The document discusses the anatomy and biomechanics of the hip joint. It describes the ball and socket structure of the hip joint formed by the acetabulum and femoral head. It details the angles of the hip joint including the central edge angle and angle of anteversion. It discusses the muscles, ligaments, biomechanics including ranges of motion, and forces across the hip joint during activities like standing, walking, and squatting. Pathomechanics of conditions like hip fractures and dislocations are also mentioned.

1. HIP JOINT
ANATOMY
BIOMECHANICS AND
PATHOMECHANICSBy Dr. Radhika Chintamani

2. CONTENTS
 Functional Anatomy
 Angles of Hip joint
 Trabecular system
 Hip joint stability factors
 Alignments of articulation
 Myology
 Kinematics
 Pelvic Femoral rhythm
 Joint force system
 Pathology and pathomechanics

3. FUNCTIONAL ANATOMY OF HIP
Functional Anatomy:
 Hip joint is a ball and socket joint with articular surfaces;
acetabulum of the innominate (pelvis) bone and head of femur.

4. a) Acetabulum:
 It’s a concave shaped structures present in the hip bone, which is
horse shaped because of presence of acetabular notch.
 Faces forward, outward and slightly downward direction.
 The orientation of the acetabulum influences the mobility of the hip
and the location of weight-bearing forces on the femoral head.
 Weight bearing at the hip joint involves the thicker superior and
peripheral aspects of the acetabulum, while the thin, central,
deepest part of the socket is unsuited for weight bearing. Well-
organized arrays of trabecular bone surrounding the acetabulum,
but particularly superior to it, reinforce the weight-bearing capacity
of the socket

5. ANGLES OF HIP JOINT
 Angles contributing to the surface of attachment of
acetabulum to the femoral head are:
i. Central edge angle/ angle of wisberg
ii. Angle of anteversion

6. i. Central edge angle (Wiberg’s
angle): angle formed between
the centre of the femoral head
and the line connecting lateral
rim of acetabulum.
 Assess inferior tilt of the
acetabulum with respect to the
femur.
 Adna and associates found CE
angle in afults to avg about
380=men and 350=women, with
range=220-420.

7. ii. Angle of torsion: formed by line drawn
from long axis of femur and line parallel
to dorsal aspect of femoral condyles.
Refers to magnitude of anterior
orientation of acetabulum.
 Adna and associates found average
value to be
men=18.50,
women=21.50
F>M{due to wide pelvis}
Pathology :
 angle>150
=DDH
 angle<80
=Femoro-acetabular
impingement.
Compensatory hip medial rotation
due to excessive anteversion

8. Angle of Torsion
 Transverse plane angle.
 Formed by an axis through femoral condyle and the axis through
head and neck of the femur. The angle at which these two line
bisect is known as angle of torsion.
 It represents medial rotatory migration of the lower limb that
occurred during fetal development.
 Decreases with age.
 In adult Normal angle=10-20degs.
 Increased angle=anteversion
 Decreased angle=retroversion.

9. b) Femoral head:
 Shape: Ellipsoid.
 Articular cartilage covering the head is thickened in the meadian-cental
third and peripherally the cartilage is thin. This cartilage covers overall
the head of femur except the fovea capitis which is the central part of
the head of femur, where the ligamentum teres has its attachment.
 Arterial supply to the femoral head is by three artery those are as
follows:
 Foveal artery
 Retinacular artery
 Medullary artery.
 Angles related to the head of the femur are:
i. Angle of inclination
ii. Angle of retroversion

10. i. Angle of inclination: Angle made by
the line drawn through the neck and
head of femur passing through the fovea
capitis, and the line drawn through the
shaft of the femur. (medial angle).
 Frontal plane angle
 Normal angle range=115 to 140
 Men>women(wider pelvis in women).
 Normal angle of inclination=GT lies at
the level of center of femoral head.
 Increase in angle=coxa valga
 Decrease in angle=coxa vara
A= Normal
B= Abnormal

11. ACETABULAR LABRUM
 Provides proprioception and pain sensitivity that may
help protect the rim of the acetabulum.
 Also enhances joint lubrication

12. HIP JOINT AS WHOLE
 The bones of the hip joint are generally congruent with each other,
and the congruency is improved even more by the articular
cartilage. This congruency provides two important benefits.
 First, the congruency allows larger areas of the joint to articulate
with one another throughout the natural ROM of the hip. This
means that the loads sustained during weight bearing can be
spread across larger surface areas, thus reducing the stress
(force/area) the joint must withstand.
 The congruency facilitates stability of the joint throughout the
ROM.

13. JOINT SURFACES
 Hip joint is a congruent ball
and socket, synovial joint.
 Femoral articular
surface>acetabulum.
 In standing the anterior and
superior part of the femoral
head is not covered by the
acetabulum.
 There is complete articulation
between both joints in non-
weight bearing position by
combination of flexion,
abduction and slight lateral
rotation( frog-leg position)

14. CAPSULOLIGAMENTOUS STRUCTURES
OF THE HIP JOINT.
A) Capsule of the hip joint:
 Weaker capsule when compared with shoulder.
 Irregular, Surrounds entire hip joint and is thickened antero-
superiorly where primary stresses occur, relatively thin and
loose postero-inferiorly.
 Femoral neck is intracapsular, where both GT and LT are
extracapsular.

15. LIGAMENTS OF HIP JOINT
Ligaments
Intracapsular
Ligamentum Teres
Transverse acetabular ligament Extracapsular
Illiofemoral
Pubofemoral
Ishciofemoral
Orbicular Zone

16. INTRACAPSULAR LIGAMENTS
i. Ligamentum Teres:
 Also known as round ligament of head of femur.
 Extra-synovial accessory joint structure.
 Attachment: peripheral edge of acetabular notch to
the fovea capitis.
 Importance: provides pathway to the foveal artery to
enter the head of femur.
 Becomes tensed on: semiflexion and adduction of hip.

17. ii. Transverse acetabular ligament:
 Attachment: between antero-inferior and postero-inferior
aspects of acetabulum
 Function: protection of blood vessels travelling beneath it to
reach the head of femur.

18. EXTRACAPSULAR LIGAMENTS
i. Illiofemoral ligament:
 Also known as ”Y” ligament (because of its inferior attachment which is in a shape
of ’Y’), and ligament of Bigelow, who stated that this ligament provides major part
of stability to the hip joint.
 Reinforces capsule anteriorly.
 Attachment: anterior inferior iliac spine to intertrochanetric line and lesser
trochanter.
 Function: resists hyperextension and external rotation of stance leg.
ii. Pubofemoral ligament:
 Reinforces the fibrous capsule inferiorly.
 Attachment: pubic portion of the acetabular rim and pubic symphysis to neck of
femur.

19. iii. Ischiofemoral:
 Reinforces the capsule posteriorly
 Attachment: ischial portion of acetabular rim to the neck of
femur and medial side base of GT.
Function: resist extension and medial rotation.

20. TRABECULAR SYSTEM OF THE FEMUR
 Function ： to accommodate to the mechanical stresses and strains
created by the transmission of forces between femur and pelvis
 Classification :
 Medial or primary
compressive system
 Lateral or principle
tensile system

21. Accessory trabecular system
o Medial accessory
o Lateral accessory & trochanter system
 zone of weakness
o The area where the trabecular do not cross at right angles
o Less reinforcement
by trabecular
o More potential for injury

22.  The medial and lateral trabecular arrays of bone
found in the proximal femur appear well aligned to
resist these compressive and tensile forces,
respectively, protecting the femoral neck from the
bending moment that could sever the femoral head
from the neck.

23. CLINICAL IMPORTANCE
 Depending on the trabecular presence or
reabsorbed, Singh's index is classified for
osteoporosis of hip. The disease which usually
occurs in old age.

24. CLINICAL IMPORTANCE
 Also, depending on the alignment of the trabeculae
and its bending, garden’s classification of the
intertrochanteric fracture can be classified.

25. HIP JOINT STABILITY
Hip is stabilized by
1. Bony configuration.
2. Capsule: As the hip is extended, the fibers of the capsule clamp
down on the bony contents within, firmly holding the femoral head in
the acetabulum (Fig. 38.11). In contrast, hip flexion slackens the
joint capsule.
3. Strong reinforcing ligaments.
4. Negative Intra-articular pressure

26. CLINICAL RELEVANCE
 As hip flexion slackens the capsule covering the hip joint
which is a major static stabilizer of the hip, in dash-board
injury, the person is in sitting position (slackened hip joint
capsule + high trauma from the dashboard (directed
posteriorly) posterior dislocation of the hip.

27. HIP JOINT: FLEXOR CONTRACTURES
Inflammation of the Hip due to various reasons like RA and
other infections
Irritation of the capsule and the surrounding structures to
the joint
Capsule inflammation
To relieve pain patient often assumes position of hip flexion
Prolonged maintained hip flexion in order to relieve pain
Flexor contracture.

28. ALIGNMENTS OF ARTICULATION
 In normal erect posture, the acetabulum and femoral head are
aligned so that the head of the femur is directed slightly anteriorly
and superiorly in the acetabulum. This orientation exposes the
anterior aspect of the femoral head, leaving a large articular surface
available for movement toward flexion.
 The orientation of the femur and acetabulum facilitates advancement
of the thigh in front of the trunk (flexion), while limiting the potential
for backward movement of the thigh beyond the trunk. Flexion and
abduction of the hip move the femoral head toward the deepest part
of the acetabulum.

29.  The joint reaction force on the normal
proximal femur (head of femur) during
upright standing is more vertically
aligned than the femoral neck, creating
a bending moment on the head and
neck of the femur.
 This bending moment produces tensile
forces on the superior aspect of the
femoral neck and compressive forces
on the inferior aspect of the neck (Fig).
 Femoral necks with a wider superior to
inferior diameter are better able to
withstand the bending moments
sustained during weight bearing.
 Men have wider femoral necks than
women, which may help explain why
the incidence of femoral neck fractures
is much higher in women.

30. CLINICAL RELEVANCE
 On standing: bilateral femoral head takes about
2/3rd
of total body’s weight individually.
 On unilateral standing it takes around= 1/3rd
extra of
the swing limb added=2/3rd
+ 1/3rd
.

31. FEMORAL ALIGNMENT CONTINUED..
 Intrinsic alignment of the femur is an important element in
the relationship between the femur and acetabulum. The
femoral head is directed toward the superior and anterior
aspect of the acetabulum, resulting from the angle of
inclination between the femoral neck and shaft in the
frontal plane and the transverse plane orientation of the
femoral neck.

32. MYOLOGY OF HIP
 Hip flexor:
1. Ilipsoas together
2. Rectus femoris
 Hip extensor:
1. Gluteus maximus
2. Hamstrings
Hip abductors:
3. Gluteus medius
4. Tensor fascia lata
Hip Adductors
5. Adductor group of muscles.
Hip Internal rotators:
6. Piriformis
 Hip Internal rotator:
1. Piriformis
2. Gluteus minimus
 Hip external rotator:
1. Piriformis
2. Tensor fascia lata
3. Quadratus femoris
4. Oburator internus
5. Gemelli

33. KINEMATICS OF THE HIP
 Hip Flexion/ Extension ·
 Plane of motion ： sagittal plane
 Axis of rotation ： a frontal axis passing through the center of the
head of the femur
 Osteokinematic movements
 Range of motion (ROM)
 Hip flexion ： 0-90º with knee extension
0-1200
when knee flexed
 Hip extension ： 0-45º

34.  Closed kinematic chain motions
 Deep squatting
 Stance phase of the gait cycle
 Cycling
 Arthrokinematic movements (convex on concave)
Hip flexion ： spin with slightly posterior glide of the femoral head
on the acetebulum
Hip extension ： spin with slightly anterior glide of the femoral head
on the acetabulum

35. Hip Abduction
 Plane of motion ： frontal plane
 Axis of rotation ： a sagittal axis passing through the center of the
head of the femur osteokinematic movements
 Range of motion (ROM) ： 0-40º
 Closed kinematic chain motions ： to maintain a level pelvis in
unilateral stance

36. Arthrokinematic movements (convex on concave)
Hip abduction ： inferior glide of the femoral head on the acetebulum
Hip Internal/ External Rotation
 Plane of motion ： transverse plane
 Axis of rotation ： a vertical axis passing through the center of the
head of the femur

37. Osteokinematic movements
Range of motion (rom)
· internal rotation ： 0-40º
· external rotation ： 0-45º
 Arthrokinematic movements (convex on concave)
 Hip internal rotation ： posterior glide of the femoral head on the
acetebulum
 Hip external rotation ： anterior glide of the femoral head on the
acetebulum

38. MOTION OF THE PELVIS ON FEMUR
 Anterior and posterior pelvic tilt
diagram

39.  Lateral pelvic tilt the axis of motion is
around stance hip
 Anterior and posterior the reference is opposite
pelvic tilt side pelvic
This occurs due to the moment arm of the gluteus medius muscle. the
gluetus medius muscle acts to stabilize the opposite pelvis along with
abduction of the ipsilateral femur.

40. Coordinated motions of femur ,pelvis
and lumbar spine
Pelvifemoral motion or rhythm
 Can be considered similar to glenohumeral rhythm. The only difference is;
it not only helps in improvement of ROM of lower extremity but also
helps to asssit in lumbo-pelvic rhythm. Hence, lumbo-pelvic rhythm and
pelvic femoral rhythm goes hand in hand.
 Whenever the hip joint is weight bearing and movement should be carried
out by the hip such as squatting, the pelvis moves on the fixed femur.
 Anterior and posterior tilting of the pelvis on the fixed femur produce hip
flexion and extension of hip joint respectively. Hip joint extension through
posterior pelvic tilting brings the symphysis pubis and sacrum of the pelvis
closer to the femur rather than moving the femur posteriorly on the pelvis.

41. Coordinated motions of femur ,pelvis and lumbar spine
Pelvifemoral motion or
rhythm
 In open kinetic chain
movement such as hip flexion
in standing; posterior pelvic
tilt assists in the movement.

42. HIP JOINT FORCES AND MUSCLE FUNCTION IN
STANCE
Sagital plane
Cont..d

44. Unilateral stance: Due to relaxation
of the gluteus medius muscle on
contralateral side to leg lifted up
Bilateral stance: both gluteus medius
are active thus, stability of pelvis is
maintained

45. REDUCTION OF MUSCLE FORCE IN UNILATERAL
STANCE
 Compensatory lateral lean of the
trunk
 Use of cane
 Ipsilaterally
 Contralaterally
 Adjustment of carrying loads---to
pain or weakness side
If, gluteus medius msucle is
weak.

46. FEMORAL ALIGNMENT
DYSFUNCTIONS
 Coxa Valga:
 As stated earlier, the angle of inclination is typically reported
to be 125°. Coxa valga results when the angle between the
neck of femur and the shaft is greater than 1250.
 Evidence:
 Yoshioka et al. report an average angle of 131°in a sample
of 32 cadaver specimens [72].
 A hip with an excessive frontal plane angle is said to have a
coxa valga deformity, or valgus deformity of the hip.
HIP PATHOLOGY AND PATHOMECHANICSHIP PATHOLOGY AND PATHOMECHANICS

47. CLINICAL IMPORTANCE
 Coxa valga cause a # known as wall #. In this #, the
femoral head is displaced superiorly breaking the
acetabulum in the pelvic cavity (due to
degeneration of the acetabulum as the compressive
load is increased on the acetabular surface.

48. FEMORAL ALIGNMENT
DYSFUNCTIONS
 Coxa Vara:
 The angle of inclination is typically reported to be 125°.
Coxa valga results when the angle between the neck of
femur and the shaft is lesser than 1250.
 Evidence: Carpintero et al. suggest that coxa vara is a risk
factor for stress fractures of the femoral neck.
 A hip with reduced frontal plane angle is said to have a
coxa varaa deformity, or varus deformity of the hip.

49. CLINICAL IMPORTANCE
 Increased weight bearing in the coxa vara leg,
leads to increased compressive load on the femoral
head, which crosses the acetabular limit causing
the displacement of the femoral head inferiorly.

50. BIOMECHANICAL ADVANTAGES IN THE HIP JOINT DEFORMITIES
 The joint reaction force on the
femur is more parallel to the
femoral neck in coxa valga. This
alignment subjects the femoral
neck to more compressive forces
and less of a bending moment
leading to arrangement of
cancellous bone in column
parallel to the neck
 The perpendicular distance
between the hip joint center and
the trochanter is decreased in
coxa valga, putting the hip
abductor muscles at a
disadvantage by reducing their
moment arm. With decreased
moment arms, the hip abductor
muscles must generate larger
contractile forces to support the
hip joint, resulting in increased
joint reaction force.
 The joint reaction force on the
femur is more parallel to the
femoral neck in coxa valga. This
alignment subjects the femoral
neck to more compressive forces
and less of a bending moment
leading to arrangement of
cancellous bone in column
parallel to the neck
 The perpendicular distance
between the hip joint center and
the trochanter is decreased in
coxa valga, putting the hip
abductor muscles at a
disadvantage by reducing their
moment arm. With decreased
moment arms, the hip abductor
muscles must generate larger
contractile forces to support the
hip joint, resulting in increased
joint reaction force.
 The increased bending moment
increases the compressive forces
on the medial aspect of the
femoral neck and the tensile
forces laterally, leading to an
increase in the medial and lateral
trabecular arrays.
 In addition, a coxa vara deformity
moves the trochanter farther from
the joint center, effectively
lengthening the moment arm of
the hip abductors. This puts the
hip abductors at a mechanical
advantage and may actually
reduce the force they are
required to exert during stance,
thus reducing the joint reaction
force.
 The increased bending moment
increases the compressive forces
on the medial aspect of the
femoral neck and the tensile
forces laterally, leading to an
increase in the medial and lateral
trabecular arrays.
 In addition, a coxa vara deformity
moves the trochanter farther from
the joint center, effectively
lengthening the moment arm of
the hip abductors. This puts the
hip abductors at a mechanical
advantage and may actually
reduce the force they are
required to exert during stance,
thus reducing the joint reaction
force.
Coxa Valga Coxa Vara

51. BIOMECHANICAL ADVANTAGES IN THE HIP JOINT DEFORMITIES
 In addition, the joint reaction
force is displaced laterally in
the acetabulum and is applied
over a smaller joint surface,
leading to increased joint
stress. In other words, coxa
valga deformities are likely to
increase the risk of
degenerative joint disease
within the hip by increasing the
joint reaction force as well as
the stress sustained by the
femoral head.
 In addition, the joint reaction
force is displaced laterally in
the acetabulum and is applied
over a smaller joint surface,
leading to increased joint
stress. In other words, coxa
valga deformities are likely to
increase the risk of
degenerative joint disease
within the hip by increasing the
joint reaction force as well as
the stress sustained by the
femoral head.
 However, coxa vara tends to
increase the medial pull on the
femur into the acetabulum, which
may contribute to erosion of the
acetabulum. Additionally, an
increased advantage for the
abductor muscles may be
accompanied by fatigue in the
antagonist muscles [5]. The
moment arm of the joint reaction
force may also be increased with
a net result of an increased
bending moment on the femoral
neck
 However, coxa vara tends to
increase the medial pull on the
femur into the acetabulum, which
may contribute to erosion of the
acetabulum. Additionally, an
increased advantage for the
abductor muscles may be
accompanied by fatigue in the
antagonist muscles [5]. The
moment arm of the joint reaction
force may also be increased with
a net result of an increased
bending moment on the femoral
neck
Coxa Valga Coxa Vara

52. NOTE
 In coxa valga, cancellous bone in the femoral neck
appears to be arranged in columns parallel to the
neck rather than in the medial and lateral
intersecting bundles seen in well-aligned femora.
 Coxa vara: Orthopaedic surgeons use the positive
effect of altering the femoral neck alignment and
improving the mechanical advantage of the
abductor muscles in surgical osteotomies to reduce
the loads on the hip for treatment of osteoarthritis
and aseptic necrosis.

53. HIPARTHROSIS (OA)
Primary cause ------------- Idiopathic
Secondary causes----- Trauma
Malalignment
Impingment b/n labrum and femur
 Common on periphery of head due to inadequate compressive forces

54. SLIPPED CAPITAL FEMORAL
EPIPHYSIS
 A slipped capital femoral epiphysis is a gradual or sudden
inferior and posterior displacement of the epiphysis, or growth
plate at the base of the femoral head.
 The mechanisms producing a slipped capital epiphysis help to
illustrate the changes in femoral loading with coxa valga and
coxa vara.
 Unlike the adult, the newborn possesses a femoral neck–shaft
angle that is significantly larger than 125°. In other words, coxa
valga is the “normal” alignment of the hip at birth. This valgus
alignment gradually decreases to normal adult values
throughout growth.

55. SLIPPED CAPITAL FEMORAL EPIPHYSIS
 During early development when the femoral neck has a maximum
valgus alignment, the epiphyseal plate of the femoral head (capital
femoral epiphysis) lies approximately perpendicular to the joint reaction
force on the head of the femur. In this position the joint reaction force
applies a compressive force on the epiphysis. As the valgus decreases,
the growth plate lies more oblique to the joint reaction force.
Consequently, the joint reaction force exerts both compressive and
shear forces on the epiphyseal plate.
 As the obliquity of the epiphysis increases, the shear force on it also
increases. The shear force tends to slide the head of the femur off the
epiphysis.
 If the shear force exceeds the strength of the growth plate, a slipped
capital epiphysis results. This disorder is seen most often in adolescent
males. Although hormonal imbalances have been implicated in the
development of slipped capital epiphysis, other factors including obesity
and sudden growth spurts are significant contributors as well, since
these increase the joint reaction force and its shear component.

56. GROIN PAIN
 Groin pain is typically associated with intraarticular
hip conditions such as capsulitis, chondritis, and
osteoarthritis, also SIJ dysfunction.

57. ANTEVERSION /RETROVERSION
Anteversion
 Reduces hip joint stability
 Hip abd. Line posterior to joint line
 Reduces MA for abd.
 Ant.capsular &musculature push head back causing total femoral
medial rotation
 Initially toe-in gait ,later with lateral rotation toe-out gait
Reverse with retroversion

58. THANK YOU