The lower-crossed syndrome is a postural distortion syndrome affecting the lower kinetic chain (lumbopelvic hip complex, knee, and ankle). The lower kinetic chain is one of two basic parts of the musculoskeletal system that are controlled and innervated through the CNS. The muscles can often serve as “windows” to the function of the CNS.The CNS regulates 2 muscle groups: The tonic muscle group and the phasic muscle group. These muscle groups oppose each other in function. The tonic muscle group functions as a facilitator, the phasic muscle groups inhibition. Pain, pathology or adaptive changes in the system result in compensations or adaptations that lead to systemic and predictable patterns of muscle imbalance. This results in chronic pain and disability. In lower-Crossed syndrome, the pattern of muscle imbalances often leads to changes in movement patterns with hip extension, hip abduction, and trunk flexion. “Altered movement pattern” is a movement pattern in which a change occurs in the coordination of the muscle firing sequences for a specific group of muscles, facilitating a specific joint movement. The primary muscle responsible for specific joint movement may become weak and inhibited, causing a synergistic muscle/muscles to become hyperactive. As a result, a different sequence of muscular contractions occurs. This is a sign of muscle imbalance in the body because of muscular dysfunction.
Because the structural integrity of the lower kinetic chain is compromised in lower cross syndrome, abnormal distorting forces result in all structures within the kinetic chain. When any component of the kinetic chain is not working properly (tight or long muscles, reciprocally-inhibited muscles, adhesions, joint dysfunction), neuromuscular control is altered. This alteration may be observed with the patient sitting, standing, or walking.