Kinesiology of the Lower Limb-Knee Joint-Session 4

1. Structure and Function of the Knee
Presented by : Zinat Ashnagar, PT, PhD
Assistant Professor, Tehran University of Medical Sciences
https://orcid.org/0000-0001-5515-2130
Zinatashnagar@gmail.com
https://www.researchgate.net/profile/Zinat_Ashnagar

2. 2Kinesiology of the Lower Limb

3. 3Kinesiology of the Lower Limb

4. • In open chain, up to 20 to 30 degrees of medial,
or internal rotation, and 10 to 20 degrees of
adduction of the tibia on the femur occurs during
movement from full extension to 90 degrees of
flexion.
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5. • Conversely, movement from flexion to extension
involves 30 to 40 degrees of lateral, or external
rotation, and 10 to 20 degrees of abduction.
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6. PF joint alignment
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7. 7Kinesiology of the Lower Limb

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10. • Accessory patellar kinematics normally accompany all
knee motions and patellofemoral movements.
• Although not well understood or predictable, there is
likely an optimal amount and pattern of patellar
accessory kinematics that help minimize the stress
within the patellofemoral joint.
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11. 11Kinesiology of the Lower Limb

12. • Normal medial/lateral alignment of the patella
relative to the femur during motion, also referred
to as patellar medial/lateral tracking or glide, is
generally considered to reveal equidistance of
the patella relative to the femoral condyles.
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13. 13Kinesiology of the Lower Limb

14. Patellar tilt
• Describes the alignment of the patella about a
superior-inferior axis.
• In full extension, the patella is normally in a
small degree of lateral tilt.
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15. 15Kinesiology of the Lower Limb

16. Patella Alta and patella Baja
• Patella that is displaced superiorly and inferiorly,
respectively.
• Superior/inferior alignment of the patella
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21. Patellar medial and lateral rotations
• Determined by the inferior pole of the patella
about an anterior-posterior axis may also be
observed.
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22. 22Kinesiology of the Lower Limb

23. • Malalignment of the patella relative to the femur
in any direction may place abnormal stresses
through the PF joint or render the joint less
stable.
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24. • Mobility restrictions of the PF joint may limit the
overall motions of the knee.
• Superior and inferior gliding of the patella during
active knee extension and flexion is required for
normal TF extension and flexion, respectively.
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25. • Medial and lateral gliding of the patella is an
important component motion for medial and lateral
rotation of the tibia relative to the femur.
• In sitting, the clinician observes the C-curve path
as the knee moves from extension to flexion,
which reverses during movement from flexion to
extension.
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26. 26Kinesiology of the Lower Limb

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31. ROLE OF QUADRICEPS MUSCLE IN PATELLAR TRACKING
• As the knee is extending, the quadriceps muscle pulls the
patella superior, slightly lateral, and slightly posterior in
the intercondylar groove.
• Vastus lateralis has a larger cross sectional area and force
potential.
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32. • Activation of the quadriceps as a whole pulls and
compresses the patella posteriorly against the femur,
thereby stabilizing its of path of movement relative
to the distal femur.
• This stabilization effect increases with the knee in
greater flex.
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33. 33 Kinesiology of the Lower Limb

34. Even in full EXT, some fibers of the quadriceps are aligned
to produce a posterior compression through the PF joint.
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35. 35Kinesiology of the Lower Limb

36. • Although relatively small, the posterior stabilizing effect on
the patella is specially useful in the last 20 to 30 degrees of
EXT at a point when
• 1)the patella is no longer fully engaged whithin the trochlear
groove of the femur
• 2) the resultant PF joint compression (stabilizing) force
produced by the activated quadriceps as a whole is at least.
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37. 37Kinesiology of the Lower Limb

38. • The quadriceps angle (Q-angle) is a measure of the
lateral pull of the quadriceps.
• Q-angles average about 13 to 15 (±4.5) degrees.
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39. QUADRICEP
S PULL &
Q-ANGLE
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41. • A large Q-angle resulting from malalignment of
the hip or ankle creates a bow-stringing force
that naturally pulls the patella laterally on
activation of the quadriceps.
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42. LOCALLY PRODUCED FORCES ACTING ON THE PATELLA
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43. • activation of the quadriceps naturally produces a
lateral “bow-stringing force” on the patella that is
proportionate to the strength of the quadriceps
and the valgus alignment of the knee.
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44. LOCAL FACTORS THAT NATURALLY OPPOSE THE LATERAL
PULL OF THE QUADRICEPS ON THE PATELLA
– The lateral facet of the intercondylar groove is normally steeper than the
medial facet which blocks or resists the approaching patella.
– The oblique fibers of the vastus medialis balance the lateral
pull.
– Medial patellar retinacular fibers are oriented in medial-distal and medial
directions (referred to as the medial patellofemoral ligament). Often
ruptured after a complete lateral dislocation of the patella.
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45. 45Kinesiology of the Lower Limb

46. GLOBAL FACTORS
• Factors that resist excessive valgus or the extremes of axial
rotation of the tibiofemoral joint favor optimal tracking of the
patellofemoral joint.
• Excessive genu valgum can increase the Q-angle and thereby
increase the lateral bowstring force on the patella.
• Increased valgus can occur from laxity or injury to the MCL.
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47. Weak external rotators or abductors of the hip
• During gait or weight-bearing activities, a person
with weak hip external rotators and abductors
may have difficulty preventing the femur from
drifting into adduction and internal rotation.
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48. • With the foot securely planted, excessive internal
rotation and adduction of the femur (hip)
increase the genu valgum of the knee. As a
result, the patella is forced laterally.
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49. • Pronation of the foot can force the tibia medially,
thereby creating increased valgus of the knee.
• The greater the valgus position of the knee, the
greater the potential for lateral tracking of the
patella.
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50. 50Kinesiology of the Lower Limb

51. • Weakness of the hip abductors (coxa vara) can allow the
hip to slant excessively medial, which in turn places
excessive stress on the medial structures of the knee.
• Excessive internal rotation of the knee, which is related to
excessive pronation of the subtalar joint during walking.
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52. BOWSTRING FORCE ON THE PATELLA
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53. 53Kinesiology of the Lower Limb

54. CAUSES OF EXCESSIVE LATERAL TRACKING OF THE PATELLA
Structural of Functional Cause Specific Examples
Bony Dysplasia Dysplastic lateral facet of the intercondylar
groove of the femur (“shallow” groove)
Dysplastic or “high” patella (patella alta)
Excessive laxity in periarticular connective
tissue
Laxity of medial patellofemoral ligament
Laxity or attrition of medial collateral ligament
Laxity or reduced height of the medial
longitudinal arch of the foot (overpronation of
the subtalar joint)
Excessive stiffness or tightness in
periarticular connective tissue and muscle
Increased tightness in the lateral patellar
retinacular fibers or iliotibial band
Increased tightness of the internal rotator or
adductor muscles of the hip54 Kinesiology of the Lower Limb

55. Structural of Functional Cause Specific Examples
Extremes of bony or joint alignment Coxa varus
Excessive anteversion of the femur
External tibial torsion
Large Q-angle
Excessive genu vlagum
Muscle weakness Weakness or poor control of
•Hip external rotator and abductor muscles
•The vastus medialis (oblique fibers)
•The tibialis posterior muscle (related to
overpronation of the foot)
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56. KNEE FLEXOR-ROTATOR MUSCLES
With the exception of the gastrocnemius, all muscles
that cross posterior to the knee have the ability to flex
and to internally or externally rotate the knee.
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57. Flexor-rotator group
– Hamstring
– Sartorius
– Gracilis
– Popliteus
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58. The flexor-rotator group has three sources of
innervation
– Femoral
– Obturator
– Sciatic
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59. KNEE FLEXOR-ROTATOR MUSCLES: FUNCTIONAL ANATOMY
• The hamstring muscles have their proximal attachment
on the ischial tuberosity (with the exception of the short head of biceps).
• The hamstrings extend the hip and flex the knee.
• In addition to flexing the knee, the medial hamstrings
(semimembranosus and semitendanosus) internally
rotate the knee.
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60. 60Kinesiology of the Lower Limb

61. KNEE FLEXOR-ROTATOR MUSCLES: GROUP ACTION
• The biceps femoris flexes and externally rotates the
knee.
• The sartorius, gracilis, and semitendinosus attach to the
tibia using a common, broad sheet of connective tissue
known as the pes anserinus.
• The “pes muscles” are internal rotators of the knee.
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62. POPLITEUS MUSCLE “KEY TO THE KNEE”
• The popliteus muscle is an important internal rotator
and flexor of the knee joint.
• As the extended and locked knee prepares to flex, the
popliteus provides an important internal rotation torque
that helps to mechanically unlock the knee.
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63. 63Kinesiology of the Lower Limb

64. • The popliteus has an oblique line of pull.
• This muscle has the most favorable leverage of all of
the knee flexor muscles to produce a horizontal plane
rotation torque on an extended knee.
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65. • The average axial rotation leverage for all rotators of the
knee is greatest between 70 to 90 degrees of knee
flexion.
• The only exception is the popliteus muscle, which has is
greatest moment arm to internally rotate the knee at
about 40 degrees of knee flexion.
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66. 66Kinesiology of the Lower Limb

67. CONTROL OF TIBIAL-ON-FEMORAL OSTEOKINEMATICS
An important action of the flexor-rotator muscles is to
accelerate or decelerate the lower leg during the swing
phase of walking or running.
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68. • Typically, these muscles produce relatively low to
moderate forces but at relatively high shortening or
lengthening velocities.
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69. • Through eccentric action, the muscles help to dampen
the impact of full knee extension.
• They shorten the functional length of the lower limb
during the swing phase.
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70. 70Kinesiology of the Lower Limb

71. CONTROL OF FEMORAL-ON-TIBIAL OSTEOKINEMATICS
The muscular demand needed to control femoral-on-
tibial motions is generally larger and more complex than
that needed for most tibial-on-femoral knee motions.
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72. • The sartorius may have to simultaneously control up to
five degrees of freedom (i.e. two at the knee and three
at the hip).
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75. KNEE AS A PIVOT POINT – AXIAL ROTATION
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76. The pes anserinus group may be regarded as a
“dynamic medial collateral ligament” by resisting
not only the external rotation of the knee but also
any valgus loads.
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77. Maximal Torque Production of the Knee Flexor-Rotator
Muscles
Maximal-effort flexion torque is generally greatest with
the knee in the last 20 degrees of full extension and then
declines steadily as the knee is progressively flexed.
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78. 78Kinesiology of the Lower Limb

79. The hamstrings have their greatest flexor moment arm
(leverage) at 50 to 90 degrees of knee flexion.
The hamstrings (and other knee flexors) generate their
greatest torque at knee angles that coincide with relative
elongated muscle length, rather than high leverage.
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81. • Flexing the hip to elongate the hamstrings promotes
even greater knee flexion torque.
• The length-tension relationship appears to be a very
influential factor in determining the flexion torque
potential of the hamstring muscles.
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82. ABNORMAL ALIGNMENT OF THE KNEE: FRONTAL PLANE
• In the frontal plane the knee is normally aligned in about
5 to 10 degrees of valgus.
• Deviation from this alignment is referred to as excessive
genu valgum or genu varum.
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83. 83Kinesiology of the Lower Limb

84. GENU VARUM WITH UNICOMPARTMENTAL
OSTEOARTHRITIS OF THE KNEE
• During walking across level terrain, the joint reaction force
at the knee is about 2.5 to 3 times body weight.
• The force is created primarily by interaction of the forces
generated by muscles throughout the lower limb and by the
ground reaction force.
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85. 85Kinesiology of the Lower Limb

86. • The ground reaction force passes just lateral to the
heel, then upward to the medial knee.
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87. • By passing medial to an anterior-posterior axis at the
knee, the ground reaction force produces a varus torque
with each step.
• As a result, joint reaction force during walking is
normally several times greater on the medial joint
compartment than the lateral compartment.
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88. Throughout one’s lifetime, this repetitive varus loading is
partially absorbed by tension in structures, including the
lateral collateral ligament and iliotibial band.
Most persons tolerate the asymmetric dynamic loading of
the knee with little or no difficulty.
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89. In some individuals this asymmetric dynamic loading can
lead to excessive wear of the articular cartilage and
ultimately to medial unicompartmental osteoarthritis.
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90. 90Kinesiology of the Lower Limb

91. GENU VARUM
(BOW-LEG)
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92. • Thinning of the articular cartilage on the medial
side can tilt the knee into genu varum, or a bow-
legged deformity.
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93. • This deformity can initiate a vicious cycle:
the varus deformity increases medial joint
compartment loading, resulting in greater loss of
medial joint space, greater knee adduction
movement, increased strain on the lateral
collateral ligament, further increased medial
joint loading and so on.
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94. • In addition to surgery, other more conservative
measures have been found to reduce contact forces on
the medial side of the knee in persons with medial
compartment osteoarthritis including:
Strengthening of Gmax and tensor fascia lata and wearing
lateral wedge insoles.
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96. GENU VARUM (BOW-LEG) / HIGH TIBIAL OSTEOTOMY
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97. EXCESSIVE GENU VALGUM
• Several factors can lead to excessive genu valgum or
knock-knee.
• Previous injury, genetic predisposition, high body mass
index, and laxity of ligaments.
• Coxa vara or weak hip abductors can lead to genu
valgum.
• Excessive foot pronation
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98. GENU VALGUM
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100. • Over time, the tensional stress placed on the MCL and
adjacent capsule may weaken the tissue.
• Excessive valgus of the knee may negatively affect
patellofemoral joint tracking and create additional stress
on the ACL.
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101. • Standing with a valgus deformity of approximately 10
degrees greater than normal directs most of the joint
compression force to the lateral joint compartment.
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102. • This increased regional stress may lead to lateral
unicompartmental osteoarthritis and has been shown
to occur more often in women.
• Knee replacement surgery may be indicated to correct a
valgus deformity, especially if it is progressive, is painful,
or causes loss of function.
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103. 103Kinesiology of the Lower Limb

104. SAGITTAL PLANE: GENU RECURVATUM
• Full extension with slight external rotation is the knee’s
close-packed, most stable position.
• The knee may be extended beyond neutral an
additional 5 to 10 degrees.
• Hyperextension beyond 10 degrees of neutral is called
genu recurvatum
(Latin genu, knee, + recurvare, to bend backward).
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105. Standing with the knee in full extension usually directs the
line of gravity from body weight slightly anterior to the
medial-lateral axis of rotation at the knee.
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106. Genu recurvatum
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107. Gravity, produces a slight knee extension torque that can
naturally assist with locking of the knee, allowing the
quadriceps to relax intermittently during standing.
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108. Normally, this gravity-assisted extension torque is resisted
primarily by passive tension in the stretched posterior
capsule and stretched flexor muscles of the knee,
including the gastrocnemius.
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109. • Chronic, overpowering (net) knee extensor torque
eventually overstretches the posterior structures of the
knee.
• Due to poor postural control or neuromuscular disease
(i.e. polio).
• That causes spasticity and / or paralysis of the knee
flexors.
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110. 110 Kinesiology of the Lower Limb

111. Most functional activities of the lower extremity
combine the motions of:
(1) Hip flexion and knee flexion
(2) Hip extension and knee extension.
• Consider these motions while jumping or climbing
up a steep hill, for example.
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112. • These movements are not random but
occur naturally to help the rectus femoris
and the hamstrings remain close to their
optimal length for producing effective
forces.
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113. 113Kinesiology of the Lower Limb

114. • Consider the simultaneous action of hip extension
and knee extension, a natural motion used during
running.
• The semitendinosus, for example, actively shortens
to extend the hip;
• At the same time, this muscle is passively stretched
as the knee is actively extended by the quadriceps.
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115. As the active rectus femoris extends the knee, it is
simultaneously stretched across the extending hip.
Therefore, during combined hip and knee extension, both
the rectus femoris and the semitendinosus muscle
avoid over-contracting (shortening) across the hip and
knee.
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116. If this were to happen, the muscles would rapidly become
actively insufficient and unable to generate effective forces.
Consider, for example, the consequence of trying to
combine active hip extension with knee flexion.
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117. 117Kinesiology of the Lower Limb

118. During this seemingly unnatural motion, the
hamstring muscles actively and quickly over-
shorten across the hip and knee at once—a
situation that significantly reduces their force-
producing potential.
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119. Furthermore, the over-stretched rectus femoris
becomes passively insufficient, thereby further
limiting the ability of the hamstrings to flex the knee
and extend the hip.
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120. 120Kinesiology of the Lower Limb

121. 121Kinesiology of the Lower Limb

122. References
• Mansfield PJ, Neumann DA. Essentials of Kinesiology for the Physical
Therapist Assistant E-Book. Elsevier Health Sciences; 2018 Oct 23.
• Neumann DA. Kinesiology of the musculoskeletal system; Foundation for
rehabilitation. Mosby & Elsevier. 2010.
• Wise CH. Orthopaedic manual physical therapy from art to evidence. FA
Davis; 2015 Apr 10.
• https://vdocuments.mx/kinesiology-of-the-musculoskeletal-system-dr-michael-p-
gillespie.html
• PPT "KINESIOLOGY OF THE MUSCULOSKELETAL SYSTEM Dr. Michael P. Gillespie."
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123. ThanksforYourAttention
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