Chronic pain for rheumatological disorders: Pathophysiology, therapeutics and evidence

Pain is the leading reason people seek orthopedic and rheumatological care. By definition, most pain can be classified as nociceptive, or pain resulting from non-neural tissue injury or potential injury, with between 15% and 50% of individuals suffering from concomitant neuropathic pain or the newest category of pain, nociplastic pain, defined as "pain arising from altered nociception despite no clear evidence of actual or threatened tissue damage, or of a disease or lesion affecting the somatosensory system." Pain classification is important because it affects treatment decisions at all levels of care. Although several instruments can assist with classifying treatment, physician designation is the reference standard. The appropriate treatment of pain should ideally involve multidisciplinary care including physical therapy, psychotherapy and integrative therapies when appropriate, and pharmacotherapy with non-steroidal anti-inflammatory drugs for acute, mechanical pain, membrane stabilizers for neuropathic and nociplastic pain, and serotonin-norepinephrine reuptake inhibitors and tricyclic antidepressants for all types of pain. For nonsurgical interventions, there is evidence to support a small effect for epidural steroid injections for an intermediate-term duration, and conflicting evidence for radiofrequency ablation to provide at least 6months of benefit for facet joint pain, knee osteoarthritis, and sacroiliac joint pain. Since pain and disability represent the top reason for elective surgery, it should be reserved for patients who fail conservative interventions. Risk factors for procedural failure are the same as risk factors for conservative treatment failure and include greater disease burden, psychopathology, opioid use, central sensitization and multiple comorbid pain conditions, poorly controlled preoperative and postoperative pain, and secondary gain.