Biomechanics of knee joint.dbbdndxbwjdjrjrjr

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1. KNEE JOINT
BIOMECHANICS
By: Dr.SnehaKumbhani(M P T in musculoskeletal)

2. Knee complex
The knee complex is one of the most
often injured joints in the human
body.
The numerous ligamentsalong with
numerous musclescrossing the joint
provides more joint complexity.
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3. This anatomical complexity is
necessary for stability and mobility
roles.
Knee joint works in conjunction with
the hip and ankle joint to support the
body’s weight during static erect
posture.
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4. Dynamically it is responsible for
moving and supporting the body
during both routine and difficult
activities.
So, it is responsible for major
stability and major mobility roles.
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5. INTRODUCTION
The knee complex is composed of two distinct
articulations located within a single joint capsule.
TibiofemoralJoint
Patellofemoral joint
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6. Tibiofemoraljoint
Articulation between distal femur
and proximal surface of tibia.
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7. Patellofemoral joint
Articulation between posterior part
of patella and femur.
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8. KNEE JOINT -BIOMECHANICS
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9. Double-condyloidjoint
3 degrees of freedom
Flexion & extension
Medial & lateral rotation
Abduction & adduction(valgus &
varusof the knee)
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9 TIBIO-FEMORAL JOINT

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11. FEMUR
The proximal articular surface -The large
medial & lateral condyles of the femur.
Because of the obliquity of the shaft of
the femur, the femoral condyles do not lie
immediately below the femoral head but
are slightly medial to it.
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12. KNEE JOINT -BIOMECHANICS
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13. In the sagittal plane, the condyles have a
convex shape, with a smaller radius of
curvature posteriorly.
The 2 condyles are separated inferiorly by
the intercondylar notch but are joined
anteriorly by an asymmetrical, shallow
groove called the patellar groove.
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14. TIBIA
The asymmetrical medial & lateral tibialcondyles
or plateaus.
The medial tibialplateau is larger in the antero-
posterior direction than the lateral plateau.
The tibialcondyles are separated by a
roughened area & two bony spines called the
intercondylar tubercles.
These tubercles become lodged in intercondylar
notch of the femur during knee extension.
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16. KNEE JOINT -BIOMECHANICS
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17. The tibialplateaus are
predominantly flat and does not
match up well with the convexity
of the femoral condyles.
Because of this lack of bony
stability, accessory joint structures
(menisci) are necessary to improve
joint congruency.
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18. Hip joint
Knee joint
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19. Meniscus
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20. TIBIO-FEMORAL
ALIGNMENT
The anatomic (longitudinal) axis of the femur
is oblique, directed inferiorly and medially
from its proximal to distal end.
The anatomic axis of the tibia is directed
almost vertically.
Angle 180 to 185 degree -creating a slight
physiologic valgus angle at the knee.
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21. TIBIO-FEMORAL ALIGNMENT
Angle >185 degree -GENU VALGUM (knock knees).
Angle <75 degree -GENU VARUM (bow legs) exists.
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22. TIBIO-FEMORAL ALIGNMENT
An alternative method of measuring tibio-
femoral alignment is performed by drawing a
line from the center of the femoral head to the
center of the head of talus.
This line represents the mechanical axis or
weight bearing line of the LE, and in a normally
aligned knee, it will pass through the center of
the joint between the intercondylartubercles.
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23. WEIGHT-BEARING FORCES:
In bilateral stance, the weight bearing
stresses on the knee joint are equally
distributed between medial and lateral
condyles.
In unilateral stance, compartmental
loading is altered, i.e. the weight
bearing line must shift medially across
knee joint.
Genu varummay contribute to the
progression of medial compartment
knee OA.
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24. TIBIO-FEMORAL ALIGNMENT
& WEIGHT-BEARING FORCES:
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25. MENISCI:
Tibiofemoralcongruence is improved by the medial
and lateral menisci, forming concavities in to which
the femoral condyles sit.
Functions of Menisci include:
Improve joint congruence.
Distribute weight bearing forces.
Reduce friction between tibia & femur.
Serve as shock absorbers.
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26. MENISCI:
Fibro-cartilaginous disks
Semicircular shape.
Medial meniscus is C-
shaped
Lateral meniscus forms
4/5 of a circle.
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27. MENISCAL
ATTACHMENTS:
The open anterior and posterior ends of menisci are
called anterior and posterior horns & are firmly attached
to the tibia below.
The medial meniscus has greater ligamentous and
capsular restraints than does the lateral meniscus and this
relative lack of mobility may contribute to its greater
incidence of injury.
Anteriorly the menisci are connected to each other by
the transverse ligament.
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28. Both menisci are also attached directly or indirectly to
the patella via the patellomeniscalligaments.
At the periphery, the menisci are connected to the
tibialcondyle by the coronary ligaments.
The anterior and posterior horns of the medial
meniscus are attached to
ACL
PCL
semimembranosus muscle.
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29. The tendon of the popliteusmuscle attaches to the
lateral meniscus which helps to restrain or control the
motion of the lateral meniscus.
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30. MENISCAL NUTRITION
AND INNERVATION:
During 1st year of life, the meniscus contains blood vessels
through out the meniscal body.
Once weight bearing is initiated, vascularity begins to
diminish until only the outer 25% to 33% is vascularized by
capillaries from the joint capsule and the synovial
membrane.
After 50 years of age, only the periphery of the meniscal
body is vascularized.
Therefore the peripheral portion obtains its nutrition
through blood vessels, but the central portion must rely on
the diffusion of synovial fluid & this requires intermittent
loading of meniscus by either weight bearing or muscular
contractions.
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31. MENISCAL NUTRITION
AND INNERVATION:
The horns of the menisci and the peripheral
vascularized portion of the meniscal bodies are well
innervated with the free nerve endings (nociceptors)
& three different mechanoreceptors (Ruffini
corpuscles, pacinian corpuscles and GTO).
The presence of nociceptors could explain some of
the pain felt by patients after a meniscal tear.
Proprioceptive deficits may potentially occur after
meniscal injury as a result of injury to the
mechanoreceptors with in the meniscus.
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32. JOINT CAPSULE:
The joint capsule that encloses the tibio-
femoral & patello-femoral joints is large &
lax.
It is grossly composed of exterior or
superficial fibrous layer and a thinner
internal synovial membrane.
The fibrous portion of the capsule is firmly
attached to the inferior aspect of the femur
& superior portion of the tibia.
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33. JOINT CAPSULE:
The patella, tendon of
quadriceps & the patellar
tendon complete the anterior
portion of the capsule.
The antero-medial & antero-
lateral portions of the capsule
are often separately identified
as the medial & lateral patellar
retinaculae, or together as
extensor retinaculum.
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35. JOINT CAPSULE:
The joint capsule is strongly innervated by
both nociceptorsas well as pacinian&
Ruffinicorpuscles.
The joint capsule is responsible for
providing a tight seal for keeping the
lubricating synovial fluid within the joint
space.
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36. EXTENSOR RETINACULUM:
The medial & lateral retinacula are composed of a
series of transverse and longitudinal bands that
connect the patella to surrounding structures.
These are:
Medial & lateral patello-femoral ligaments.
Medial & lateral patello-tibialligaments.
Medial patello-meniscal ligament.
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37. LIGAMENTS
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38. LIGAMENTS:
Medial Collateral Ligament
Lateral Collateral Ligament
Anterior Cruciate Ligament
Posterior Cruciate Ligament
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39. MEDIAL COLLATERAL
LIGAMENT:
Divided into superficial & deep portion separated by a bursa.
The superficial
from the medial femoral epicondyle to the medial aspect of the
proximal tibia.
The deep portion
From the medial femoral condyle to the medial tibialcondyle.
Rigidly affixed to the medial border of the medial meniscus.
Function
Primary restraint to excessive abduction (valgus) & lateral rotation
stresses at the knee.
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40. LATERAL
COLLATERAL
LIGAMENT:
The LCL -from the lateral femoral condyle to the
fibular head, where it joins with the tendon of the
biceps femorismuscle to form the conjoined tendon.
Function:
Check varusstresses at full extension.
Its orientation enables the LCL to limit excessive lateral
rotation of the tibia as well.
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41. ANTERIOR CRUCIATE
LIGAMENT:
FROM the anterior tibialspine and extends
posteriorly, laterally and superiorly to attach
to the postero-medial aspect of lateral
femoral condyle.
The ACL consist of two separate bands that
wrap around each other and are named for
their origins on tibia. These are:
Anteromedialband (AMB)
Posterolateralband (PLB)
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42. Function :
Primary restraint against anterior translation of the tibia on the femur.
This role belongs to either AMB or PLB, depending on the knee flexion
angle.
With the knee in full extension, the PLB is taut; as the knee flexion
increases, the PLB loosens and AMB becomes tight. This shift in tension
between the bands allows some portion of the ACL to remain tight at
all times.
In the intact joint, forces producing an anterior translation of tibia will
result in maximum excursion at 30 degrees of flexion when neither of
the ACL bands are particularly tensed.
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43. The ACL is also responsible for resisting hyperextension of the
knee.
ACL acts as a secondary restraint to either varusor valgus at
the knee.
Injury to ACL occurs most commonly when the knee is slightly
flexed & tibia is rotated in either direction in weight bearing.
In flexion & medial rotation, the ACL is tensed as it winds
around the PCL. In flexion & lateral rotation, the ACL is tensed
as it is stretched over the lateral femoral condyle.
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44. With the tibio-femoral joint in nearly full extension, a
quadriceps muscle is capable of generating an
anterior shear force on the tibia thereby increasing the
strain on ACL.
The gastrocnemius muscle has the potential to
translate the tibia anteriorly and strain the ACL,
because its proximal tendon wraps around the
posterior tibia, effectively pushing the tibia forward
when the muscle becomes tense through active
contraction or passive stretch.
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45. ANTERIOR CRUCIATE
LIGAMENT:
The hamstring muscles are capable of inducing a
posterior shear force on the tibia through out the range of
knee flexion, becoming more effective at greater knee
flexion angles. Therefore it relieves some of the stress of
the ACL.
With the foot on the ground, the soleus muscle may also
have the ability to posteriorly translate the tibia and assist
the ACL in restraining anterior tibialtranslation.
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46. POSTERIOR
CRUCIATE
LIGAMENT:
From to the posterior tibialspine & to the lateral aspect of the
medial femoral condyle.
The PCL is divided into an AMB & a PLB that are named for
their tibialorigins.
When the knee is close to full extension, the PLB becomes
taut & at 80 to 90 degrees of flexion, AMB is maximally taut
and the PLB is relaxed.
The PCL serves as the primary restraint to posterior
displacement, of the tibia beneath the femur.
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47. Function:
Restraining motion with knee flexed.
Secondary role in restraining varus& valgus stresses at the knee.
The popliteusmuscle shares the role of the PCL in resisting
posteriorly directed forces on the tibia & can contribute to
knee stability when the PCL is absent.
An isolated hamstring contraction might destabilize the knee
joint in the absence of the PCL (posterior shear force).
Quadriceps contraction reduces the strain in the PCL at knee
flexion angles between 20 and 60 degrees.
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48. Meniscofemoral ligament
Meniscofemoral ligament are not true ligament because
they attach bone to meniscus, rather than bone to bone.
however both originates from the posterior horn of the lateral
meniscus and insert over the lateral aspect of medial femoral
condyle either anteriot to PCL (ligament of humphry) or
posterior to PCL ( Ligament of wrisberg).
In a review of literature, Gupte and colleagues reported that
at least one of the meniscofemoral ligament are present in
91% of knees, with approximately 30 % of knees having both
the meniscofemoral ligaments.
⚫They may assist the PCL in restraining the posterior translation
of the tibia on femur.
⚫MFL can also assist the popliteus muscle by checking tibial
lateral rotation.
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49. LIGAMENTS OF THE
POSTERIOR CAPSULE:
Several structures reinforce the “corners” of the posterior
knee joint capsule.
Postero-medial -by the semimembranosus, by its tendinous
expansion called the oblique popliteal ligament
Postero-lateral corner -by the arcuateligament, the LCL,
iliotibial band, posterolateral part of joint capsule and the
popliteusmuscle and tendon.a
The arcuate ligament is a Y shaped capsular thickening
found in nearly 70% of knees.
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50. Both the posterior oblique ligament and the arcuate
ligaments are taught in full extension and assist in
checking hyperextension of the knee.
they also checks valgus and varus forces respectively.
after trauma of PCL and MCL, The POL and
posteromedial capsule become immediately
important stabilizers against posterior tibial translation.
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51. ILIOTIBIAL BAND:
The IT band or IT tract is formed proximally from
the fascia investing the tensor fascia lata, the
gluteus maximus& the gluteus mediusmuscle,
and inserts distally into the anterolateral tibia
(Gerdy’stubercle), reinforcing the anterolateral
aspect of the knee joint.
With the knee in flexion, the combination of the
IT band, the LCL, & the popliteal tendon
increases the stability of the lateral side of the
joint.
It also assist ACL in resisting anterior
displacement of the tibia on the femur.
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52. Bursae
The extensive array of ligaments and muscle crossing
the tibiofemoral joint, in combination with the large
excursion of bony segments, sets up the potential for
substantial frictional forces among muscular ,
ligamentous and bony structures.
numerous bursae however limits or prevwnts such
degenerative forces.
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53. BURSAE:
Three of the following bursaeare not seperate entities but areeither
extension of the capsule’s synoviumor communicate with synovial
lining of the joint capsule through small openings. They are:
The suprapatellarbursa
The subpoplitealbursa
The gastrocnemius bursa
In flexion the suprapatellarbursa is compressed anteriorly
In extension the subpopliteal& gastrocnemius bursa are compressed.
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54. BURSAE:
Other bursaeSare:
The prepatellarbursa
The infrapatellarbursa
The deep infrapatellarbursa.
These bursaebecome inflamed either
through direct injury to the knee or
through prolong repeated activities.
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55. TIBIO-FEMORAL
JOINT
FUNCTION
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56. JOINT KINEMATICS:
The primary angular motion
Flexion/extension
Medial/lateral (internal/external) rotation
Varus/valgus (adduction/abduction) motions can also occur
to a lesser extent.
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57. FLEXION/
EXTENSION:
The axis for tibio-femoral flexion and extension is a
horizontal line passing through the femoral epicondyles.
The initiation of knee flexion (0 –25 degrees) occurs
primarily as rolling.
As flexion continues, -simultaneous anterior glide
Extension of the knee from flexion is essentially a reversal
of this motion. i.e. initially anterior rolling –then glide
posteriorly just enough to create a pure spin of femur.
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58. When the tibia is flexing on fixed femur, the tibia both
rolls and glides posteriorly on the relatively fixed
femoral condyles.
Extension of the tibia on fixed femur incorporates an
anterior roll and glide of the tibialplateau on the fixed
femur.
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59. MENISCI IN
FLEXION/EXTENSION:
As extension continues, the anterior margins of the
menisci deform anteriorly with the femoral condyles.
The posterior deformation of the menisci is assisted by
muscular mechanisms to ensure that appropriate
meniscal motion occurs.
During knee flexion, the semimembranosus exerts a pull
on the medial meniscus, where as the popliteusassists
with the deformation of the lateral meniscus.
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60. KNEE JOINT -BIOMECHANICS
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61. FLEXION/EXTENSION R.O.M.
Passive range of knee joint flexion is generally considered
to be 130 –140 degrees.
During squatting ROM may reach 160 degree.
Normal gait on level ground requires approx 60 –70 degrees
knee flexion.
Ascending stairs requires about 80 degrees.
Sitting down into & rising from a chair requires 90 degrees
flexion or more.
Knee joint extension (hyper-extension) up to 5 degree is
considered normal.
Excessive knee hyper-extension (>5 degree) is termed
GENU RECURVATUM.
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62. Many of the muscles acting at the knee are twojoint
muscles crossing not only the knee but also the hip or
ankle.
Therefore, the hip joint’s position can influence the
knee joint’s ROM.
Passive insufficiency of the rectus femoriscould limit
knee flexion to 120 or less if the hip joint is
simultaneously hyperextended.
When the lower extremity is in weight-bearing, ROM
limitations at other joints such as the ankle may cause
restrictions in knee flexion or extension.
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63. With the ankle fixed in dorsiflexionby
the ski boot, the knee cannot be fully extended
without the forefoot’s
being lifted from the ground.
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64. With a fixed plantarflexiondeformity
of the ankle/foot, the knee is forced into hyperextension when
the foot is flat on the ground.
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65. Ski boots generally hold the ankle in dorsiflexion,
preventing full knee extension when the foot is on the
ground.
The choice is either to walk with flexed knees or to
walk on the heels.
The same problem may be created by a fixed
dorsiflexiondeformity in the ankle/foot complex.
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66. The opposite situation happens with a limitation in
dorsiflexion.
A limitation to ankle dorsiflexion(e.g., caused by tight
plantarflexors) may limit the amount of knee flexion
that can be performed without lifting the heel off the
ground.
If there is a fixed plantarflexiondeformity at the ankle,
the inability to bring the tibia forward in weight-
bearing may result in a hyperextension deformity
(genurecurvatum) at the knee.
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67. The relationship between ankle and knee motions
when the foot is on the ground can be exploited by
intentionally altering ankle joint motion (e.g., through a
heel lift or an ankle-foot orthosis) to prevent or control
undesired knee motions.
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68. MEDIAL / LATERAL
ROTATION:
Medial & lateral rotation of the knee joint are angular
motions that are named for the motion ( or relative
motion) of the tibia on the femur.
About a longitudinal axis that runs through or close to
medial tibialintercondylartubercle.
Consequently the medial condyle acts as the pivot
point while the lateral condyle moves through a
greater arc of motion, regardless of the direction of
motion.
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70. As the tibia laterally rotates on the femur, the medial
condyle moves only slightly anteriorly, where as the
lateral condyle moves a larger distance posteriorly, on
the relatively fixed femoral condyles.
During tibial medial rotation, medial condyle moves
slightly posterior & lateral condyle moves anteriorly
through a large arc of motion.
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71. During both medial & lateral rotation, the menisci will
distort in the direction of movement of the
corresponding femoral condyle, as they did in flexion
& extension.
Example: As the tibia medially rotates (femur laterally),
the medial meniscus will distort anteriorly & the lateral
meniscus will distort posteriorly.
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72. Axial rotation is permitted by articularincongruence and
ligamentouslaxity.
Therefore, the range of knee joint rotation depends on
the flexion/extension position of the knee.
When the knee is in full extension, the ligaments are taut,
the tibialtubercles are lodged in the intercondylarnotch,
and the menisci are tightly interposed between the
articulating surfaces; consequently, very little axial
rotation is possible.
As the knee flexes toward 90, capsular and ligamentous
laxity increase, the tibialtubercles are no longer in the
intercondylarnotch, and the condylesof the tibia and
femur are free to move on each other.
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73. As the knee flexes to 90 degrees, the condyles of the
femur & tibia are free to move over each other.
The maximum range of axial rotation is available at 90
degrees of knee flexion. The total medial & lateral
rotation is 35 degrees, with the range of lateral rotation
being slightly greater (0 to 20) than the range of medial
rotation (0 to 15).
The magnitude of axial rotation diminishes as the knee
approaches both full extension & full flexion.
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74. VALGUS (ABDUCTION) /
VARUS(ADDUCTION)
Frontal plane motion at the knee, although minimal,
does exist & contribute to normal functioning of the
tibio-femoral joint.
Frontal plane ROM is typically only 8 degrees at full
extension, and 13 degrees with 20 degrees of knee
flexion.
Excessive frontal plane motion could indicate
ligament insufficiency.
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75. There is evidence that the muscles that cross the knee
joint have the ability both to generate and control
substantial valgusand varustorques.
When there is ligamentouslaxity, the excessive
varus/valgusmotion or increased dynamic activity of
muscles attempting to control this excessive motion
could precipitate greater peak stresses across the
joint.
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76. COUPLED MOTIONS:
Typical tibio-femoral motions are not straight forward.
Infact, bi-planar intra-articular motions can occur
because of the oblique orientation of the axes of
motion with respect to the bony levers.
The true flexion/extension axis is not perpendicular to
the shaft of the femur & tibia. Therefore flexion &
extension do not occur as plane sagittal plane
motions but include frontal plane components termed
“coupled motions”.
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77. With knee flexion around oblique axis, the tibia moves
from a position oriented slightly lateral to the femur to
a position slightly medial to the femur in full flexion;
that is, the foot approaches to the midline of the
body.
Flexion is considered to be coupled to a varusmotion,
while extension is coupled with a valgus motion.
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78. AUTOMATIC OR LOCKING
MECHANISM OF THE KNEE:
Obligatory lateral rotation of the tibia that accompanies the
final stages of knee extension. This coupled motion (lateral
rotation with extension) is referred to as automatic or terminal
rotation.
During the last 30 degrees of knee extension, the shorter
lateral tibialplateau/femoral condyle pair completes its
rolling-gliding motion before the larger medial articular
surfaces do. As extension continues (in NWB motion of tibia),
the longer medial plateau continues to roll & glide anteriorly
after the lateral side of the plateau has halted.
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79. This continued anterior motion of the medial tibial
condyle results in the lateral rotation of the tibia on the
femur, with motion most evident in final 5 degrees of
extension. This is also known as the locking or screw home
mechanism.
To initiate knee flexion, the knee first must be unlocked;
that is laterally rotated tibia must medially rotate
concomitantly as flexion is initiated.
A flexion force will automatically result in medial rotation
of the tibia, because the longer medial side will move
before the shorter lateral compartment.
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80. This automatic rotation occurs in both WB & NWB knee
joint function.
In WB, the freely moving femur medially rotates on the
relatively fixed tibia during the last 30 degrees of knee
extension.
Unlocking consequently, is brought about by lateral
rotation of the femur on the tibia before flexion can
proceed.
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81. MUSCLES
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82. KNEE FLEXOR GROUP:
There are 7 muscles that flex the knee. These are:
Semimembranosus (SM)
Semitendinosus (ST)
Biceps femoris (long & short heads) (BF)
Sartorius (SRT)
Gracilis (GRL)
Popliteus (PPL)
Gastrocnemius (GNM)
Plantaris (frequently absent)
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83. All of the flexors are two joint muscles, with exception
of the short head of BF & PPL.
Five of the flexors medially rotate the tibia (PPL, GRL,
SRT, SM & ST) on a fixed femur, whereas the BF laterally
rotates the tibia.
The lateral muscles (BF, LGNM & PPL) produce valgus
moments, whereas those on the medial side (SM, ST,
MGNM, SRT & GRL) can generate varusmoments.
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84. The hamstring muscles -cross both the hip (as extensors) &
the knee (as flexors)
Greater hamstring force is produced with the hip in flexion
when the hamstrings are lengthened over that joint,
regardless of knee position.
In NWB activities, the hamstring generate a posterior shearing
force of the tibia on the femur that increases as the knee
flexion increases, peaking between 75 –90 degrees of knee
flexion. This can reduce strain on ACL, although increasing
strain on PCL.
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85. The 3 muscles of the pesanserinus(ST, SRT, GRL) appear
to function effectively as a group to resist valgus forces &
provide dynamic stability to the antero-medial aspect of
the knee joint.
Unlocking of the knee is attributed to the PPL, as it is a
medial rotator of the tibia on the femur.
Activity of both the SM & PPL, contribute to the posterior
movement & deformation of their respective menisci on
the tibialplateau.
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86. KNEE EXTENSOR GROUP:
The four extensors of the knee are collectively known
as the quadriceps femoris muscle. They are:
Vastus intermedius (VI)
Vastus lateralis (VL)
Vastus medialis (VM)
Rectus femoris (RF)
The RF is the only portion of quadriceps that crosses
both the hip & knee joints.
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87. PATELLAR INFLUENCE ON
QUADRICEPS FUNCTION:
Function of the quadriceps is strongly influenced by the
patella.
From the perspective of mechanical efficiency, the patella
lengthens the MA of the quadriceps by increasing the
distance of the quadriceps tendon & patellar tendon from
the axis of the knee joint.
The patella, as an anatomic pulley, deflects the action line of
the quadriceps away from the joint center, increasing the
angle of pull & the ability of the muscle to generate an
extension torque.
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88. In full knee flexion, patella is fixed firmly in
intercondylarnotch, which effectively eliminates the
patella as a pulley.
During subsequent knee extension, the MA of the
quadriceps lengthens as the patella leaves the
intercondylargroove & travels up the femoral
condyles.
Peak torques are at approx45 –60 degrees of knee
flexion.
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89. Increasing the quadriceps’ MA, also creates an anterior
shear of the tibia on the femur. This increases strain on
ACL.
In the absence of passive stabilizers such as ACL, a
quadriceps contraction near full extension has the
potential to generate large anterior tibialtranslation. The
patient may describe it as, “giving way”.
The strain on the ACL evoked by a quadriceps is
substantially diminished as the knee is flexed beyond 60
degrees.
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90. WB & NWB ACTIVITIES:
In NWB knee extension, the MA of the resistance
(weight of leg + external resistance) is minimal when
the knee is flexed to 90 degree, but increases as the
knee extension progresses. Therefore greater
quadriceps activity is required when knee approaches
full extension.
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91. The opposite happens in WB. In a standing squat, the
MA of the resistance (the superimposed body weight)
is minimal when knee is extended yet increases with
increasing knee flexion. Therefore greater quadriceps
activity is required with greater knee flexion.
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92. PATELLO-FEMORAL JOINT
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93. INTRODUCTION
It is an articulation between the posterior surface of
patella and the femoral condyles.
one of the most incongruent joints in the body.
The patella functions primarily as an anatomic pulley
for the quadriceps muscle and also reduces the
friction.
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94. PATELLOFEMORAL ARTICULAR
SURFACES & JOINT
CONGRUENCE:
In the fully extended knee, the patella lies on the
femoral sulcus. Because the patella has not yet
entered the inter-condylar groove, joint
congruency in this position is minimal.
The ratio of the length of the patellar tendon to the
length of the patella is approx1:1 and is referred to
as the Insall-SalvatiIndex.
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95. A markedly long tendon produces
an abnormally high position of the
patella on the femoral sulcus –
PATELLA ALTA.
An abnormally low position of the
patella –PATELLA BAJA.
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96. PATELLOFEMORAL ARTICULAR
SURFACES & JOINT
CONGRUENCE:
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97. KNEE JOINT -BIOMECHANICS
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98. KNEE JOINT -BIOMECHANICS
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99. KNEE JOINT -BIOMECHANICS
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100. MOTIONS OF THE PATELLA:
Motions of the patella are as follows:
Medial & lateral patellar tilt -about the longitudinal axis.
Medial & lateral rotation -antero-posterior axis.
the inferior pole being continually pointing towards tibial
tuberosity.
Medial & lateral patellar shift -is the simultaneous
translation of the patella that accompanies superior &
inferior glide.
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101. PATELLO-FEMORAL
JOINT STRESS:
The PF joint reaction force is influenced by both the
quadriceps force & knee angle.
As the knee flexes & extends, the patella is pulled by
the quadriceps tendon superiorly and simultaneously
by the patellar tendon inferiorly.
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102. FRONTAL PLANE
PATELLOFEMORAL STABILITY:
The longitudinal stabilizers of the patella consist of the
patellar tendon, quadriceps tendon, and the
patellotibialligament (extensor retinaculum).
The transverse stabilizers are composed of the
superficial portion of the extensor retinaculum.
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103. ASYMMETRY OF THE
PATELLOFEMORAL STABILIZATION:
This net effect of the
pull on patella is
assessed clinically by a
measurement called
the Q-angle.
Normal value: 10 –15
degrees (women have
slightly greater Q-angle
than men).
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104. Q-Angle
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105. WB v/s NWB EXERCISES with
PATELLOFEMORAL PAIN:
Each mode of exercise influence the
patellofemoraljoint differently on the
basis of the knee’s position within the
ROM.
It has been recommended that
those with the patello-femoral pain
should avoid deep flexion while
doing WB extension exercises and
avoid the final 30 degree of
extension while doing NWB knee
extension exercises.
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106. QUESTIONS???
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107. THANK YOU
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