Hip Biomechanics Part 2

Question 1

Hip Flexors: Sagittal Plane

Answer 1

Iliopsoas
Sartorius
Rectus femoris
Tensor fasciae latae
Adductor longus
Pectineus

Question 2

Hip Extensor Muscles

Answer 2

Gluteus maximus
Hamstrings (Except biceps femoris short head)
Adductor magnus (posterior head)

Controls forward lean

Question 3

Hip Adductor Muscles: Frontal

Answer 3

Pectineus
Adductor longus
Gracilis
Adductor brevis
Adductor magnus

Regardless of hip position, posterior head of adductor magnus is a hip extensor

Most other adductor muscles are considered flexors from the anatomic (extended) position

Beyond 40°–70° of hip flexion, the adductor muscles become extensors

Question 4

Hip Abductor Muscles : Frontal

Answer 4

Gluteus medius
Gluteus minimus
Tensor fasciae latae

Hip abductors produce hip abduction
moment to stabilize pelvis over
relatively fixed femur (preventing hip drop)

Glute medius contributes the most Hip contact force during single limb support (may also show trendelenburg)

Question 5

Hip Abduction JRF, Torque and Joint angle

Answer 5

Reduce JRF by leaning toward the support limb; moment arm for body weight will decrease

Hip abductors produce their peak torque when elongated; needed to provide frontal plane
stability during walking (single limb support)

Question 6

Hip External Rotator: Horizontal/Transverse Plane

Answer 6

Gluteus maximus
Piriformis
Obturator internus
Gemellus inferior
Gemellus superior
Quadratus femoris

Contraction of the external rotators on the right rotates the pelvis and trunk to the left ; Functionally, this is used to abruptly change direction while running

With more hip flexion, some external rotators become internal rotators

Question 7

Hip Internal Rotators: Transverse Plane

Answer 7

No Primary.

Secondary:
Gluteus minimus (anterior fibers)
Gluteus medius (anterior fibers)
Tensor fascia latae
Adductor longus
Adductor brevis
Pectineus

With more hip flexion, the internal rotation potential of the internal rotators dramatically increases.

Internal rotators rotate the pelvis in the horizontal plane over relatively fixed femur

Question 8

Maximal Torque

Answer 8

Extensors -> Flexors -> Adductors -> Abductors -> Internal Rotators -> External Rotators