Chronic pain represents one of the most complex challenges of contemporary medicine. This narrative review critically analyzes the limitations of the traditional biomedical model in addressing chronic pain, highlighting how its reductionist vision is inadequate to effectively understand and treat this condition. The conceptual evolution of pain from a simple symptom to a codified "disease" is examined, highlighting the incongruities of this approach. The contribution of the bio-psycho-social model is discussed, recognizing its merits but also its applicative limits. Finally, the integration of the functional model, derived from functional medicine, is proposed as a complementary element that could fill the existing gaps, paying greater attention to nutritional and environmental factors and to the mesenchymal matrix as the biological "terrain" of chronic painful diseases. This review suggests the evolution towards a "bio-psycho-functional and social" model for a more complete understanding and management of chronic pain.