Examining Unilateral Anterior Hip Rotation - First Cardinal Sign, SRLS
It is a fact the most common hip presentation is anterior rotation of the left hip with a level right hip. It is so common I call it normal. It is not good anatomical posture but it is normally what is seen in clinical practice.
Anterior rotation of the hip functionally adjusts leg length. Rotation about the SIJ in the Sagittal plane causes the head of the femur to move posteriorly and superiorly, pulling the leg upwards. If leg lengths are structurally even, such an action would cause a tilt in the pelvis and result in mild scoliosis toward the side demonstrating rotation.
The catch is, this is not what we see in clinical practice. We are presented with left sided anterior rotation but rather than the expected left leaning pelvic tilt and left leaning scoliosis, in virtually all cases I observe a right leaning condition. This can only happen if the right leg is structurally shorter than the left by an amount greater than the functional adjustment caused by the left hip’s anterior rotation.
I propose the observed unilateral hip rotation occurs when the contra-lateral leg is structurally short. We feel uncomfortable with the tilt through our pelvis caused by the structural imbalance. By some mechanism the hip of the longer leg unconsciously flops forward functionally shortening the longer leg. This is an anatomic adjustment reducing the leg length difference. Typically, we are not aware of the compensatory action. It feels more comfortable and it protects the spine. This is good but chronic hip rotation tightens the heavily bound ligamental structure and cartilage of the SIJ and can lead to other issues.
This proposal is supported by my observation the postural hip anomaly will resist attempts to normalise its position through treatment and rehabilitation exercise/stretching until an adjusting prosthetic wedge is inserted beneath the heel of the structurally short leg.
First published 13 May 2021 at