Hip Bone and Support Structures

Mechanical axis of femur

connects center of hip joint to center of knee joint

Anatomical axis of femur

runs along the shaft of the femur

The mechanical axis of femur represents _______ when weight-bearing

line of force

angle of inclination

The angle between the shaft and the neck of the femur in the frontal plane

optimal angle of inclination to properly align the joint surfaces

125º

Angle of inclination at birth

165 - 170º

coxa vara angle of inclination

less than 125 degrees

coxa valga angle of inclination

greater than 125 degrees

Coxa-vara deformity increases...

naturally occurring bending forces which increase shear across femoral neck

coxa-vara deformity lengthens....

hip abductor moment arms

Joint Reaction Force (JRF)

force generated within a joint in response to internal and external forces acting on the joint

Higher internal force =

higher joint reaction force

Coxa-valga deformity may predispose

hip dislocation or degenerative joint disease as JFRs are significant

Coxa-valga deformity decrease

shear forces across femoral neck

Coxa-valga deformity increase

functional hip abduction muscle length and reduced moment arm

femoral torsion

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

normal anteversion

15 degrees anterior to frontal plane through femoral condyles

Excessive anteversion with "in-toeing"

abnormal gait pattern with exaggerated posturing of lower limb internal rotation

excessive anteversion

more than 15 degrees anterior to frontal plane through femoral condyles

retroversion of femoral torsion

less than 15 degrees anterior to frontal plane through femoral condyles

Retroversion of hip

limited hip IR and excessive ER; generally "toeing out".

Stability of hip joint related to....

- joint surfaces

- acetabulum with labrum

- bony trabeculae

- large muscle mass

mobility of hip joint related to....

- large surface area of hip

- no barriers to motion from adjacent joints

- capsular redundancy

ligamentum teres believed to be stretched with a combination of...

flexion, abduction, and external rotation

acetabular labrum function

adds stability to femoral head by deepening socket by 30º through suction force

Labral contact area percentage in swing phase

20%

Labral contact area percentage in midstance phase

98%

What is the normal osteokinematic range of motion for hip flexion?

120°

What is the normal osteokinematic range of motion for hip extension?

20°

What is the normal osteokinematic range of motion for hip abduction?

40°

What is the normal osteokinematic range of motion for hip adduction?

25°

What is the normal osteokinematic range of motion for hip internal rotation?

35°

What is the normal osteokinematic range of motion for hip external rotation?

45°

How many degrees of freedom does the hip joint possess?

Three degrees of freedom (rotates in sagittal, frontal, and horizontal planes).

What primary function of the hip joint?

The balance between providing stability (absorbing and transmitting large forces) and mobility (allowing a large arc of motion).

Which three bones fuse together to form the innominate bone?

Ilium, ischium, and pubis.

What anatomical feature of the femoral shaft enhances its weight-bearing capacity?

Slight anterior convexity (anterior bowing).

Under weight-bearing conditions, what type of mechanical stress is experienced on the posterior aspect of the femoral shaft?

Compressive stress

Under weight-bearing conditions, what type of mechanical stress is experienced on the anterior aspect of the femoral shaft?

Tensile stress

What arteries provide the primary blood supply to the head and neck of the femur?

Medial and lateral circumflex arteries.

What is the primary functional role of the ligamentum teres?

It acts as a protective sheath for the acetabular artery supplying blood to the femoral head.

How does the internally rotated posture of in-toeing compensate for excessive femoral anteversion during walking?

It guides the femoral head more directly into the acetabulum and increases the moment arm of the hip abductor muscles.

How does the acetabular labrum assist in joint force dissipation across the hip?

It increases the acetabular surface area, spreading force across a larger contact region.

What is the term for the fluid-tight seal created around the hip joint by an intact labrum?

Suction seal

What two key mechanical functions are provided by the acetabular labrum's suction seal?

- Maintains negative intra-articular pressure to resist joint surface separation.

- Seals in synovial fluid to decrease friction over weight-bearing surfaces."

What are the vascularity and innervation properties of the acetabular labrum?

It is poorly vascularized, but well innervated.

center-edge angle

The degree to which the acetabulum covers the femoral head; normal is 25-40º

Pincer deformity

Acetabular overcoverage of the femoral head causing it to be too deep, >40º center-edge angle

Dysplasia of the hip

acetabulum forms incompletely or ligaments of hip joint are loose so head of femur slips out of joint,

acetabular anteversion angle

measures the fixed orientation of the acetabulum within the horizontal/transverse plane, relative to the pelvis

degree that acetabulum overhangs front of femoral head; 15-20º

Which hip capsular ligament is considered the strongest and stiffest in the body?

Iliofemoral ligament

What distinctive shape does the iliofemoral ligament resemble?

An inverted "Y"

Which primary sagittal plane hip movement twists and tautens the hip ligaments?

Hip extension

The Iliofemoral ligament prevents excessive

extension and external rotation

pubofemoral ligament prevents excessive

abduction, extension, ER

ischiofemoral ligament prevents excessive

internal rotation and extension

Hip capsular ligaments are taut with which movements?

Extension, abduction, and internal rotation.

What is the Close-Packed Position (CPP) of the hip joint?

Full extension (up to ~20°), slight abduction, and slight internal rotation.

What is a primary clinical application of placing the hip in its Close-Packed Position?

To stretch and elongate the capsular ligaments.

What is the Loose-Packed Position (LPP) of the hip joint?

30° flexion, 30° abduction, and slight external rotation.

In what position are the articular surfaces of the hip joint most congruent?

About 90° flexion, moderate abduction, and moderate external rotation.

What is the characteristic capsular pattern of motion loss for the hip joint?

Internal rotation > flexion > abduction = extension.

Structural classification of the hip joint is a synovial _____ joint.

Ball-and-socket (spheroidal)

During open-chain femoral-on-pelvic flexion, what roll and slide directions occur at the femoral head?

Anterior roll and posterior slide

During open-chain femoral-on-pelvic extension, what roll and slide directions occur at the femoral head?

Posterior roll and anterior slide.

During open-chain hip abduction, in what direction does the femoral head slide relative to its roll?

Superior roll and inferior slide

During open-chain hip adduction, in what direction does the femoral head slide relative to its roll?

Inferior roll and superior slide

During open-chain hip internal rotation, in what directions do the roll and slide of the femoral head occur?

Anterior roll and posterior slide.

During open-chain hip external rotation, in what directions do the roll and slide of the femoral head occur?

Posterior roll and anterior slide.

During closed-chain anterior pelvic tilt, in what directions do the roll and slide of the pelvis occur?

anterior roll and anterior slide

During closed-chain posterior pelvic tilt, in what directions do the roll and slide of the pelvis occur?

posterior roll and posterior slide

During closed-chain hip abduction, in what directions do the roll and slide of the pelvis occur (of hip making contact with ground)?

superior roll and superior slide

During closed-chain hip adduction, in what directions do the roll and slide of the pelvis occur (of hip making contact with ground)?

inferior roll and inferior slide

During closed-chain hip internal rotation, in what directions do the roll and slide of the pelvis occur?

anterior roll and anterior slide

During closed-chain hip external rotation, in what directions do the roll and slide of the pelvis occur?

posterior roll and posterior slide

Cantilever bending

Bending caused by superior aspect of femoral neck experiencing tensile stress while inferior aspect experiences compressive stress

Stress fractures of the femoral neck can occur in the.....

superior and inferior aspects

superior stress fractures get ...... when weight is put on it

pulled apart

inferior stress fractures get ...... when weight is put on it

pushed together

treatment for superior neck fractures may include

surgery

treatment for inferior neck fractures may include

rest followed by gradual return to normal weight bearing activities