OA is a condition long thought to be characterized by damage to the cartilage and bone; however, as with many other pain diagnoses, there is frequently little correlation between damage seen on radiographs and the amount of pain that patients experience.
One study analyzed data on almost 7,000 patients from the National Health and Nutrition Examination Survey (NHANES I) and found that between 30% and 50% of OA patients with moderate to severe radiographic changes were asymptomatic, and 10% of those with moderate to severe pain had normal radiographs or only mild changes.39 Research is showing that many factors may contribute to this discrepancy, including the typical “wear and tear” of the disease, subacute levels of inflammation that can lead to peripheral sensitization, and, in some patients, a centralized pain component.40 The patients with more centralized pain often have pain that is disproportionate to radiographic evidence, as well as more somatic symptoms, such as fatigue, sleep disturbance, and memory issues.41
Treatment should be multimodal and include interventions targeted at halting the progression of damage as well as palliation of pain. All treatment plans for OA should also include exercise, weight reduction, and self-management, in addition to pharmacologic interventions, to reduce both the micro-inflammation and the centralized pain component (when present). Intra-articular injections of various types have been studied with some having more efficacy in pain reduction and functional improvement than others.42-45 See Table 3 for a summary of evidence-based treatment options.42-61
Low back pain: a mixed pain state
Low back pain (LBP) has been recognized as a mixed pain state for quite some time. While some patients may experience purely nociceptive and/or neuropathic pain, most cases are nonspecific, with patients experiencing varying degrees of nociceptive (myofascial LBP), neuropathic (lumbar radiculopathy), and central sensitization pain.62,63 Evidence for centralized pain is demonstrated in studies showing hyperalgesia, augmented central pain processing, involvement of the emotional brain, and delayed recovery influenced by poor coping strategies.64-67
When developing a treatment plan for a patient with chronic LBP, remember that the pain derives from a complex combination of pathophysiologic contributors. Identifying where a patient lies on the pain centralization spectrum can help you tailor treatment.
In one study of 548 patients presenting to a tertiary pain clinic with primary spine pain diagnoses, 42% met diagnostic criteria for fibromyalgia.68 Compared to criteria-negative patients, these patients tended to be younger, unemployed, and receiving compensation; they had greater pain intensity, pain interference, and used stronger words to describe their neuropathic pain, as well as having higher levels of depression/anxiety and a lower level of physical function.
Because LBP is a condition with high prevalence and associated disability, many clinical boards have created guidelines for management. These guidelines tend to vary in the strength of evidence used, and the extent to which they are followed in clinical practice remains largely unknown. Recommendations frequently discourage the use of ultrasound/electrotherapy, but many encourage short-term use of medications, supervised exercise therapy, CBT, and multidisciplinary treatment.
Guidelines tend to differ most widely with regard to recommendations for spinal manipulation and specific drug therapies.69 The classes of drugs that may be most useful when centralized pain is present include the SNRIs and the alpha 2 delta calcium channel ligands.4 See Table 4 for a summary of evidence-based treatment options.70-89
Case 1 Lola is started on amitriptyline 25 mg at bedtime, which improves her fatigue and cognitive symptoms. During monthly office visits, her FPP educates her about the pathophysiology of fibromyalgia and uses motivational interviewing to get her slowly moving and increasing her activity level. She is weaned off the gabapentin previously prescribed, as her symptoms stabilize and improve.
Case 2 Matt is sent for a steroid injection, which decreases his pain temporarily. During this time, he begins physical therapy; slowly, with increased movement, his function improves. A trial of duloxetine provides pain relief; that combined with intermittent NSAIDs has allowed Matt to maintain his function and his job.
Case 3 Because Keith was only taking the narcotics intermittently and wasn’t certain they were helping, CBT was sufficient to wean him off the medication without any worsening of his pain in the process. By participating in physical therapy, he has learned how to perform certain tasks at his job without pain or injury. He uses NSAIDs as needed for pain.
The authors thank Drs. Daniel Clauw (University of Michigan, Ann Arbor) and Martha Rumschlag (Providence Family Medicine Residency Program, Southfield, Michigan), for their valuable contributions to this article.
