Lesson
Hip Joint
NOTES:
1.Pelvis’ main role of stability has been achieved with loss of mobility at sacroiliac joint and symphisis pubis. Acetabulum faces laterally, antriorly and inferiorly. Femur head faces medially, anteriorly and superiorly
2.Movements of the femur are primarily due to rotations at HIP JOINT.
3.However, PELVIC GIRDLE positions the hip joint for effective lower limb movement
4.Although the pelvis is a single non-jointed structure, it can rotate in all 3 planes of motion
5.The pelvis facilitates movement of the femur by rotating so that the acetabulum is placed in a direction which facilitates impending femoral motion
6.Eg. posterior pelvic tilt + Anterior Superior Iliac Spine (ASIS) tilted back with respect to acetabulum puts head of femur in front of hip boneto enable flexion. Anterior pelvic tilt promotes femoral extension and lateral pelvic tilt to opposite side facilitates lateral movement of femur.
7.Pelvic girdle movements also coordinate with some movements of the spine
8.Outward (external) rotation of femur occurs with every step of gait (which is otherwise mainly a sagittal plane movement), to accommodate the rotation of the pelvis. Medial rotation of the femur is typically not a resisted motion and does not require a lot of muscular force. The medial rotators have only 1/3rd the strength of the lateral rotator
9.Horizontal abduction can take place when the hip flexors are in tension to raise the femur. Then the abductors can act. Posterior muscles of the hip are more effective than anterior ones as they are already stretched when the hip is in 90º of flexion, whereas the anterior ones have reduced tension in this position (tension = activation)