If you haven't read the other three blog posts related to this (how the body works as a unit and how foot and leg posture influence each other, how spine and shoulder posture influence each other), you can read them here and here and here.
In this blog post, I am going to continue the discussion of how the body works as a unit and specifically how the hip, pelvis, and spine influence each other. You will be able to understand and feel this relationship with 3 simple experiments...
In this blog post, I am going to continue the discussion of how the body works as a unit and specifically how the hip, pelvis, and spine influence each other. You will be able to understand and feel this relationship with 3 simple experiments...
 trunk and pelvis skeletal system |  trunk and pelvis with ligaments |  trunk and pelvis with deep muscles |  trunk and pelvis with all muscles |
The hips, pelvis, and spine are connected together via joints and the bones, ligaments, and muscles that control them. The basic movements that can happen at this joints are:
- Hip joint: flexion, extension, internal rotation, external rotation, abduction, adduction
- Sacroiliac joint (SI joint): very limited rotation and translation
- Pubic symphysis: very limited rotation and translation or shift
- Joints of the vertebral column: flexion, extension, rotation, lateral flexion
Let's look at the hip joint first. Your hip joint is a ball and socket joint where the head of the femur articulates with the acetabulum of the pelvis. The bones and joint surfaces are designed to match up where there is maximum surface area touching each other. The wisdom of this design means that if you change the position of your femur the pelvis will adjust (and vise versa) to maintain maximum surface area contact. You can experience this with an easy experiment.
Experiment 1: the femur and pelvis relationship
1. Stand up, point your feet straight ahead, and notice the position of your pelvis.
2. Then turn both feet out at a 45 degree angle which externally rotates your femurs and notice the position of your pelvis.
3. Then turn both feet in at a 45 degree angle which internally rotates your femurs and notice the position of your pelvis.
What did you notice?
When you turn your feet out you should notice your pelvis tilt backwards or posteriorly slightly and when you turn your feet in you should notice your pelvis tilt forward or anteriorly slightly. This is normal function of the hip joint. If you did not feel that happen or felt tightness, pain, or could not rotate your legs into these positions, this means you have dysfunction in your hips.
The opposite experiment you can do is tilt your pelvis and notice how that changes your femur position (rotation). When you tilt your pelvis anteriorly your femurs should rotate internally and when you tilt your pelvis posteriorly your femurs should rotate externally. (Again if that doesn't happen for you, it is a sign that you have hip dysfunction).
When you turn your feet out you should notice your pelvis tilt backwards or posteriorly slightly and when you turn your feet in you should notice your pelvis tilt forward or anteriorly slightly. This is normal function of the hip joint. If you did not feel that happen or felt tightness, pain, or could not rotate your legs into these positions, this means you have dysfunction in your hips.
The opposite experiment you can do is tilt your pelvis and notice how that changes your femur position (rotation). When you tilt your pelvis anteriorly your femurs should rotate internally and when you tilt your pelvis posteriorly your femurs should rotate externally. (Again if that doesn't happen for you, it is a sign that you have hip dysfunction).
It is important to remember that the hip joint is a ball and socket joint with a fairly large range of motion and surrounded by the biggest and strongest muscles of the body. This means that even though the joint surfaces are supposed to work in the manner we just described and experienced, the muscles can override that normal function.
Someone with excessively tight external femur rotators or pelvic flexors can have externally rotated femurs but a posteriorly tilted pelvis. The opposite can also be true where someone has excessively tight internal femur rotators or pelvic extensors can have internally rotated femurs but an anteriorly tilted pelvis. These posture imbalances create massive amounts of stress and friction in the hip joint which can lead to many hip problems including osteoarthritis over time.
Someone with excessively tight external femur rotators or pelvic flexors can have externally rotated femurs but a posteriorly tilted pelvis. The opposite can also be true where someone has excessively tight internal femur rotators or pelvic extensors can have internally rotated femurs but an anteriorly tilted pelvis. These posture imbalances create massive amounts of stress and friction in the hip joint which can lead to many hip problems including osteoarthritis over time.
 Subject 1: youth with external femurs |  Subject 1: youth with posterior pelvis |  Subject 2: elderly adult with external femurs |  Subject 2: elderly adult with posterior pelvis |
Now let's move up the body and talk about how the pelvis influences the spine and vise versa. The pelvis connects to the spine via the sacroiliac joints (SI joints) where the ilium of the pelvis connects to the sacrum of the spine. The SI joint is designed to have very limited range of motion which means any change in pelvic position should have a direct effect on the spine and vise versa.
Experiment 2: the pelvis and spine relationship
1. Sit in a chair towards the front of the seat with your feet flat on the floor and pointed straight ahead.
2. Roll your pelvis forward (anterior pelvic tilt) so you are sitting up on your sit bones. Notice what happens to your lumbar spine.
3. Roll your pelvis backwards (posterior pelvic tilt) so you are no longer sitting on your sit bones. Notice what happens to your lumbar spine.
What did you notice?
When you rolled your pelvis forward (anterior tilt) you should have noticed your lumbar spine arching (extending). When you rolled your pelvis backwards (posterior pelvic tilt) you should have noticed your lumbar spine flattening or rounding (flexing). This is the normal relationship between the pelvis and spine via the SI joints and joints of the vertebral column.
But just like what we talked about earlier that can happen at the hip joint, muscle imbalances can override normal joint function. When this happens at the SI joints, the increased stress and torque at the SI joints often creates excessive movement at the SI joint(s) that can lead SI joint dysfunction, SI joint arthritis, ankylosing spondylitis, and other problems. When the pelvis and intervertebral joints normal function is overridden by muscle imbalance and dysfunction, the results can be herniated discs, spondylosis, spondylolithesis, degenerative disc disease, scoliosis, and many other problems.
When you rolled your pelvis forward (anterior tilt) you should have noticed your lumbar spine arching (extending). When you rolled your pelvis backwards (posterior pelvic tilt) you should have noticed your lumbar spine flattening or rounding (flexing). This is the normal relationship between the pelvis and spine via the SI joints and joints of the vertebral column.
But just like what we talked about earlier that can happen at the hip joint, muscle imbalances can override normal joint function. When this happens at the SI joints, the increased stress and torque at the SI joints often creates excessive movement at the SI joint(s) that can lead SI joint dysfunction, SI joint arthritis, ankylosing spondylitis, and other problems. When the pelvis and intervertebral joints normal function is overridden by muscle imbalance and dysfunction, the results can be herniated discs, spondylosis, spondylolithesis, degenerative disc disease, scoliosis, and many other problems.
The entire spinal column is connected and works as a unit. If you flex the lumbar spine you should feel the thoracic spine start to flex also. If you extend the lumbar spine you should feel the thoracic spine start to extend also. If you rotates one part of your spine, the rest of your spine will start to rotate also. This all goes back to our basic principle that the body is a unit and everything is connected and interrelated.
Experiment 3: unilateral imbalances relationship
1. Stand up with your feet pointed straight ahead hip width apart and notice the position of your pelvis.
2. Turn your right foot out at a 45 degree angle. Notice the position of your pelvis and spine.
3. Turn your right foot in at a 45 degree angle. Notice the position of your pelvis and spine.
What did you notice?
When your feet were pointed straight ahead your pelvis and spine should have been square and even. When you turned your right foot out you should have noticed the right side of your pelvis rotated backwards and tilted posteriorly slightly and your spine rotated slightly to the right. When your turned your right foot in you should have noticed the right side of your pelvis rotated forwards and tilted anteriorly slightly and your spine rotated slightly to the left. This is what happens with left to right imbalances and is what can contribute to scoliosis.
When your feet were pointed straight ahead your pelvis and spine should have been square and even. When you turned your right foot out you should have noticed the right side of your pelvis rotated backwards and tilted posteriorly slightly and your spine rotated slightly to the right. When your turned your right foot in you should have noticed the right side of your pelvis rotated forwards and tilted anteriorly slightly and your spine rotated slightly to the left. This is what happens with left to right imbalances and is what can contribute to scoliosis.
Scoliosis
Scoliosis is caused by an imbalance left to right in the pelvis, spine, and shoulders. When one femur rotates into a different position than the other side, the pelvis tilts unilaterally, the pelvis rotates, the shoulders or scapula move into different positions, or the torso offsets or rotates, the spine will be dragged along for the ride. Improving scoliotic curve requires looking at the entire body and addressing the imbalances of the foot and lower leg, femur and pelvis, and the shoulders, scapula, and arms and not just addressing the spine.
The body is a unit and that any deviation of the femur, pelvis, or spine will affect the other components. When treating injuries and pain of the femur, pelvis, or spine we must remember to not focus on the symptom, but instead on the entire body if we want long term pain relief and optimized performance.
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