07/11/2025
👉(A) Ideal lumbar posture and lumbar lordosis associated with a normal length of the psoas and lumbar erector spinae and
👉(B) altered biomechanical alignment of stance associated with tightness of the anterior hip capsule and iliopsoas. Under normal conditions, alignment of the acetabulum and femoral head is such that compression and shear stresses are optimally distributed protecting the hyaline cartilage and subchondral bone. Moreover, resting muscle tonus is balanced between hip flexors and extensors in a way that the metabolic cost to maintain balance is minimized. With plastic shortening of the anterior hip capsule and hip flexor muscles, more energy, i.e., activation of hip extensors, is needed to control a “quiet” bipedal stance. Increased isometric muscle activation simultaneously increases joint compression stress, which is poorly distributed because of the misalignment of the acetabulum and femoral head secondary to a chronic hip flexion pose.
