The spine-pelvis-hip complex functions as 2 hinges that move in coordination in the sagittal plane. These consist of a posterior hinge (the lumbosacral junction), which flexes an average of 20° when a person sits from a standing position, and an anterior hinge (the hip joint), which flexes an average of 60° when a person sits. If the posterior hinge loses motion because of degenerative changes or lumbar fusion, the anterior hinge (i.e., the hip) must compensate with excessive flexion. Conversely, if the hip joint loses motion because of hip osteoarthritis, the posterior hinge (i.e., the lumbosacral junction) must compensate with increased motion, explaining why the majority of patients with hip osteoarthritis and concomitant back pain have resolution of the back pain after THA.
An excellent Picture. Can you tell us the source? Is it Open source and is it possible to use it?