Which of the following is NOT a major subluxation theory?

The response identifies Musculoskeletal Discomfort as the option that does not represent a major subluxation theory. This is justified because Musculoskeletal Discomfort refers more to the symptoms or effects experienced by individuals due to various conditions, rather than a theoretical framework or mechanism explaining how subluxations occur or affect the body.

The other options—IVF Encroachment, Altered Sensory Input, and Spinal Cord Distortion—are recognized subluxation theories within chiropractic practice. IVF Encroachment explains how subluxations can lead to nerve compression within the intervertebral foramen, potentially impacting nerve function. Altered Sensory Input highlights how subluxations may affect proprioception and sensory feedback, influencing the body's awareness of its position. Spinal Cord Distortion refers to changes in spinal alignment that can affect the spinal cord and neurological function.

These theories provide a foundation for understanding how subluxations can influence health, while Musculoskeletal Discomfort does not fit into this theoretical framework in the same way because it is primarily associated with the physical sensations of pain or discomfort rather than a causal theory of subluxation itself.