Analgesic Limits and the Central-Gain Seam: What Is Routed Out and Why (Results, Not Failures)

The central-gain lever (L3) is real but is OWNED by neuro / mind and is reached only as a named seam, never re-emerged here; the opioid lever is outside the non-opioid logic entirely. Exertional muscle pain has no discrete structural lesion to cross-check, and neuropathic and fibromyalgia pain are routed to sibling volumes — results stated as scope, not failures.

This page states what the analgesic axis does NOT claim. L3 (reduce the downstream gain) lowers the signal on the shared substrate, but central gain is a neuro / mind property; this volume cites it as a seam and does not re-emerge central pain (single source of truth). The opioid descending / μ lever is outside the non-opioid three-lever logic; exertional muscle pain is graded DIRECTION-only because there is no discrete contact-loss lesion to cross-check; and neuropathic pain, fibromyalgia and central sensitisation are routed to sibling volumes, exactly as in the out-of-class register (§20).

L3 central gain: a seam, not re-emerged

The third lever reduces the downstream gain that amplifies a crossing into a perceived signal. On the shared substrate that lowers the signal monotonically, so the lever clearly exists. But central gain (dorsal-horn and descending modulation, central sensitisation) is a property of the neuro / mind volumes, not of load-bearing matter.

So this volume names L3 as a SEAM to neuro / mind and stops there — it does not re-emerge central pain machinery (single source of truth). Gabapentinoids and SNRIs (duloxetine) are the L3 anchors, owned at that seam. This is the same discipline that routes fibromyalgia and neuropathic pain out (§20).

The opioid lever is out of the non-opioid logic

Opioids raise central inhibitory tone through a separate descending / μ-receptor lever. That is a fourth lever, outside the non-opioid three-lever technique, and is not modelled here. Where opioids are clinically first-line (e.g. cancer bone pain, §27), the non-opioid levers are stated as adjunctive.

Exertional muscle pain: DIRECTION only (honest partial)

Exertional and overuse muscle pain (the sarcopenia / myopathy context) does have an L1 and L2 lever, and both lower the crossing rate by direction on the MYOD1-grounded substrate. But there is no discrete structural contact-loss lesion to cross-check, so the coupled-versus-decoupled discriminant of §27 cannot be run here.

It is therefore graded as a DIRECTION-only result with no structural cross-check — logged, not dropped, exactly like the secondary entries elsewhere in this volume. L2 anchor: graded exertion / activity pacing.

Routed out (single source of truth)

Neuropathic pain, fibromyalgia and central sensitisation syndromes are not musculoskeletal-mechanism diseases; they are routed to sibling volumes via the named seams, never re-emerged here. The analgesic axis stays strictly inside the load-bearing class: it treats the nociceptive drive that this volume’s own mechanical diseases generate, and cites everything else.

That boundary is the point. The contribution is to show that, for the diseases this volume owns, the inherited three-lever technique lands cleanly — L2 in scope and convergent, L1 in scope and decoupled, L3 and opioids honestly out.