Biomechanics and movement considerations of the hip joint

What is coax vara?

The angle of inclination of the femoral head in the acetabular joint is lower than normal.

X<125

What does the Iliofemoral ligament resist?

Hip extension and external rotation

What is the hip's resting position?

30 degrees of flexion, 30 degrees of abduction, and slight lateral rotation.

What are the primary muscles for hip flexion?

Iliopsoas

Sartorius

TFL

Rectus femoris

Pectineus

What are the secondary hip extensors?

Middle and posterior fibers of the gluteus medius

Anterior fibers of the adductor magnus

When can the adductor magnus aid in hip extension?

When the hip is flexed to around 70 degrees and more.

What are the secondary hip adductors?

Biceps femoris (long head)

Gluteus Maximus inferior

Quadratus femoris

Obturator externus

When do the hip abductor muscles produce the most torque?

With a lower hip angle

What are the secondary hip internal rotators?

Anterior fibers of the gluteus medius and gluteus minimus

Tensor fascia latae

Adductor longus

Adductor brevis

Pectineus

Semitendinosus

Semimembranosus

What helps increase the internal torque potential of the internal rotators?

Flexing the hip to 90 degrees.

What are the secondary hip external rotators?

Posterior fibers of the gluteus medius and minimus

Obturator externus

Sartorius

Long head of the biceps femoris

What do the right and left innominate bones connect posteriorly?

Sacroiliac (SI) joints

What is the normal angle of inclination in the acetabular joint?

125

What is the femoral torsion angle for an adult?

15 degrees, but can vary from 8-20

What is the hip joint designed for?

Stability

Load transmission

Multiplanar movement

What is the hip's integrated system to withstand high forces consist of?

Articular cartilage

Compact and cancellous bone

Surrounding muscles, tendons, and ligaments

What is the acetabulum?

A deep hemispheric cup like socket that articulates with the femoral head.

What is the acetabular notch?

An inferior opening bridged by the transverse acetabular ligament.

What does the acetabulum do in the stance phase?

The lunate surface slightly deforms, the transverse acetabular ligament elongates, and the acetabular notch widens.

This results in increased contract area with reduced peak contract stress.

What is the acetabular fossa?

Central depression located deep with the acetabulum.

What is the acetabular labrum?

A strong yet flexible ring of fibrocartilage surrounding the acetabular rim.

What are the acetabular labrum's functions?

Deepen the socket of the acetabulum.

Enhance joint congruency and load distribution

What would a labral injury do to the hip?

Disrupt joint stability and mechanics, reduce the effectiveness of the fluid seal, and to pain and functional limitations.

What movements does the pubofemoral ligament resist?

Hip abduction

Hip extension

Hip external rotation

What movements do the Ischiofemoral ligament resist?

Internal rotation

Stability in extension

What is the hip's close packed position?

Full extension (roughly 20 degrees), slight internal rotation, and slight abduction

What is the capsular pattern of the hip?

Flexion, abduction, and internal rotation

What is the position of greatest hip congruency in the hip?

90 degrees of flexion

Moderate abduction

External rotation

What is a Pavlik harness?

A harness used for developmental dysplasia of the hip that keeps the hip at 90 degrees

What are the osteokinematics for femur on pelvic movement?

Flexion

Extension

Abduction

External rotation

Internal rotation

What are the American Academy of Orthopaedic Surgeons (AAOS) normative values?

Flexion: 120 degrees

Extension: 20 degrees

Abduction: 40 degrees

Adduction: 25 degrees

External rotation: 45 degrees

Internal rotation: 45 degrees

Where does the lumbar plexus receive its neural input from?

Ventral rami levels T12-S4

What are the secondary muscles for hip flexion?

Adductor brevis

Gracilis

Anterior fibers of the gluteus medius

What leads to anterior pelvic tilt?

Force couple formed between the hip flexors and low back extensor muscles.

What does anterior pelvic tilt result in?

Increased lumbar lordosis

What optimizes the alignment of the entire spine?

Lumbopelvic posture with a normal or typical amount of lumbar lordosis.

How do the abdominals stabilize the pelvis?

By promoting a posterior pelvic tilt.

What are the primary hip extensors?

Gluteus Maximus

Hamstrings

Posterior head of the adductor Magnus

What are the primary hip adductors?

Pectineus

Adductor longus

Gracilis

Adductor brevis

Adductor magnus

What are the secondary hip abductors?

Piriformis

Sartorius

Rectus femoris

Gluteus maximus

What is the primary function of the hip abductors?

To provide frontal plane stability to the pelvis's while in the stance phase of gait.

What are the primary hip external rotators?

Gluteus maximus

Piriformis

Obturator internus

Superior and inferior gemellus

Quadratus femoris

What dominates the kiniesologic role in movements of the lower extremity, trunk, and whole body?

Hip joint

What does an injury affecting the hips cause functional limitations to?

Difficulty walking

Dressing

Driving a car

Lifting and carrying loads

Climbing stairs

What are the three bones that form the hip?

Ilium

Pubis

Ischium

How do the right and left innominate bones connect anteriorly?

Pubic symphysis

What do the SI joints and pubic symphysis forming a continuous osteoligametous ring make?

The pelvis

What are the pelvis 3 main functions?

1. Common attachment point for muscles of the lower extremity and trunk.

2. Transmits weight of the upper body and trunk.

3. With aid of muscles and connective tissue of the pelvic floor it supports the organs involved with bowel, bladder, sexual, and reproductive functions.

What are the 3 distinct features of the external surface of the pelvis?

1. Large fan-shaped wing of the ilium forming the superior half of the innominate.

2. Deep cup shaped acetabulum

3. The obturator foramen- the largest foramen in the body. Covered by an obturator membrane.

What is the head of the femur?

Projects medially and slightly anteriorly to articulate with the acetabulum

What is the femoral neck?

Connects the femoral head to the shaft.

Serves to displace the proximal shaft of the femur laterally away from the joint, facilitating clearance required between the femur and pelvis during locomotion.

What is the shaft of the femur?

Projects slightly medially, placing the knees and feet closer to the midline of the body.

What is coxa valga?

angle of inclination greater than 125 degrees

X>125

What is femoral torsion?

Describes the relative rotation (twist) between the femur's shaft and neck.

What is a healthy infants femoral torsion angle?

40 degrees of femoral anteversion

When does femoral torsion usually de-rotate?

Around 16 years of age with continued bone growth, increased weight bearing across the joint and muscle activity.

What is anterversion also known as?

In-toeing

What is compact bone?

Dense, strong outer layer of bones.

Found primarily in the shaft of long bones.

What is cancellous (trabecular) bone?

Porous, sponge-like structure

Energy absorbing

Found primarily at the ends of long bones (epiphysis)

What is the only part of the femoral head that isn't covered with articular cartilage?

Fovea

What contributes to blood supply in infants for the femoral head?

The ligamentum teres contributes to blood supply via the acetabular artery

What contributes to blood supply for the femoral head in adults?

Medial circumflex artery

Lateral circumflex artery

What is the ligamentum teres?

ligament of the head of the femur

May assist in joint stability, particularly in hip flexion, adduction, external rotation, and deep hip flexion

What does the acetabular fossa lack?

Lacks articular cartilage (does not contact the femoral head)

What forces act on the acetabulum labrum?

Compressive and tensile

What are the three primary ligaments of the hip?

Iliofemoral ligament

Pubofemoral ligament

Ischiofemoral ligament

What is the Iliofemoral ligament?

Strongest and stiffest ligament of the hip

What is the pubofemoral ligament?

Blends with the joint capsule anteriorly

What is the Ischiofemoral ligament?

Spirals around the posterior aspect of the hip

Where is the axis of rotation for the femur's movement with the pelvis?

Near the center of the femoral head

What is ipsi-directional lumbopelvic rhythm?

Same direction

What is contra-directional lumbopelvic rhythm?

Opposite

Used in walking

What innervates most muscles involved in hip flexion and knee extension?

Femoral nerve (L2-L4)

What innervates the muscles of hip adduction?

Obturator nerve (L2-L4)

What innervates the posterior hip structures?

The sacral plexus (L4-S4) and exits the pelvis via the greater sciatic foramen

What is Hilton's law?

Nerves that supply muscles acting on a joint also supply:

The joint itself

The skin overlying the muscles

What does hip flexion require?

Coordinated activation of hip flexors and abdominal musculature.

What is the clinical implication of weak abdominals?

Inadequate posterior pelvic control

Results in:

Increased anterior pelvic tilt

Increased lumbar lordosis

What work as a force-couple to posteriorly tilt the pelvis?

The hip extensors and abdominal muscles

What are the primary hip abductors?

Gluteus medius

Gluteus minimus

Tensor fascia latae

What kind of levers are the hip abductors in the hip?

1st class levers

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