A second neurologic model focuses more on the interrelationships of the peripheral and central nervous systems, their reflex patterns, and their multiple pathways. This model is particularly useful in managing patients with pain syndromes, such as back pain. Although controversy remains about the origin of back pain, much is known about the location and type of nociceptors and mechanoreceptors within the musculoskeletal system.⁶ The pain stimulus can originate in a number of tissues and be transmitted by peripheral afferent neurons to the spinal cord for integration and organization. Different neurons end in different laminae of the dorsal horn and synapse with interneurons that transmit information up and down the spinal cord, thus affecting other neuronal pools through propriospinal pathways. Transmission up the cord to higher centers can be through the fast or slow pain pathways. Pain is perceived in the brain, and stimulatory or inhibitory activities can enhance or reduce the pain perception. These processes are programmed through the brainstem and back down the cord to modulate activity at cord segmental level.

An understanding of the anatomy and physiology of the musculoskeletal system and nervous systems, particularly the spine and paraspinal tissues, is necessary to develop a therapeutic plan to manage the patient’s pain syndrome. A clear distinction must be made between acute pain and chronic pain. Acute pain is that which is best known to the clinician. It results from tissue damage, is well localized, has clear objective evidence of injury, and has a sharp pricking quality. There may be some lingering burning and aching. Acute pain responds well to treatment and abates when the tissue damage has resolved. Chronic pain persists despite the lack of ongoing tissue damage. It is poorly localized with no objective evidence present. It has a burning aching quality with a strong associated affective component. Changes have occurred in the central pathways and central endogenous control. It is unclear as to when chronic pain begins, but it is generally accepted that ongoing pain beyond three months results in central pathway changes. Acute and chronic pains respond differently to therapeutic interventions. Manual medicine has a role in the treatment of both acute and chronic musculoskeletal pain syndromes. In the acute condition, manual medicine attempts to reduce the ongoing afferent stimulation of the nociceptive process.⁷ If it is determined that muscle contraction and hypertonicity are primary factors, muscle energy procedures might be most beneficial. If it is believed that altered mechanoreceptive behavior in the articular and periarticular structure of the zygapophyseal joint is the primary factor, a mobilizing procedure with or without impulse might be more appropriate. The goal of manual medicine in the patient with chronic pain is to restore the maximum functional capacity of the musculoskeletal system so that exercises and increased activities of daily living can occur. It is difficult for a patient with chronic pain to undergo exercise therapy and reconditioning rehabilitative processes in the presence of restricted mobility of the musculoskeletal system.

The third concept within the neurologic model is that of dynamic stability. Recently, a large focus on trunk control and dynamic joint stabilization has immersed itself on the physical therapy and biomechanical literature.⁸ The primary tenet is a respect for the body’s utilization of neuromuscular “feedforward” neurologic mechanisms, to prepare it to accomplish a task, and “feedback” neurologic mechanisms, to prevent injury or strain in the case of unexpected perturbation. Dynamic stability of the spine relies on the interdependent relationship of active (muscular), passive (articular/ligamentous), and neuromuscular subsystems defined by Panjabi.⁹ The active subsystem component of most importance for dynamic stabilization is the muscles that control “neutral” joint position. These “stabilizer muscles are described as having the characteristics of being mono-articular or segmental, deep, working eccentrically to control movement, and having static holding capacities.”¹⁰ The passive subsystem consists of the articular surface, ligaments, and discs, which provide structural control, movement checks, and critical afferent kinesthetic information via its mechanoreceptors.¹¹ The neuromuscular subsystem relies on the central nervous feedforward control as well as feedback neurologic information from the active and passive subsystems. Although joint dysfunction resulting in musculoskeletal pain is often approached from the biomechanical model, there has been a significant amount of research suggesting an association with inhibition of the local stabilizers as well as deficits in feedforward and/or feedback neurologic mechanisms¹² and thus deserves a neurologic consideration.