Where Osteoarthritis Pain Comes From: Mapping Substance P and CGRP Neuropeptides Across Joint Tissues

What the researchers found

Nociceptive free-nerve endings and substance P-staining nerve fibers were identified in multiple joint structures: accessory ligaments, synovium (joint lining), subchondral bone (bone beneath cartilage), menisci, and periosteum (bone covering). Calcitonin gene-related peptide (CGRP) was also present in these tissues.

The vasculature may contribute to pain through vasospasm or ischemia, though this mechanism remains unproven. Joint denervation procedures can relieve pain — confirming that articular nerves carry pain signals — but cannot pinpoint the specific tissue source. The review concludes that the primary anatomical source of OA pain remains unclear and likely varies between patients and joints.

Why it matters

Osteoarthritis affects over 500 million people worldwide, and pain management is often inadequate because treatments aren't targeted at the specific tissue source generating pain. Understanding where neuropeptides like substance P and CGRP are concentrated in joint tissues could lead to more precise pain treatments — for example, targeted nerve blocks, localized anti-CGRP therapies, or tissue-specific interventions rather than systemic painkillers.

How the study worked

This is a narrative review focused on studies examining nociceptive innervation of synovial joints, with particular emphasis on the distribution of substance P and calcitonin gene-related peptide in joint tissues. The review was written for educational purposes, aimed at improving the teaching of pain anatomy in medical school courses.

What this study cannot tell us

This is a narrative review for teaching purposes, not a systematic review with comprehensive literature search methodology. It was published in 2014 and may not reflect more recent research on joint nociception. The review acknowledges that the primary pain source in OA remains unidentified, limiting its ability to provide definitive conclusions. Individual variation in pain sources adds complexity that cannot be resolved by anatomical mapping alone.

How to read the evidence

This is a narrative review intended for educational purposes, not a systematic review or primary research study. It synthesizes existing knowledge about nociceptive anatomy without new data or formal evidence grading methodology.

When this study was published

Published in 2014, this review is over 10 years old. Since then, research on neuropeptide involvement in joint pain has advanced, and CGRP-targeted therapies have become clinically available for migraine, raising interest in applying similar approaches to osteoarthritis.

The bigger picture

Substance P and CGRP are the same neuropeptides now targeted by breakthrough migraine therapies (CGRP antibodies like erenumab). Their prominent role in joint pain suggests similar targeted approaches could eventually be applied to osteoarthritis. The review also highlights a fundamental gap in medical education — anatomists and clinicians still lack a complete understanding of how joint pain is generated, which has held back the development of more effective treatments.

Questions still open

• Could CGRP-targeted therapies (like those used for migraine) be adapted to treat osteoarthritis joint pain?
• Do the relative contributions of different joint tissues to pain change as OA progresses from early to advanced stages?
• Would imaging techniques that visualize substance P or CGRP distribution help personalize pain management for individual OA patients?

Common questions

Read the original research

The anatomy of osteoarthritic joint pain.

Clinical anatomy (New York, N.Y.), 27(3), 451-4

Citation

Witt, Kevin L; Vilensky, Joel A. (2014). The anatomy of osteoarthritic joint pain.. Clinical anatomy (New York, N.Y.), 27(3), 451-4. https://doi.org/10.1002/ca.22120