<p>The thoracolumbar fascia (TLF), a complex connective tissue structure, is gaining importance in back pain research. The TLF is important for force transmission, proprioception, and core stability. Histology reveals rich sensory innervation, particularly by nociceptive nerve endings. In patients with back pain, the following changes to the TLF have been observed: thickening of the posterior layer; reduced shear mobility between the two lamellae of the posterior layer; and enhanced pain sensitivity upon mechanical, chemical, and electrical stimulation. Animal experiments indicate that fascial lesions and mobility impairments can cause structural alterations. In addition, neuroplastic changes and increased nociceptive innervation have been observed. Herein, it is discussed whether these changes reflect the primary cause or secondary consequence of back pain. Three hypotheses are presented: primary fascial pathology, secondary adaptation, and bidirectional interaction. Clinical implications include targeted evaluation of the TLF for diagnosis and treatment. Manual techniques, sport therapeutic interventions, and new approaches such as extracorporeal shockwave therapy could contribute to treatment. Further research, particularly longitudinal studies, is required to improve the understanding of pathomechanisms and develop treatment strategies. Current results underscore the importance of placing increased focus on the TLF for both diagnosis and treatment.</p>