- The hip joint, also known as the femoroacetabular joint, is a synovial triaxial (polyaxial) joint.
- It is formed by the head of the femur meeting the acetabulum of the pelvic bone.
- It allows motion in all three cardinal planes:
- flexion/extension in the sagittal plane.
- anterior tilt / posterior tilt of the pelvis in the sagittal plane.
- abduction/adduction in the frontal (coronal) plane.
- depression/elevation of the pelvis in the frontal plane
- lateral rotation/medial rotation (external/internal rotation) in the transverse (horizontal) plane.
- contralateral rotation / ipsilateral rotation of the pelvis in the transverse plane.
- flexion/extension in the sagittal plane.
NOTES:
- When the femur moves at the hip joint, there is a coupled action of movement of the pelvis (at the sacroiliac and lumbosacral joints). This coupling of joint actions is called femoropelvic rhythm.
- With femoropelvic rhythm, when the pelvis moves, there will be compensatory movement of the spine.
- The reverse closed-chain joint actions of the pelvis at the hip joint are likely just as important as the standard open-chain joint actions of the thigh/femur at the hip joint.