Pathophysiology of non-specific arm pain

Background: Non-specific arm pain (NSAP) is a vague clinical entity which may constitute up to 53% of work related upper limb disorders. The pathophysiology of NSAP is poorly understood with hypotheses ranging from disturbance of muscle function and neuropathic arm pain to central sensitization. Objectives: The purpose of this review was to investigate the current level of evidence to support three main classifications of pain (peripheral neuropathic pain, nociceptive pain and central sensitization) in NSAP. Major findings: There is evidence in the literature to support each of the three classifications of pain; however, this evidence is weak. No one classification of pain is better supported than another. It is also likely that overlap exists between pain classifications which present in NSAP. Conclusion: Different pain classifications are likely to exist in NSAP and indeed may co-exist. In the absence of definitive support for one classification over another, clinicians should be encouraged to perform thorough pain assessments in individuals with NSAP in order to optimize clinical decision making.