biomechanics of lower extremity complete

1. The Biomechanics of the
Human Lower Extremity
Dr Dileep Kumar
DPT,MSPT,MPPTA
CSMT,COMC,

2. Hip joint
One of the largest and most stable
joint:
The hip joint
Rigid ball-and-socket configuration
(Intrinsic stability)

4. The femoral head
Femoral head : convex component
Two-third of a sphere
Cover with cartilage
Rydell (1965) suggested :
most load----- superior quadrant

5. Acetabulum
Concave component of
ball and socket joint
Facing obliquely forward,
outward and downward
Covered with articular
cartilage
Provide with static
stability

6. Ligaments
•Iliofemoral ligament: Y shaped extremely
strong= anterior stability
•Pubofemoral ligament: anterior stability
•Ischiofemoral ligament: posterior
stability
•Ligamentum teres: Provides direct
attachment from rim of acetabulum to head
of femur.

7. Bursae
Iliopsoas bursae: b/w iliopsoas
and articular capsule.
Deep trochanteric: b/w greater
trochanter and G.Max

8. Tension in these ligaments acts to twist
the head of femur into acetabulum during
hip E, as person moves from sit to stand.

11. Structure of the Hip
The pelvic girdle includes the two ilia and
the sacrum. It can be rotated forward,
backward, and laterally to optimize
positioning of the hip.
Femoral
head
Femur
Acetabulum
Ilium
Sacrum
Pubis
Ischium

12. Movements at the Hip
Flexion
• iliacus
• Psoas Major
• Assisted by:
• Pectineus
• Rectus femoris
• Sartorius
• Tensor fascia latae

14. Both are two joint muscles
RF works more effectively as a hip flexor when knee is in F, kick..
Sartorius or tailors' muscle is longest muscle of body..

15. Movements at the Hip
Extension
•Gluteus maximus
•Hamstrings
• Biceps Femoris
• Semimembranosus
• Semitendinosus

16. G.Max
G.Max is massive ,powerful muscle that is usually active only when
hip is in Flexion as stairs climbing or when extension is resisted.

17. Movements at the Hip
abduction at the hip joint
• gluteus medius
• assisted by:
• gulteus minimus

18. Hip abductors
Contraction of the hip abductors is required during swing phase of
gait to prevent the swinging foot from dragging.
They stabilize the pelvis during support phase of walking.
Active during the performance of dance movements such as grand
ronde jambe .

19. Movements at the Hip
adduction at the hip joint?
• adductor magnus
• adductor longus
• adductor brevis
• assisted by:
• gracilis

20. Hip Adductors
 Crossing joint medially.
 Regularly active during swing
phase of gait cycle to bring the
foot beneath the body’s COG
during support phase.
 More active during stairs and
hill climbing.
 Gracilis also contribute to
flexion at knee.
 Other three adductors
contribute to flexion and LR at
hip when the femur is MR.


21. Movements at the Hip
lateral rotation
•Piriformis
•Gemellus superior
•Gemellus inferior
•Obturator internus
•Obturator externus
•Quadratus femoris

22. Hip lateral rotators
Lateral rotation occurs with every step to accommodate the
rotation of pelvis.

23. Movements at the Hip
Medial Rotation
•the tensor fasciae latae
(outer hip)
•parts of the gluteus medius and
the gluteus minimus (upper
buttocks)
•the adductor longus, brevis,
and magnus (inner thigh)
•the pectineus (upper frontal
thigh)

24. Medial Rotation
Medial rotation is not a resisted motion requiring a substantial
amount of force .
Medial rotators are weak as compare to lateral

25. Horizontal abd and adduction
H.Abd and H.add occurs when hip is in
flexion 90. while femur is either adducted or
abducted.
These actions require the simultaneous
coordinated actions of several muscles.
Tension is required in hip flexors for
elevation of femur then hip abd perform
H.abd and hip adductors do H.adduction.

26. Loads on Hip
In upright standing when BW is evenly distributed across
the legs , the W supported at each hip is 1/3 total BW.
Total load in this situation is greater than weight supported
because of tension in strong hip muscle add up
compression.
Gait speed increases , loads on hip increase
As Loading increases contact area increases such that
stress level remains constant approximately.
Major forces on hip during static stance are weight of body
segments above hip , tension in hip abductors and joint
reaction forces.

27. 238% of BW during support phase
251% in climbing
260 in descending stairs
4.2 to 8.6 times BW in side diving

28. COMMON INJURIES OF
THE HIP
Fractures
• Hip is subjected to high repetitive loads---4-7
times the body weight during locomotion
• Fractures of femoral neck(broken hip) occurs during support phase
among elderly people with osteoporosis(reduced bone min and strength).
• Loss of balance and fall can cause fracture………Common
misconception.
•Half of all femoral neck fractures can be attributed to osteoporosis.
•Regular physical activity protects against risk of hip fracture.

29. Injuries contd…
CONTUSIONS
•Anterior aspect muscles--- prime
location for direct injury in Contact
sports----Internal hemorrhaging---
Appearance of bruises mild to severe
Uncommon but serious complication
compartment syndrome---internal
hemorrhage--compression on nerves,
vessels, muscle----tissue death

30. Injuries contd…
STRAINS: injury to muscle tendon.
•Hamstring strain…….late stance or late swing
phase as ecentric contraction.(simultaneous hip flexion
&knee extension)
•Groin Strain….forceful thigh movement in abduction
causes strain in adductors(ice hockey players

31. KNEE BIOMECHANICS

32. Structure of the Knee
Modified hinge joint. Formed by
Tibofemoral & patello femoral joit
What is the tibiofemoral joint?
• dual condyloid articulations between
the medial and lateral condyles of
the tibia and the femur; composing
the main hinge joint of the knee
• considered to be the knee joint

33. Condyles of tibia== tibial plateaus
Screw home –locking mechanism
Open chain and closed chain
Close pack position= full extension
Open pack position= 25◦

34. Femur
Medial and lateral condyles
Convex, asymmetric
Medial larger than
lateral
34

35. Tibia
Medial tibial condyle: concave
Lateral tibial condyle: flat or concax
Medial 50% larger than lateral
1
35

36. Structure of the Knee
Bony structure of the tibiofemoral joint.
Patella
Tibia
Fibula
Femur

37. Structure of the Knee
• The menisci of the knee. Medial meniscus is also attached
directly to the medial collateral ligament
Lateral meniscus
Posterior cruciate ligament
Transverse ligament
Anterior cruciate ligament
Medial meniscus
Superior view

38. • Deepens the articulating depression of tibial
plateaus
• Load transmission and shock absorption
• If menisci are removed stress may reach
up to 3 times
• Increased likelihood of degenerative
conditions

39. Knee Ligaments:

40. Medial & lateral stabilizers
(mostly ligaments)
Ligaments
most important static stabilizers & dynamic
tensile strength - related to composition
Primary valgas restraint -57-78% restraining
moment of knee
Tense in lateral rotation, lax in flexion

41. Lateral side
LCL
Primary Varus restraint
lax in flexion

42. Cruciates
ACL
Primary static restraint to anterior displacement
tense in extension, ‘lax’ in flexion
PCL
Primary restraint to post. Displacement - 90%
relaxed in extension, tense in flexion
restraint to Varus/ valgus force
resists rotation, esp.int rot of tibia on femur

44. Structure of the Knee
What is the patellofemoral joint?
• articulation between the patella and
the femur
• (the patella improves the mechanical
advantage of the knee extensors by
as much as 50%)
•Movement at knee joint & muscles

45. Patellofemoral joint motion
Gliding movements== 7 cm in vertical
direction
Superior glide
Inferior glide
Lateral and medial shifting

46. Loads on the knee joint
Tibiofemoral joint:
Compression loading more in stance phase
Shear loading= tendency of the femur to
displace anteriorly on tibial plateaus(glide)
Knee flexion angle exceeding than 90
degree result in larger shear forces.
Full squats not recommended for novice
athletes

47. forces at Patellofemoral
joint
1/3rd of body weight compressive forces
during normal walking
3 times the body weight during stair
climbing--High compressive forces
during knee flexion
Squatting highly stressful to the knee
complex

48. Common Injuries of the Knee
& Lower Leg

49. Knee Anatomy

50. Patella Fractures
Result from direct blow such as knee
hitting dashboard in MVA, fall on
flexed knee, forceful contraction of
quad. Muscle.
Transverse fractures most common

51. Patella Fracture:

52. Femoral Condyle Fractures
These injuries secondary to direct trauma
from fall w/axial loading or blow to distal
femur.

53. Femoral Condyle Fracture:

54. Anterior Cruciate Ligament
a deceleration,
hyperextension or
internal rotation of
tibia on femur
May hear “pop”,
swelling, assoc.
w/medial meniscal
tear
Excessive anterior
translation or
rotation of femur on
the tibia

55. Incidence of ACL
injuries is more in
females
Notable lessening of
flexion extension
range of motion at the
knee due to
quadriceps avoiding
Altered joint
kinetics== subsequent
inset of osteoarthritis

56. Surgical repair through middle third of
patellar tendon
Notable weakness in quadriceps, impaired
joint range and proprioception
Muscle inhibition: inability to activate
all motor units of a muscle during
maximal voluntary contraction

57. Posterior Cruciate
Ligament
Less common than ACL
injury
Mechanism is hyperflexion
of knee with foot
plantarflexed
Impact with dash board
during motor vehicle
accident
Direct force on proximal
anterior tibia

58. Medial collateral ligament
injury
Blows to the lateral side more
common
Valgus stress
Contact sports= football=
MCL injury more common
Both MCL and LCL injured in
wrestling

60. Prophylactic knee bracing
To prevent knee ligament injuries in
contact sports
Matter of contention
Protection from torsional loads
Reduced sprinting speed and earlier onset
of fatigue

61. Meniscus Injuries
Mechanism is usually squatting or twisting
maneuvers.
There is locking of the knee on flexion or
extension that is painful or limits activity.
Medial meniscus more commonly
damaged due to its attachment with the
MCL
Combination injuries

62. Iliotibial band friction
syndrome
Friction of posterior edge of Iliotibial band
against the lateral condyle of the femur
during foot strike
Very common in distance runners, hence
referred as runner’s knee
Training errors and anatomical
malalignments
Excessive tibial lateral torsion, femoral
anteversion, genu valgum, genu varum,
increased Q angle etc,

63. Breaststroker's knee
Forceful whipping together of
the lower leg produces
propulsive thrust
Excessive abduction of the
knee
Irritation of the MCL and
medial border of the patella
Hip abduction less than 37 or
greater than 42 degree ==
increased onset of knee pain

64. Patellofemoral pain
syndrome
Painful Patellofemoral joint motion
involving anterior knee pain after activities
requiring repeated flexion at the knee
Anatomical malalignments
Vastus Medialis Oblique and Vastus
Lateralis in strength
Large Q angle responsible
Patellar maltracking

69. Chondromalacia Patellae
Overuse syndrome of patellar cartilage
Caused by patello-femoral malalignments
which leads to tracking abnormality of
patella putting excessive lateral pressure
on articular cartilage
Seen in young active women, pain worse
w/stair climbing and rising from a chair

70. Shin Splints
Generalized pain along the anterolateral
or posteromedial aspect of the lower leg is
commonly known as shin splints
Overuse injury often associated with
running, dancing on the hard surface and
running uphill

71. Structure of the Ankle
Tibiotalar joint
• Hinge joint where the convex surface of
the superior talus articulates with the
concave surface of the distal tibia
• considered to be the ankle joint

72. Structure of the Ankle
The bony structure of the ankle.
Fibula
Tibia
Talus
Calcaneus
Posterior view

73. Movements at the Ankle
Dorsiflexion at the ankle
• Tibialis anterior
• extensor digitorum longus
• peroneus tertius
• assisted by:
• extensor hallucis longus

74. Movements at the Ankle
plantar flexion at the ankle
• Gastrocnemius
• soleus
• assisted by:
Tibialis posterior, Plantaris, peroneus
longus, flexor hallucis longus,
peroneus brevis, flexor digitorum
longus

75. Structure of the Foot
Subtalar joint
(the anterior and posterior facets of the
talus articulate with the sustentaculum
tali on the superior calcaneus)

76. Structure of the Foot
tarsometatarsal and intermetatarsal joints
• Nonaxial joints that permit only gliding
movements
• Enable the foot to function as a semirigid unit
and to adapt flexibly to uneven surfaces during
weight bearing

77. Structure of the Foot
metatarsophalangeal and interphalangeal
joints
• Condyloid and hinge joints, respectively
• Toes function to smooth the weight shift to
the opposite foot during walking and help
maintain stability during weight bearing by
pressing against the ground when necessary

78. Structure of the Foot
plantar arches
• The medial and lateral longitudinal
arches stretch form the calcaneus to the
metatarsals and tarsals
• The transverse arch is formed by the
head of the metatarsal bones &
longitudinal by base of metatarsals

81. Structure of the Foot
Plantar Fascia
• Thick bands of fascia that cover the plantar
aspects of the foot
• During weight bearing= mechanical energy is
stored in the stretched ligaments, tendons, and
plantar fascia of the foot.
• This energy is released to assist with push-off
of the foot from the surface.

82. Structure of the Foot
The plantar fascia.
Lateral view
Plantar view
Plantar fascia

83. Movements of the Foot
Toe flexion and extension
• Flexion - flexor digitorum longus, flexor
digitorum brevis, lumbricals, Interossei
• Extension - extensor hallucis longus, extensor
digitorum longus, extensor digitorum brevis

84. Movements of the Foot
Inversion and eversion
• Inversion - Tibialis posterior, Tibialis anterior
• Eversion - peroneus longus, peroneus brevis,
assisted by peroneus tertius

85. Common injuries of the
ankle and foot
•Ankle injuries
•Inversion sprains= stretching or rupture of
lateral ligaments
•Medial = deltoid ligament very strong
•Ankle bracing or taping

89. OVERUSE INJURIES
•Achilles tendinitis
•Plantar fascitis
•Stress fractures
•Dancing en pointe
= stressed second
metatarsal

90. Alignment anomalies of the
foot
•Forefoot
Valgus
•Forefoot Varus
•Hallux Valgus
•Hallux Varus

91. Injuries related to high and low arch structures
High arches= increased incidence of ankle
sprains, plantar fascitis, ITB friction
syndrome, 5th metatarsal fracture
Low arches= knee pain, patellar tendinitis,
plantarfascitis,