The arm hurts. The neck decides: Cervical root pain as a mechanical decision problem

Arm pain of cervical origin is usually taught through four dermatomal maps. This educational analysis argues that the map is only the starting hypothesis. In a study of 66 patients with cervical radicular pain, 69.7% had pain that did not stay within the dermatome of the involved root (Murphy et al., 2009). Three further bodies of evidence turn the examination into a mechanical decision: foraminal area changes measurably with neck position; a four-test cluster shifts the probability of radiculopathy, with an independent validation published in 2026; and common exercises can each be read as a force vector with a dose and a stop rule. The analysis closes with a five-step sequence for clinicians (screen, localise, test, choose the vector, dose and re-test), set against population base rates for recovery, recurrence and surgery.