Joint Biomechanics - Hip Flashcards
Hip Joint
Diarthroses: powerful weight bearing ball and socket joint between acetabulum(concave) and femoral head (convex).
Flexion/extension - Sagittal plane, transversal axis.
Abduction/adduction - Frontal plane, antero-posterior axis.
Internal/external rotation - Transverse plane, longitudinal axis.
Good functionality in endurance and explosive movements.
Acetabulum - Lunate Surface
Lunate surface of the acetabulum is covered with hyaline cartilage and articulates with the head.
Inferior margin of lunate is interrupted by acetabular notch, spanned by the transverse acetabular ligament that connects the two ends.
Acetabulum - Labrum
Edge of the acetabulum.
Prevents bone to bone contact.
Increases surface area.
Protects femoral head in extreme movement.
Center Edge Angle/Angle of Wiberg
Represents the amount of inferior tilt of the acetabulum. Measures the amount of coverage over the femoral head.
Using a line connecting the lateral rim of the acetabulum and the center of the femoral head, and the vertical line through the center of the femoral head.
Around 38° in men.
Around 35° in women.
What is the orientation of the acetabulum on the hip bone?
Inferiorly, laterally and anteriorly
Angle of Acetabular Anteversion
Magnitude of anterior orientation of the acetabulum on the hip bone.
Around 18,5° in men.
Around 21,5° in women.
Head of Femur
2/3 of a sphere, flat on the top. Stability is increased by it.
Fovea not covered with articular cartilage, where ligament of the head of the femur (ligamentum teres) is attached.
Femoral head attached to it, angulated so that the head faces medially, superiorly and anteriorly.
Degree of Center Edge Angle
18° - Developmental dysplasia of the hip
24° - Borderline
33° - Normal
48° - Femoro-acetabular impingement (bone to bone)
Angle of Inclination (neck to shaft angle)
2 angulations made by the head and the neck in relation to the shaft.
Occurs in the frontal plane.
Ranging from 115° to 140° in normal adults.
Greater in infancy and declines in elderly.
Coxa Vara
Pathologic decrease in the angle of inclination of the femur. Significantly less than 115°.
Coxa Valga
Pathologic increase in the angle of inclination of the femur. More than 140°.
Angle of Torsion
Can be viewed by looking down the length of the femur.
One axis is through the femoral head and neck and the other axis is through the femoral condyles.
Average angle 15°-20° in adults without impairments.
Axis of the head and neck is positioned anteriorly compared to the axis of condyles.
Antiversion
Pathologic increase in the angle of torsion (more than 20°).
Easy internal rotation, difficult external rotation.
Retroversion
Pathologic decrease in the angle of torsion (less than 15°).
Easy external rotation, difficult internal rotation.
Normal Hip Range of Motion
Flexion: 140° Extension: 15° Abduction: 40-50° Adduction: 20-30° External Rotation: 45-50° Internal Rotation: 35-40°
Hip Flexion Range of Motion
With a flexed knee, without help: 120°
With a flexed knee, passively (with help): 145°
With a extended knee: 90° (because of hamstring tension)
Extracapsular Ligaments - Iliofemoral Ligament
Y-shaped with two parts: superior, inferior. Strongest of the three ligaments. Origin: AIIS, acetabular limbus Insertion: Intertrochanteric line Anterior-superior.
Extracapsular Ligaments - Ischiofemoral Ligament
Origin: Ischium
Insertion: Greater trochanter
Posterior.