Many theories have been advanced to explain the final neck shaft angle in the developing proximal femur. Muscle spasticity and delayed weight-bearing are the postulated causes of the development of the valgus deformity in patients with neuromuscular disease. Three patients with coxa vara exhibited some degree of spasticity and delayed weight-bearing. In spite of this, each child developed a varus rather than a valgus hip deformity. Existing theories seem not to adequately explain the development of the final neck shaft angle.