Kinesiology Hip Bone and Support Structures

Bones of hip joint

Pelvis (Ilium, ischium, pubis), Femur

Articular Surfaces of hip joint

Acetabulum, femoral head

Ligaments of hip joint

Iliofemoral, pubofemoral, ischiofemoral, joint capsule, ligamentum teres

Stabilizing factors of hip joint

Shape of articular surfaces, fibrocartilage, muscle

Hip functional role

Stability and mobility (absorbs and transmits enormous forces while allowing a large arc of motion)

Characteristics of shaft of the femur

-Slightly convex

-Bows when body weight is placed

-Bone experiences compression posteriorly and tension anteriorly

-Allows for greater weight bearing capacity

Mechanical axis

Connects center of hip joint to center of knee joint

Anatomical axis

runs along shaft of femur

Anatomical axis is ___ to mechanical axis

lateral

Angle of inclination

Angle in frontal plane between femoral neck and medial side of femoral shaft

What degree is angle of inclination at birth?

165-170 degrees

Normal angle of inclination

~125 degrees

What happens when angle of inclination is abnormal?

Affects the articular fit and potentially lead to excessive degeneration of joint

Coxa vara angle of inclination

less than 125 degrees

Coxa valga angle of inclination

greater than 125 degrees

Coxa vara increases or decreases shear forces?

Increases shear forces

Coxa vara lengthens or shortens hip abductor moment arms

lengthens moment arm

Coxa vara reduces

joint reaction forces

Does coxa vara improve stability?

yes, coxa vara improves stability

Joint reaction force

-amount of compressive force through 2 joint forces

-forces generated within a joint in response to internal and external forces

-represent net force transmitted across articular surfaces of a joint

Which is more stressful to hip joint coxa vara or coxa valga?

coxa valga

Coxa valga presisposes to ______

hip dislocation

Coxa valga increases or decreases shear forces?

decreases

Coxa valga increases or decreases hip abductor moment arm

decreases moment arm

Coxa vara and coxa valga have increased or decreased chance of genu valgum?

increased

Does coxa valga increase or decrease stability?

decrease

does coxa valga increase or decrease joint reaction forces?

decrease joint reaction forces

Femoral torsion

Describes relative rotation (twist) of shaft between axis of knee and femoral neck

Normal anteversion of femoral torsion

~15 degrees anterior to a medial lateral axis through femoral condyles

Femoral torsion happens in what plane?

transverse plane

Femoral anteversion the hip is less or more stable?

less stable

Excessive anteversion with “in-toeing”

-pigeon toed

-internally rotated alot

-external rotation is limited

Retroversion

-excess external rotation

-less internal rotation

Stability

-joint surfaces

-acetabulum with labrum

-bony trabeculae

-large muscle mass

Mobility

-Large surface area of joint

-No barriers to motion from adjacent joints

-Capsular redundancy

Shortening of soft tissues can lead to reduction in

ER ROM

Hip joint Flexion/extension degrees

120/20°

hip joint Abduction/adduction degrees 

40/25°

hip joint Internal/external rotation

35/45°

Pubic symphysis provides stress relief through the ring of pelvis during ____

walking

how would force travel through the proximal femur with a normal vs with a coxa vara deformity?

More Shear force

Higher internal forces mean

higher joint reaction forces

infants are born with how many degrees of anteversion?

~40 degrees that de-rotates to the normal 15 degrees by around 16 years of age

Ligamentum Teres is stretched with a combination of

flexion, adduction, and external rotation

Ligamentum Teres

Helps provide stability within the hip joint, particularly in cases of hip dysplasia when the acetabular socket fails to adequately contain the femoral head

Ligamentum teres runs between

transverse acetabular ligament and fovea

Acetabular Labrum

-Adds stability to femoral head by deepening socket by ~30% → suction force

-Dissipates load by increasing acetabular surface area 

“Suction seal”

Mechanical seal formed around the hip by an intact labrum helps maintain negative intraarticular pressure, which is effective at resisting separation of the joint surfaces

Acetabular Labrum

Poorly vascularized, but well innervated

Center-edge angle: normal range and significance?

Measures superior femoral head coverage

• Normal: 25–40°

• 40°: Pincer impingement

• <20°: Dysplasia

• Decreased angle → ↓ coverage, ↑ joint pressure

Acetabular anteversion angle: normal range and significance?

Measures anterior femoral head coverage.

• Normal: 15–20°

• Increased angle → ↑ anterior exposure, ↑ labral tears and anterior dislocation

Normal femoral anteversion angle?

Approximately 15°

Joint Capsule

• Large and strong

• Much of femoral neck covered

• Small inferior redundancy

Ligaments

• Strongly reinforce capsule

• “Twisted" taut in extension

• Loose in flexion

Iliofemoral “Y ligament” prevents excessive

Extension and External Rotation

Pubofemoral restricts prevents excessive

Abduction, Extension, ER

schiofemoral restricts prevent excessive

IR, Extension

Hip loose-packed position?

30° flexion, 30° abduction, slight ER

Hip close-packed position?

Full extension (~20°), slight abduction, slight IR

Hip joint most congruent position?

90° flexion, moderate abduction and ER

Hip capsular pattern?

IR > flexion > abduction = extension

What does the hip capsular pattern indicate?

Motion loss due to capsular pathology

What is the purpose of the hip close-packed position?

Maximizes ligament tension/elongation

People with Paraplegia

• May be able to ambulate by hanging on their “Y ligaments” and using a knee-ankle-foot orthosis (KAFO).

• This is achieved by placing their body’s center of mass posterior to their hip joint.

Femur on pelvis flexion

anterior roll and posterior slide 

femur on pelvis extension

posterior roll and anterior slide

Femur on pelvis Abduction

superior roll and inferior slide

femur on pelvis adduction

inferior roll and superior slide

femur on pelvis external rotation

posterior roll and anterior slide

femur on pelvis internal rotation

anterior roll and posterior slide

pelvis on femur anterior pelvic tilt

anterior roll and slide

pelvis on femur Posterior pelvic tilt

posterior roll and slide

pelvis on femur abduction

superior roll and slide

pelvis on femur adduction

inferior roll and slide

pelvis on femur internal rotation

anterior roll and slide

pelvis on femur external rotation

posterior roll and slide

Cantilever Bending

-Superior aspect of femoral neck experiences tensile stress

-Inferior aspect experiences compressive stress

Clinical application

• Stress fractures of the femoral neck can occur in the superior and inferior aspects

• Treatment for superior neck fractures may include surgery

• Treatment for inferior neck fractures may only include rest (non or limited weight bearing) followed by gradual return to normal weight bearing activities.