By Dr David Tiberio
As the gait cycle progresses, the lead leg becomes the trail leg. But there may be an advantage to consider what is happening to the trail leg at the same time the lead leg is going through its REAL bone and RELATIVE joint motions. Since the previous blogs used the right leg as the lead leg, this blog we will focus on the left leg when discussing the trail leg. When the right foot strikes the ground, the three RELATIVE joint motions occurring in the trail / left hip are extension, abduction and (surprisingly) internal rotation. Knowing which REAL bone motions create the 3 RELATIVE joint motions is important because both propulsions off the trail leg and loading of the lead leg will be affected by trail hip dysfunction.
The extension of the trail hip (left hip in this example) in the sagittal plane is created by the REAL bone rotations of extension of the femur and anterior rotation of the pelvis. The pelvis rotation is subtle but important as described in the lead hip blog. There may be some very slight differences between the two ilium bones because of sacroiliac joint motion, but the anterior rotation of the pelvis that occurs at the lead hip is the same REAL bone anterior rotation that is occurring in the trail hip. Anterior rotation by itself would create RELATIVE hip flexion. An appreciation of what creates the REAL bone extension of the femur, and how that leads to RELATIVE hip extension is critical.
As the body moves over the foot, the pelvis translates (slides) forward. This translation “drags” the proximal end of the femur forward. With the foot still in ground contact, the distal end of the femur moves forward, but not as much. The forward position of the proximal end creates REAL extension of the trail leg femur. Since we usually think of extension as the distal end of the femur moving back, it is a challenge for all of us to recognize that the proximal end moving forward is also REAL extension of the femur. Therefore, the anterior translation of the pelvis creates the RELATIVE hip joint extension, and it is this joint extension that lengthens the hip flexors in preparation for swinging the trail leg forward.
Understanding how hip extension in gait is created brings to light the practical limitations of checking hip extension prone on a table. Although movement practitioners can get some indication of joint restrictions, the REAL bone motions occurring in response to the physical forces are missing. The Chain Reaction Biomechanics of gait require that an authentic assessment include having: 1. the body upright relative to gravity, 2. the foot on the ground, 3. the opposite leg moving forward, and 4. the motion created by the momentum of the centre of mass moving forward.
In 3DMAPS the Right Anterior Chain Analysis Movement creates RELATIVE left hip extension by replicating the sagittal plane REAL bone motions of the pelvis and the femur that occur in the trail hip. The Mobility Movement indicates the available REAL bone and RELATIVE joint motions. As the right foot lunges anteriorly, the pelvis translates forward. The posterior overhead arms swing creates an additional challenge to the left hip to demonstrate RELATIVE joint extension. The Anterior Chain Stability Movements provide insight into the body’s control of the hip extension.
3DMAPS provides all movement specialists a set of powerful tools to determine the ability of the client to produce the required REAL bone motions. The value of 3DMAPS is that in addition determining the Mobility and Stability of the RELATIVE hip joint motions, the integrated movement approach will indicate other joint impairments in the Chain Reaction that can be the causes of dysfunction during gait and any other functional activity.