HIP JOINT

HIP JOINT
⚫ Hip joint is a di-arthrodial joints of ball and socket type between
the femur & hip bone. It is the junction between trunk & lower
limb.
⚫ The dome-shaped head of the femur forms the ball, which fits
snuggly into the concave socket of the acetabulum.
⚫ The hip joint is composed of the pelvic acetabulum, the head of the
femur, and the femoral neck, and is controlled and protected by
the acetabular labrum, the joint capsule, and many powerful
muscles, when these fundamental structures work in tandem, the
 Osteology of hip bone

⚫ Each innominate consists Union

of 3 bones:-
Ilium
Pubis
Ischium
⚫ The right and left innominates
connect with each other anteriorly
at the pubic symphysis and
posteriorly at the sacrum.
❑ Acetabulam.
⚫ The external surface of
innominate has 3 conspicuous
features-
Large fan-shaped wing (or ala) of
the ilium forms the sup. ½ of the
innominate.
just below, deep cup shaped
acetabulam.
Just inf. & slightly med. to
acetabulam is the large obturator
foramen, covered by obturator
membrane.
 THE ACETABULUM:
⚫ Acetabulum: the ilium and ischium
contribute about 75%, and the pubis
contributes approximately 25%.
⚫ The acetabulum is the concave portion
of the ball and-socket hip joint structure.
The acetabulum is not completely
spherical due to the acetabular notch in
its inferior region, which makes it
fundamentally horseshoe shape.
⚫ Articulation in the acetabulum occurs
only on the horseshoe-shaped hyaline
cartilage on the periphery of the lunate
surface and articulates with the head of
⚫ The inferior aspect of the lunate surface (the base of the
horseshoe) is interrupted by a deep notch called the acetabular
notch.
⚫ The cavity of the acetabulum faces obliquely forward, outward,
and downward, and a malaligned acetabulum does not
adequately cover the femoral head, often causing chronic
dislocation and osteoarthritis.
⚫ The acetabulum is deepened by the fibrocartilaginous acetabular
labrum, which surrounds the periphery.
 Osteology of femur
⚫ The femur is the longest bone in the
body which forms the thigh. The part
which articulates with the pelvis to
form the hip joint is known as the
head of the femur.
⚫ The main function of the surfaces of
both the head of the femur and the
acetabulum are covered with a thin
layer of hyaline cartilage which acts to
allow smooth movement of the joint.
FEMORAL HEAD
⚫ l. Rydell (1965) suggested that most
load was transmitted in the femoral
head through the superior quadrant.
⚫ The articular cartilage covering the femoral head is thickest on
the medial-central surface surrounding the fovea into which the
ligamentum teres attaches and thinnest toward the periphery.
⚫ The load-bearing area is concentrated at the periphery of the
lunate surface of the femoral head at smaller loads, but it shifts to
the center of the lunate surface and the anterior and posterior
horns as loads increase .
 FEMORAL NECK
⚫ The femoral neck has two angular relationships with
the femoral shaft that are important to hip joint
function:
The angle of inclination of the neck to the shaft in the
frontal plane (the neck-to-shaft angle)
The angle of Torsion in the transverse plane
 Angle of
inclination-
⚫ Angle within the frontal plane between the NOF &
medial side of femoral shaft. (angle between the axis
through the femoral head and neck and the axis
through the femoral shaft)
At birth 140˚-150˚
Normal value : 125˚
• Significance : this angle provides optimal alignment of
the joint surfaces.
•
An angle greater than 125° produces a condition known
as coxa valga, while an angle less than 125° is known as coxa
vara .
 ANGLE OF TORSION
Angle of projection of the long axis of the femoral head
and the transverse axis of the femoral condyles.
The torsion angle reflects medial rotary migration of
the lower limb bud that occurs in fetal development; it is
commonly estimated at 40° in newborns, but decreases
substantially in the first two years of life.
A torsion angle of between 10° and 20° is considered
normal.
Angles greater than 20°, known as anteversion, cause a
portion of the femoral head to be uncovered and create a
tendency toward internal rotation of the leg during gait to
keep the femoral head in the acetabular cavity.
Retroversion, an angle of less than 12°, produces a
tendency toward external rotation of the leg during gait
 Ligaments of the hip joint
⚫ The stability of the hip owes greatly to the presence of its
ligaments : -
⚫ Iliofemoral ligament: This is a strong ligament which connects
the pelvis to the femur at the front of the joint.
- It resembles a Y in shape and stabilizes the hip by limiting
hyperextension
⚫ Pubofemoral ligament: The pubofemoral ligament attaches the
part of the pelvis known as the pubis (most forward part, either
side of the pubic symphesis to the femur )
⚫ Ischiofemoral ligament: This is a ligament which reinforces the
posterior aspect of the capsule, attaching to the ischium and
between the two trochanters of the femur.
 Muscles of the hip joint
⚫ Flexors:
Primary : Iliacus & Psoas Major
Associate : Pectinius , Rectus Femoris, Sartorius.
⚫ Extensors:
Primary: Gluteus Maximus
Associate: Hamstring
⚫ Abductors:
Primary : Gluteus Medius & Glutius Minimus
Associate: Tensor Fascia Latae & Sartorius
 Contd..
⚫ Adductors:
Primary : Adductor Brevis, Longus & Magnus.
Associate : pectineus & gracialis
⚫ Medial rotators:
Primary : Tensor Fascia Latae, Gluteus Medius & Minimus
Associate : Adductors
⚫ Lateral rotators:
Primary : Obturator Internus, Externus, Quadratus Femoris
Associate : Piriformis & Gluteus Maximus.
 Kinematics
⚫ If we are considering the kinematics of the hip joint, it is useful to see
the joint as a stable ball-and-socket configuration wherein the femoral
head and acetabulum can move in all directions.
⚫ Motion is maximum in the sagittal plane.
⚫ Hip motion takes place in all three planes:
Sagittal - Flexion-Extension
Frontal - Abduction-adduction
Transverse- Int. & ext. rotation
 ARTHROKINEMATICS

SLIDING ROLLING
SPINNING
 Arthrokinematics

⚫ During hip motion , femoral head remains snugly

seated into the acetabulum.

⚫ The steep wall of acetabulum , with acetabular

labrum , limits significant translation between the
joint surfaces.
⚫ Hip arthro kinematics are based on the traditional
convex-on-concave or concave on convex
principles
❖ Abduction and adduction
occur across the longitudinal
diameter of the joint surfaces.
❖ With the hip extended,
internal and external rotation
occur across the transverse
diameter of the joint surfaces.
❖ Flexion and extension occur as
a spin between the femoral
head and the lunate surfaces
of the acetabulum. The axis of
rotation for this spin passes
through the femoral head.
 OSTEOKINEMATICS

⚫ Describes the ROM allowed at hip including factors that permit

& restrict the ROM.
2 terms that describe ROM at hip:
⚫⚪ - Femoral on pelvic hip osteokinematics
Rotation of the femur in the sagittal plane
⚪ Rotation of the femur in the frontal plane
⚪
⚫ ⚪-Pelvic
Rotation of the femur in horizontal plane
on hip osteokinematics
Lumbopelvic rhythm
⚪ Pelvic on femoral rotation in sagittal plane
⚪ Pelvic on femoral rotation in horizontal plane
 ANGULAR MOTION OF FEMUR IN THE
SAGITTAL PLANE
⚫ On average, with the knee fully flexed, hip flexes to
120 deg.
⚫ With knee extended, hip is limited to 80 deg.
⚫ Full hip flexion slackens most ligaments but
stretches inferior capsule.
⚫ Hip normally extends to about 20 deg beyond
neutral position.
⚫ When knee is fully flexed during hip extension
passive tension in stretched rectus femoris reduces
hip extension to about neutral position.
⚫ Full hip extension increases passive tension in most
 ANGULAR MOTION OF FEMUR IN
FRONTAL PLANE
⚫ On average, hip abducts 40 deg. Limited
primarily by pubo-femoral ligament and
adductor & hamstrings muscle.
⚫ Hip adducts 25 deg beyond the neutral
position.
 Rotation of femur in horizontal plane
⚫ Hip internally rotates about 35 deg.
⚫ With hip fully extended, maximal internal
rotation elongates external rotator muscle.
⚫ In healthy adults hip external rotation
remains unchanged with hip flexion or
extension.
⚫ Extended hip externally rotates at about 45
deg.
⚫ Position of hip flexion decrease active
 Pelvis on femur osteokinematics
⚫ Lumbopelvic rhythm
⚫ Pelvic on femoral rotation in sagittal plane
⚫ Pelvic on femoral rotation in horizontal
plane
 Pevlic on femoral rotation in sagital plane
⚫ ANTERIOR & POSTERIOR PELVIC TILT:
⚫ Hip flexion can occur through a limited arc via an
anterior tilt on the pelvis over stationary femoral
heads.
⚫ Pelvic tilt is a sagittal plane rotation of the pelvis
relative to the femur.
⚫ Direction of the tilt is based on the direction of
rotation of a point on the iliac crest.
⚫ The anterior tilt of the pelvis occurs about a
mediolateral axis of rotation through both femoral
heads.
 Pelvis on femoral rotation in the frontal
plane
⚫ Occurs in frontal & horizontal plane & are best
described assuming a preparation is in standing
on one limb.
⚫ Weight bearing extremity is referred to as the
support hip.
⚫ Abduction of the support hip occurs by raising
or “hiking” the illiac crest on the side of non-
support hip.
⚫ Pelvic in femoral hip abduction is restricted to
⚫ Hip adduction of the support hip occurs by lowering
of the illiac crest on the side of non- support hip.
⚫ This motion causes a slight lateral concavity with the
lumbar region on the side of the adducted hip.
 Pelvic on femoral rotation in the horizontal plane

⚫ Occurs about a longitudinal axis of rotation.

⚫ Internal rotation of the support hip rotates

forward in the horizontal plane.

⚫ External rotation is the contrast of the above.

 Pelvifemoral Motion

⚫ When the pelvis moves on a relatively

fixed femur, there are two possible
outcomes to consider.
⚪ The head and trunk will follow the
motion of the pelvis (moving the
head through space)
⚪ The head will continue to remain
relatively upright and vertical
despite the pelvic motions.
⚫ The specific rhythm varies among individuals, but flexion of the
trunk from standing combines flexion of the lumbar vertebrae and
at the lumbosacral junction with forward rotation of the pelvis on
the fixed femora.
⚫ This femur, pelvis, and spine move in a coordinated manner to
produce a larger ROM than is available to one segment alone. Thus
the hip joint is participating in what will predominantly (but not
exclusively) be an open-chain motion termed “Pelvifemoral
motion”.
⚫ In the case of pelvifemoral motion, the joints may serve either end
of the chain: the foot or head.
 Lumbopelvic Rhythm during Trunk Flexion and
Extension
⚫ In conjunction with the hip joints, the lumbar spine provides the major
flexion and extension pivot point for the human body as a whole.
⚫ The kinematic relationship between the lumbar spine and hip joints
during such sagittal plane movements has been referred to as
lumbopelvic rhythm.
Variations of Lumbopelvic Rhythms during Trunk Flexion from a
Standing Position:
⚫ Consider the common action of bending forward toward the ground
while keeping the knees nearly straight.
⚫ If the knees remain extended, the hips will typically flex no more than 90
so isolated flexion at the hip joints (anteriorly tilting the pelvis on the
femurs) is generally insufficient to reach the ground.
⚫ The addition of flexion of the lumbar spine (and, perhaps, flexion of the
thoracic spine) will add to the total ROM
⚫ This motion in the healthy adult has been measured as a
combination of about 40 degrees of lumbar flexion performed
nearly simultaneously with about 70 degrees of hip (pelvic-on-
femoral) flexion.
⚫ Thus combination of hip and trunk flexion is generally sufficient for
the hands to reach the ground—as long as the hamstrings and
lumbar extensors allow sufficient lengthening.
⚫ Any deviation from this pattern may help distinguish pathology or
impairments affecting the lower spine from those affecting the hip
joints.
 FIG(B). WITH LIMITED HIP FLEXION FROM
(Bending the trunk toward the floor)
For example restricted hamstring extensibility,

Requires greater flexion in the lumbar and lower thoracic spinal regions.

Overstretch and subsequently weaken the posterior connective tissues within

the region (including the thoracolumbar fascia)

Reducing the ability of these tissues to limit further flexion

A chronic posture of increased flexion of the lumbar spine places a

disproportionally larger compressive load on the intervertebral discs,

Theoretically increasing their likelihood for degeneration.

 FIG C :FLEXION OF THE LUMBAR SPINE IS LIMITED

Requires disproportionally greater flexion of the hips,

Creating greater demands on the hip extensor muscles

The hip joints are subjected to greater compression loads.

⚫ In persons with healthy hips, this relatively low level increase in

compression force is usually well tolerated.
⚫ In a person with a preexisting hip condition (such as osteoarthritis or hip
instability), however, the increased compression force
 Lumbopelvic Rhythm during Trunk Extension from a
Forward Bent Position:

⚫ The typical lumbopelvic rhythm used to extend the trunk from a

forward bent position is depicted in a series of consecutive
phases.
⚫ Extension of the trunk with knees extended is often initiated by
extension of the hip joints .
⚫ This is usually followed after a short delay by extension of the
lumbar spine
⚫ This short delay in lumbar extension places greater extension
torque demands on the powerful hip extensor muscles (such as
the hamstrings and gluteus maximus) at the time when the
external flexion torque on the lumbar region is greatest.
⚫ This may be a beneficial strategy to naturally protect the low-back
muscles and joints from large forces.
 Kinetics
⚫ Kinetic studies have shown that the substantial forces act
on the hip joint during simple activities of the hip.
The study of hip kinetics has divided into two part :-
1) static
2) Dynamic
During a two-leg stance, the line of gravity passes
posterior to the pubic symphysis, and, because the hip
joint is stable, an erect stance can be achieved without
muscle contraction through the stabilizing effect of the
joint capsule and capsular ligaments. With no muscle
activity to produce moments around the hip joint.
TRABECULAR SYSTEM
⚫ The medial (or principal compressive) trabecular system arises
from the medial cortex of the upper femoral shaft and radiates
through the cancellous bone to the cortical bone of the superior
aspect of the femoral head. The medial system of trabeculae is
oriented along the vertical compressive forces passing through the
hip joint.
⚫ The lateral (or principal tensile) trabecular system of the femur
arises from the lateral cortex of the upper femoral shaft and, after
crossing the medial system, terminates in the cortical bone on the
inferior aspect of the head of the femur. The lateral trabecular
system is oblique and may develop in response to parallel (shear)
forces of the weight of HAT and the GRF.
⦿ There are two accessory (or secondary) trabecular systems, of
which one is considered compressive and the other is considered
tensile. Another secondary trabecular system is confined to the
trochanteric area femur.
⦿ The areas in which the trabecular systems cross each other at right
angles are areas that offer the greatest resistance to stress and
strain. There is an area in the femoral neck in which the
trabeculae are relatively thin and do not cross each other. This
zone of weakness has less reinforcement and thus more potential
for failure. The zone of weakness of the femoral neck is
particularly susceptible to the bending forces across the area and
can fracture either when forces are excessive or when
compromised bony composition reduces the tissue’s ability to
⚫ Figure . Schematic showing the direction and magnitude of
the load on the femoral head in symmetrical two-leg stance.
 HIP JOINT FORCES AND MUSCLE
FUNCTION IN STANCE
Bilateral Stance
⚫ In erect bilateral stance, both hips are in neutral or slight
hyperextension, and weight is evenly distributed between both
legs. The line of gravity falls just posterior to the axis for flexion/
extension of the hip joint. The posterior location of the line of
gravity creates an extension moment of force around the hip
that tends to tilt the pelvis posteriorly on the femoral heads.
⚫ The gravitational extension moment is largely checked by
passive tension in the hip joint capsuloligamentous structures,
although slight or intermittent activity in the iliopsoas muscles
in relaxed standing may assist the passive structures.
⚫ In the frontal plane during bilateral stance, the superincumbent
body weight is transmitted through the sacroiliac joints and
pelvis to the right and left femoral heads.
⚫ The weight of the HAT (two thirds of body weight) should be
distributed so that each femoral head receives approximately half
of the superincumbent weight.
⚫ The joint axis of each hip lies at an equal distance from the line of
gravity of HAT; that is, the gravitational moment arms for the right
hip (DR) and the left hip (DL) are equal. Because the body weight
(W) on each femoral head is the same (WR & WL), the magnitude of
the gravitational torques around each hip must be identical (WR *
DR =WL* DL).
⚫ The gravitational torques on the right and left hips, however, occur
in opposite directions. The weight of the body acting around the
right hip tends to drop the pelvis down on the left (right adduction
moment), whereas the weight acting around the left hip tends to
drop the pelvis down on the right (left adduction moment).
⚫ These two opposing gravitational
moments of equal magnitude balance
each other, and the pelvis is
maintained in equilibrium in the
frontal plane without the assistance
of active muscles.
⚫ Assuming that muscular forces are
not required to maintain either
sagittal or frontal plane stability at
the hip joint in bilateral stance, the
compression across each hip joint in
bilateral stance should simply be half
the superimposed body weight (or
 Unilateral stance
⚫ If the left leg has been lifted from the ground and the full
superimposed body weight (HAT) is being supported by the right
hip joint.
⚫ Rather than sharing the compressive force of the superimposed
body weight with the left limb, the right hip joint must now carry
the full burden. In addition, the weight of the non-weight bearing
left limb that is hanging on the left side of the pelvis must be
supported along with the weight of HAT.
⚫ Of the one third of the portion of body weight found in the lower
extremities, the non-weight bearing limb must account for half of
that, or one sixth of the full body weight.
⚫ The magnitude of body weight (W) compressing the right hip joint
⚫ In our hypothetical subject from
Example who weighs 825 N, HAT
accounts for 550 N. One lower
extremity weighs one sixth of body
weight, or 137.5 N. Therefore, when
this individual lifts one leg off the
ground, the supporting hip joint will
undergo 687.5 N (or five sixths of
body weight) of compression from
body weight alone.
⚫ Although we have accounted for the
increase in hip joint compression
from body weight as a person moves
from double-limb support (bilateral
stance) to single-limb support, the
problem is more complex. Not only is
the hip joint in unilateral stance
being compressed by body
weight(gravity), but also that body
⚫ The force of gravity acting on HAT and the non weight bearing left
lower limb (HATLL) will create an adduction torque around the
weight-bearing hip joint; that is, gravity will attempt to drop the
pelvis .
⚫ The abduction counter-torque will have to be supplied by the hip
abductor musculature.
⚫ The result will be joint compression or a joint reaction force that is
a combination of both body weight and abductor muscular
compression.
⚫ The total joint compression can be calculated for our hypothetical
825-N subject. The line of gravity of HATLL can be estimated to lie
10 cm (0.1 m, or ~4 in.) from the right hip joint axis. That is, the
moment arm (MA) = 0.1 m, although the actual distance will vary
among individuals.
Compensatory Lateral Lean of
the Trunk
⚫ Gravitational torque at the pelvis is the
product of body weight and the distance
that the line of gravity lies from the hip
joint axis (its moment arm).
⚫ If there is a need to reduce the torque of
gravity in unilateral stance and if body
weight cannot be reduced, the moment
arm of the gravitational force can be
reduced by laterally leaning the trunk
over the pelvis toward the side of pain or
weakness when in unilateral stance on the
painful limb.
⚫ Although leaning toward the side of pain
might appear counterintuitive, the
compensatory lateral lean of the trunk
toward the painful stance limb will swing
the line of gravity closer to the hip joint,
thereby reducing the gravitational
 Use of a Cane Ipsilaterally
⚫ Pushing downward on a cane held in the hand on the side of pain
or weakness should reduce the superimposed body weight by the
amount of downward thrust; that is, some of the weight of HATLL
would follow the arm to the cane, rather than arriving on the
sacrum and the weight-bearing hip joint.
⚫ Inman and colleagues suggested that it is realistic to expect that
someone can push down on a cane with approximately 15% of his
body weight. The proportion of body weight that passes through
the cane will not pass through the hip joint and will not create an
adduction torque around the supporting hip joint.
⚫ Total hip joint compression of 1,691.35 N calculated, when a cane
is used ipsilaterally provides some relief over the total hip joint
compression of 2,062.5 N ordinarily experienced in unilateral
⚫ compression when the cane is used ipsilaterally is still greater,
however, than the total joint compression of 1,031.25 N found with
a compensatory lateral trunk lean.
⚫ Although a cane used ipsilaterally provides some benefits in energy
expenditure and structural stress reduction, it is not as effective in
reducing hip joint compression as the undesirable lateral lean of
the trunk.
⚫ Moving the cane to the opposite hand produces substantially
different and better results.
 Use of a Cane Contralaterally

⚫ When the cane is moved to the side

opposite the painful or weak hip joint,
the reduction in the magnitude of
HATLL is the same as it is when the cane
is used on the same side as the painful
hip joint; that is, the superimposed body
weight passing through the weight-
bearing hip joint is reduced by
approximately 15% of body weight.
⚫ However, the cane is now substantially
farther from the painful supporting hip
joint than it would be if the cane is used
on the same side; that is, in addition to
relieving some of the superimposed
body weight, the cane is now in a
position to assist the abductor muscles
in providing a counter torque to the
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