ESS 303 – Biomechanics

Hip Joint

♀/♂ Differences (Women)

Entire pelvic girdle tilted forwardBones thinner and lighterGreater distance between greater-

superior iliac spines (wider greater or false pelvis)

Wider and more spherical true pelvisMore triangular obturator foramenShallower symphasis pubisWider & more rounded pubic angle

Sacral Positions

NeutralSacral Flexion(With Trunk Extension)

Sacral Extension(With Trunk Flexion)

6 Pelvic Positions

Anterior tilt (with trunk flexion or thigh extension)

Posterior tilt (with trunk extension or thigh flexion)

Left lateral tilt (left side drops)

Right lateral tilt (right side drops)

Left rotation (left back/right forward)

Right rotation (right back/left forward)

4 Femur Neck Angles

1. Angle of inclination=125º is normal>125º is coxa valga<125º is coxa vara

2. Angle of torsion12 to 14º is normalHead forward is anteversion or internal femoral

torsion (toeing in) – common & usually outgrown in children

Head back is retroversion (toeing out)

4 Femur Neck Angles

3. Angle of Wiberg

Increases with age

Male: about 38°

Female: about 35°

4. Acetabular anteversion

Male: about 18.5°

Female: about 21°

Some Final Notes

Roundness of acetabulum decreases with age

Transmision of forces between upper and lower extremities

Acetabular labrum (fibro-cartilage lip)Adds stabilityDeepens socketIncreases concavityGrasps head

Movements and Major Muscles

Adduction: Gracilis & adductors (longus, brevis & magnus) Abduction: Gluteus medius & gluteus minimus Flexion: Iliopsoas (iliacus & psoas major) & rectus femoris Extension: Gluteus maximus & hamstrings

(semitendinosus, semimembranosus & biceps femoris) Internal (medial) rotation: Gluteus medius, gluteus

minimus External (lateral) rotation: Gluteus maximus, adductor

brevis & aductor magnus Circumduction, horizontal (transverse) abduction,

horizontal (transverse) adduction, hyperabduction, hyperadduction & Hyperextension : Combinations or exaggerations of above