Scoliosis, hip subluxation and hip dislocation in non-ambulant children with CP are important considerations for clinicians. In this paper, we propose a pathophysiological hypothesis to explain the process of hip dislocation based on the following chain of events: hip dislocation associated with progressive pelvic dissymmetry, lumbar spine hyperlordosis, and finally lumbar scoliosis with convexity contralateral to the dislocated hip. Our hypothesis is the psoas and ilio-psoas muscles are primarily responsible for these changes. First, the ilio-psoas muscle shortens. Second, the coapted hip becomes the center of rotation for the movements in all three planes of space. Third, the process of subluxation with pelvic dissymmetry begins and becomes irreversible. Fourth, the psoas on the dislocated side further shortens, and, because of its insertion point on the femur pulls on the lumbar spine. The psoas thus tilts the spinal column and accentuates the lordosis. Despite bone maturation, this aggressive form of scoliosis continues to progress.
