believe that it’s "all in their head" or be exposed to investigations or treatments that are entirely unnecessary.

Referred pain can be especially difficult to diagnose as the pain signals travel along unexpected pathways.

It is unlike a radiating pain in which the pain follows a common path (such as when a herniated disk causes pain down the back of the leg or hitting your funny bone triggers a jolt from the elbow to pinky finger). A referred pain, by contrast, is defined by a disassociation between the source and location of the pain.

Referred Pain in Arthritis

Referred pain in arthritis is a complex neurological process caused by the interconnected and sometimes scattered network of nerves. Based on how a nerve is compressed, the location of the pain can often shift by location or sensation. While referred pain most often vague and non-specific, it can sometimes be sharp and clearly defined.

Examples of this include:

  • Arthritis in the small joints of the neck can refer pain into the outer arm or shoulder blade.
  • Osteoarthritis in the hip can refer pain into the groin, lower thigh, or below the knee.
  • Arthritis in the spine can refer pain to the buttocks and thigh, where it can often be mistaken for sciatica.

If the doctor is unable to make the connection between the referred pain and the arthritis, a person may end up being X-rayed on the knee for a hip problem or given cortisone shots that have no effect.

Diagnosis

Diagnosing arthritis in the face of a referred pain can often feel like a wild goose chase. In the end, there is often no easy way to "connect the dots" between the source and location of the pain, at least not by neurological means.

In most cases, a doctor will need to take an extensive patient history and weigh factors like age, mobility problems, family history, and repetitive motion injuries to assess whether there is the likelihood of arthritis.

If X-rays are inconclusive and presumptive treatment provides no relief, you will likely be referred to a specialist based on your symptoms. An experienced orthopedist may be able to recognize that the referred pain pattern and focus the attention on the source, rather than location, of the pain.

An X-ray or magnetic resonance imaging (MRI) scan may provide evidence of arthritis, while an injection of cortisone into the site can provide confirmation if the referred pain significantly improves.

Sources:

Hunter, J.; MacDougall, J.; and Keefe, F. "The symptoms of OA and the genesis of pain." Rheum Dis Clin North Am. 2008; 34(3):623-43. DOI: 10.1016/j.rdc.2008.05.004.

Kidd, B. "Mechanisms of Pain in Osteoarthritis." HSS J. 2012; 8(1):26-8. DOI: 10.1007/s11420-011-9263-7.

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