bio mechanics of the hip
DESCRIPTION
Review anatomy of hip and its function. Analyze overall mechanical effects on hip during movement.TRANSCRIPT
Biomechanics Biomechanics of of
the Hipthe Hip
Pelvic Girdle
•The two hip bones plus the
sacrum
•Can be rotated forward,
backward, and laterally to
optimize positioning of the
hip joint
Obturator foramen
ischium
ilium
pubis
sacrum
acetabulum
Pelvic girdle
Pelvic Bone
Pelvic Bone
Anterior Tilt
• Forward tilting
and downward
movement of
the pelvis
• Occurs when
the hip extends
Posterior Tilt
• Tilting of the
pelvis
posteriorly
• Occurs when the
hip flexes
Lateral Tilt• Tilting of the pelvis from
neutral position to the right or
left
• Lateral tilt tends to occur
naturally when you support
your weight on your leg
• This allows you raise your
opposite leg enough to swing
through during gait
Pelvic Rotation• Rotation of the pelvis
defined by the direction in
which the anterior aspect
of the pelvis moves
• Occurs naturally during
unilateral leg movements
(walking)
– As the right leg swings
forward during gait the
pelvis rotates left
Hip Joint
• Consists of – Pelvic bone
•Acetabulum– Femur
Acetabulum
Acetabulum
Femur
Femur
Femur
Structure of the Hip
• A ball and socket joint in which the head of the femur articulates with the concave acetabulum
• The hip is more stable than the shoulder – Bone structure – The number and strength of the
muscles and ligaments crossing the joint
Acetabular Labrum
• Acetabulum is not a complete circle, open inferiorly
• This opening is closed by the transverse ligament
Head Ligament
• Head of femur attached to inside of acetabulum by ligamentum teres
Capsule
Ligaments
• Iliofemoral ligament or the “Y ligament of Bigelo”– Triangular in shape– Supports hip anteriorly, resists extension,
internal rotation and some external rotation
• Pubofemoral– Runs from the superior pubic ramus and the
acetabular rim, to just above lesser trochanter
– Resists abduction with some resistance to external rotation
Ligaments
• Ischiofemoral ligament– From the ischium to the posterior neck
of the femur – is directed upwards and laterally
– Resists adduction and internal rotation– All three loose during flexion
Ligaments
Anterior view
Posterior view
Vascular
Vascular
Lumbar Division
Hip Goniometry
• Flexion/Extension– 125-140 (with knees flexed)/0/10-
20– 90 (with knees extended)/0/10-20
• Abduction/Adduction– 45/0/20-30
• Internal Rotation/External Rotation– 35-45/0/40-50
Hip Movements
• Hip Flexion
• Flexion– Psoas major– Iliacus
– Assisted by:•Pectineus
•Rectus femoris
•Sartorius
•Tensor fascia latae
Hip Movements
Psoas major
Iliacus
Pectineus
Rectus femoris
Sartorious
Tensor fascia latae
Iliotibial band
• Hip Extension
Hip Movements
• Extension
– Gluteus Maximus– Hamstrings
•Biceps Femoris
•Semimembranosus
•Semitendinosus
Hip Movements
Gluteus maximus
• Hip Abduction
Hip Movements
• Abduction
– Gluteus Medius
– Assisted By:• Gulteus Minimus
Hip Movements
Gluteus medius
Gluteus minimus
• Hip Adduction
Hip Movements
• Adduction
– Adductor Magnus
– Adductor Longus
– Adductor Brevis
– Assisted By:•Gracilis
Hip Movements
Gracilis
• Internal/Medial
Rotation
– Gulteus
Minimus
– Tensor fascia
latae
Hip Movements
• External/Lateral
Rotation
– Obturator Externus
– Obturator Internus
– Quadratus femoris
– Piriformis
Hip Movements
Obturator Externus
Obturator Internus
Piriformis
Quadratus femoris
Angle of Inclination
Coxa Vara• The angle of inclination is less than
125 degrees • This shortens the limb• Increases the effectiveness of the
abductors• Reduces the load on the femoral
head • Increases the load on the femoral
neck
Coxa Valga
• The angle of inclination is greater than
125 degrees
• This lengthens the limb
• Reduces the effectiveness of the
abductors
• Increases the load on the femoral head
• Reduces the load on the femoral neck
Hip Angles
• 14-15 degrees
• Moves CM more
directly over
base of support
Anteversion• The angle of the
femoral neck in the
transverse plane
• Normally the femoral
neck is rotated
anteriorly 12 to 14
degrees with respect
to the femur
Excessive Anteversion• Excessive anteversion
beyond 14 degrees causes the head of the femur become uncovered
• In order to keep the head of the femur within the acetabulum a person must internally rotate the femur
Retroversion
• The angle of anteversion
is reversed so that it
moves posteriorly
• This condition causes
the person to externally
rotate the femur
Loads on the Hip• During swing phase of walking:
– Compression on hip approx. same as body weight (due to muscle tension)
• Increases with hard-soled shoes• Increases with gait increases (both
support and swing phase)• Body weight, impact forces
translated upward thru skeleton from feet and muscle tension contribute to compressive load on hip
600 N
250 N
Using A Walking Stick
Using a walking stick how it reduces JRF
• In equilibrium sum of moments = 0
• Without stick
M x A = W x B
M = (W x B)/A
Using a walking stick how it reduces JRF
Using a walking stick how it reduces JRF
• With sitck(M x A)+(Ws x C) = W x BM = [(W x B)-(Ws x C)]/A
• So the force required by the abductors M is smaller if a stick is used
• The bigger C is, the smaller M is therefore a walking stick in the hand furthest away from the hip is most effective
Using a walking stick how it reduces JRF
• In equilibrium, the sum of the forces in the Y plane = 0
• Without stick
JRF sin = M + W
• With stick
JRF sin + Ws = M +W
JRF sin = M + W - Ws
Using a walking stick how it reduces JRF
• Therefore JRF is less when a
walking stick is used. Not only is M
force smaller, but the upward force
exerted by the stick reduces the
JRF further
Using a walking stick how it reduces JRF
W
opposite
hurtleg
W
same
hurtleg