1. Posture 3

2. Ankle & Knee

3. In the optimal erect posture:
The ankle is in neutral position
The knee is in full extension
The LOG falls anterior to the midline of the knee, posterior to the patella

4. In the optimal erect posture:
This anterior position of LOG relative to the ankle joint axis creates a dorsiflexion moment So
The muscle activity of the planterflexors is necessary to prevent forward motion of the tibia

5. In the optimal erect posture:
This anterior position of LOG relative to the knee joint axis creates a extension moment So
Passive tension in the posterior joint capsule and associated ligaments prevents hyperextension

6. Hip & Pelvis

7. In the optimal erect posture:
Lines connecting the symphysis pubis and the anterior superior iliac spines are vertical
&
Lines connecting the anterior superior iliac and posterior superior iliac spines are horizontal

8. In the optimal erect posture:
LOG passes slightly posterior to the axis of the hip joint, through the greater trochanter
&
The posterior location of LOG relative to the hip joint axis creates an extension moment at the hip

9. In the optimal erect posture:
This moment tends to rotate the pelvis posteriorly on the femoral heads
&
Iliopsoas muscle works to create a balancing moment at the hip

10. Sacroiliac & Lumbosacral Joints

11. In the optimal erect posture:
The lumbosacral joint is determined by the amount of angulation that is present

12. The optimal lumbosacral angle is about 30 degrees
The lumbosacral angle is the angle formed by two lines, one drawn parallel to the ground and the other drawn in line with the superior plateau of the first sacral vertebra
The optimal lumbosacral angle is about 30 degrees

13. In the optimal erect posture:
LOG passes slightly anterior to the sacroiliac joint
The moment that is created tends to cause the superior portion of the sacrum to rotate anteriorly and inferiorly

14. In the optimal erect posture:
Since the sacral vertebrae are linked, this moment will cause the inferior portion of the sacrum in a posterior direction
Tension in the sacrospinous and sacrotuberous ligaments prevents the inferior portion of the sacrum from moving posteriorly

15. In the optimal erect posture:
The superior portion of the sacrum is kept from being pushed anteriorly by the sacroiliac ligament

16. Vertebral Column

17. In the optimal erect posture:
LOG passes posterior to the axes of rotation of the cervical and lumber vertebrae
It passes anterior to the thoracic vertebrae
It passes through the body of the fifth lumbar vertebra

18. The Head

19. In the optimal erect posture:
LOG passes through the external auditory meatus
LOG falls anterior to the transverse axis of rotation for flexion and extension of the head and creates a flexion moment

20. In the optimal erect posture:
LOG passes through the external auditory meatus
LOG falls anterior to the transverse axis of rotation for flexion and extension of the head and creates a flexion moment, which tends to tilt the head forward

21. In the optimal erect posture:
LOG passes through the external auditory meatus
It is balanced by tension in the ligamentum nuchae and tectorial membrane and the activity of neck extensors