Knee biomechanic

Dr. Pukhrambam Ratan khuman (PT)
M.P.T., (Ortho & Sports)

introduction
 Participating bones –
 Femur
 Tibia
 Patella

22 June 2012 Dr. Ratankhuman M.P.T., (Ortho & Sports) 2

Knee complex
 Tibio-femoral joint
 Patello-femoral joint


Tibio-femoral/Knee joint
 Ginglymus – (Hinge) ?
 A freely moving joint in which the bones are so
articulated as to allow extensive movement in
one plane.
 Arthodial – (Gliding) ?
 6 degrees of freedom
 3 Rotations
 3 Translations


Knee degree of freedom
 Rotations
 Flex/Ext – 150 – 1400
 Varus/Valgus – 60 – 80 in extension
 Int/ext rotation – 250 – 300 in flexion
 Translations
 AP 5 - 10mm
 Compression/Distraction 2 - 5mm
 Medial/Lateral 1-2mm


General Features of
Tibio-femoral Joint
 Double condyloid knee joint is also referred to as
Medial & Lateral Compartments of the knee.
 Double condyloid joint with 30 freedom of Angular
(Rotatory) motion.
 Flexion/Extension –
○ Plane – Sagittal plane
○ Axis – Coronal axis
 Medial/lateral (int/ext) rotation –
○ Plane – Transverse plane
○ Axis – Longitudinal axis
 Abduction/Adduction –
○ Plane – Frontal plane
○ Axis – Antero-posterior axis.


Femoral articular surface
 Femur is proximal articular surface of the knee
joint with large medial & lateral condyles.
 Because of obliquity of shaft, the femoral
condyles do not lie immediately below the
femoral head but are slightly medial to it.
 The medial condyle extend further distally, so
that, despite the angulation of the femur’s
shaft, the distal end of the femur remains
essentially horizontal.


 In sagittal plane - Condyles have a convex shape
 In the frontal plane - Slight convexity
 The lateral femoral condyle
 Shifted anteriorly in relation to medial
 Articular surface is shorter
 Inferiorly, the lateral condyle appears to be longer
 Two condyles are separated –
 Inferiorly by Intercondylar notch
 Anteriorly by an asymmetrical, shallow groove called
the Patellar Groove or Surface


Tibial articulating surface
 Asymmetrical medial & lateral tibial condyles
constitute the distal articular surface of knee joint.
 Medial tibial plateau is longer in AP direction than
lateral
 The lateral tibial articular cartilage is thicker than
the medial side.
 Tibial plateau slopes posteriorly approx 70 to 100
 Medial & lateral tibial condyles are separated by
two bony spines called the Intercondylar Tubercles


 The tibial plateaus are predominantly
flat, but convexity at anterior &
posterior margins
 Because of this lack of bony
stability, accessory joint structures
(menisci) are necessary to improve joint 9
o

congruency.


Menisci of knee joint
 2 asymmetrical fibro cartilaginous joint disk
called Menisci are located on tibial plateau.
 The medial meniscus is a semicircle & the
lateral is 4/5 of a ring (Williams, PL, 1995).


 Both menisci are –
 Open towards intercondylar
area
 Thick peripherally
 Thin centrally forming
cavities for femoral condyle
 By increasing
congruence, menisci play in
reducing friction between the
joint segment & serve as
shock absorber.


Meniscal attachment
 Common attachment of medial & lateral –
 Intercondylar tubercles of the tibia
 Tibial condyle via coronary ligaments
 Patella via patellomeniscal or patellofemoral ligament
 Transverse ligament between two menisci
 Anterior cruciate ligament (ACL)


Meniscal attachment
 Unique attachment of medial menisci –
 Medial collateral ligament (MCL)
 Semitendinous muscle
 Unique attachment of lateral menisci –
 Anterior & posterior meniscofemoral ligament
 Posterior cruciate ligament (PCL)
 Popliteus muscle


 Young children whose menisci have ample
of blood supply have low incidence of injury
 In adult, only the peripheral vascularized
region is capable of inflammation, repair &
remodeling following a tearing injury.
 Menisci are well innervated with free nerve
ending & 3 mechanoreceptors (Ruffine
corpuscle, Pacinian corpuscle & Golgi tendon organs)


TF alignment & weight
bearing force
 The anatomic/ longitudinal axis –
 Femur – Oblique, directed inferiorly & medially
 Tibia – Directed vertically
 The femoral & tibial longitudinal axis form an angle
medially at the knee joint of 1850 – 1900, i.e. 50 – 100
creating Physiological Valgus at knee
 In bilateral static stance – equal weight
distribution on medial & lateral condyle


 Deviation in normal force distribution –
 TF angle > 1900 – Genu Valgum – compress
lateral condyle
 TF angle < 1800 – Genu Varum – compress
medial condyle
 Compressive force in dynamic knee joint
 2 – 3 time body weight in normal gait
 5 – 6 time body weight in activities (like –
Running, Stair Climbing etc.)


Knee joint capsule
 Joint capsule enclose – TF & PF is large lax
 Outer portion – firmly attached to the inferior
aspect of femur & superior portion of tibia.
 Posterior attachment
 Proximally to posterior margins of the femoral
condyles and intercondylar notch.
 Distally to posterior tibial condyle.
 Anterior attachment
 Superiorly – Patella, tendon of quadriceps muscles
 Inferiorly patellar tendon complete the anterior
portion of the joint capsule.


 The antero-medial & antero-lateral portions
of the capsule, are often separately identified
as the medial and lateral patellar
retinaculae or together as the extensor
retinaculum.
 The joint capsule is reinforced
medially, laterally & posteriorly by capsular
ligaments.


Extensor retinaculum
 2 layers – superficial & deeper
 Deeper layer –
 Connecting the capsule anteriorly to menisci &
tibia via coronary ligament (known as
patellomeniscal or patellotibial band)
 Superficial layer –
 Mixed with vastus medialis & lateralis muscle &
distal continue to posterior femoral condyle
(patellofemoral ligament)


Synovial lining
 The intricacy of fibrous layer
capsule is surpassed by its
synovial lining except posteriorly.
 Synovium adheres to anterior
aspect & side to the ACL & PCL.
 Embryologically, the synovial
lining of the knee joint capsule is
divided by septa into 3 separate
compartment –
 Superior patellofemoral compartment
 2 separate medial & lateral
tibiofemoral compartment

Ligament of knee joint
 Collateral ligament
 Medial collateral ligament (MCL)
 Lateral collateral ligament (LCL)
 Cruciate ligament
 Anterior cruciate ligament (ACL)
 Posterior cruciate ligament (PCL)
 Posterior capsular ligament
 Meniscofemoral ligament
 Iliotibial band


MCL
 Attachment –
 Origin – medial aspect of medial femoral
condyle
 Insertion – proximal tibia
 Function –
 Resist valgus stress force (specially in
extended knee)
MCL
 Check lateral rotation of tibia
 Also restrain anterior displacement of tibia
when ACL is absent.


LCL
 Attachment –
 Origin – lateral femoral
condyle
 Insertion – posteriorly to head
of fibula
 Function –
 Resist varus stress force across
the knee
 Check combined lateral
rotation with posterior
displacement of tibia in
conjunction with tendon of
popliteal muscle.

Cruciate ligament
 Cruciate = “Resembling a cross” in
Latin.
 Located within the joint capsule &
are therefore called Intracapsular
PCL
Ligaments.
ACL
 Cruciate ligament provide stability in
sagittal plane
 The ACL & PCL are centrally
located within the capsule but lie
outside the synovial cavity.


ACL
 Attachment –
 Origin – from anterior surface the tibia in the
intercondylar area just medial to medial meniscus.
 It spans the knee laterally to PCL & runs in a superior
& posterior direction
 Insertion – to posteriorly on lateral condyle of femur
 ACL is divided into 2 bands –
 Antero-medial band (AMB)
 Postero-lateral band (PLB)


Function of acl
 Primarily –
 Check femur from being displaced posteriorly on the tibia
 Conversely, the tibia from being displaced anteriorly on femur.
 It tightens during extension, preventing excessive
hyperextension of the knee.
 ACL carried 87% of load when anterior translatory
force was applied to tibia with extended knee.
 Check tibial medial rotation by twisting around PCL
 ACL injury is common when knee is in flexed & tibia
rotated in either direction


PCL
 Attachment –
 Origin – from posterior tibia in intercondylar area
and runs in a superior and anterior direction on
medial side of ACL.
 Insertion - to anterior femur on the medial condyle
 PCL is divided into 2 bands –
 Antero-medial band (AMB)
 Postero-lateral band (PLB)


Function of pcl
 Primarily –
 Check femur from being displaced anteriorly on the tibia
or
 Tibia from being displaced posteriorly on femur.
 It tightens during flexion & is injured much less
frequently than ACL.
 PCL carry 93% of load when posterior translatory
force was applied to tibia with extended knee.
 PCL play a role in both restraining & producing
rotation of the tibia.


 Summary of ACL & PCL attachments –
 ACL – Runs from anterior tibia to posterior femur
 PCL – Runs from posterior tibia to anterior femur


Posterior capsular ligament
 Oblique popliteal ligament
 Posterior oblique ligament
 Arcuate ligament:
 Arcuate ligament lateral branch
 Arcuate ligament medial branch


Oblique popliteal ligament
 Attachment –
 Origin – The central part of posterior aspect of
the joint capsule
 Insertion - Posterior medial tibial condyle
 Function –
 Reinforces posteromedial knee joint capsule
obliquely on a lateral-to-medial diagonal from
proximal to distal


Posterior oblique ligament
 Attachment –
 Origin – Near the proximal origin of the MCL
and adductor tubercle
 Insertion – Posteromedial tibia, posterior capsule
& posteromedial aspect of the medial meniscus
 Function –
 Reinforces the posteromedial knee joint capsule
obliquely on a medial-to-lateral diagonal from
proximal to distal


Arcuate Ligament
Lateral Branch Medial branch
Distal
From posterior aspect of the head of the fibula
Attachment
Proximal To tendon of popliteus Into oblique popliteal lig on
Attachment muscle & posterior capsule medial side of joint
Reinforces the postero-lateral knee joint capsule
Function
obliquely on a medial to lateral from proximal to distal


Meniscofemoral ligament (MFl)
 There are 2 portions of
MFL, at least one in 91%
of knees & 30% knee
having both.
 MFL are not true
ligaments because they
attach bone to
meniscus, rather than bone
to bone.


Meniscofemoral ligament (MFl)
 Attachment –
 Origin – Both originate from posterior horn of lateral
meniscus
 Insertion – to lateral aspect of medial femoral condyle
○ The “Ligament of Humphry” or “Antero-MFL” is the
ligament run anterior to PCL on tibia
○ The “Ligament of Wrisberg” or “Postero-MFL” is the
ligament run posterior to PCL, also known as “3rd Cruciate
Ligament of Robert”
 Function –
 They may assist PCL in restraining posterior tibial translation
 Also assist popliteus muscle by checking tibial lateral rotation

Bursa associated with knee
 Pre-patellar bursa –
 Located between the skin & anterior surface of patella
 They allows free movement of skin over patella during
knee flexion & extension
 Subcutaneous bursa –
 Located between patellar ligament & overlying skin
 Deep infra-patellar bursa –
 Located between patellar ligament & tibial tuberosity
 Helps in reducing friction between the patellar
ligament & tibial tuberosity


Function of knee joint
 Osteokinemetic of knee joint –
 Primary motions –
○ Flexion / Extension
○ Medial / Lateral Rotation
 Secondary motions –
○ Antero-posterior displacement of femur or tibia
○ Abduction / Adduction through valgus or varus force


Flexion & extension
 Axis – no fixed axis but move through ROM
(frontal axis)
 Plan – sagittal plan
 ROM of flexion / extension –
 Flexion – 1300 – 1400
 Extension – 50 – 100 (Consider normal, beyond
this termed as Genurecurvatum)
 In close kinematic chain (OKC) – flexion /
extension range is limited by ankle range.


Medial / lateral rotation
 Axis – Longitudinal / Vertical axis
 Plan – Transvers plan
 ROM at 900 knee flexion –
 Lateral rotation – 00 – 400
 Medial rotation – 00 – 300


TF CKC Flexion
 Early 00 - 250 knee flexion –
 Posterior rolling of femoral
condyles on the tibia
 As flexion continues –
 Posterior Rolling accompanied by
simultaneous Anterior glide of femur
 Create a pure Spin of femur on the
posterior tibia


TF CKC extension
 Extension from flexion is a
reversal of flexion motion.
 Early extension –
 Anterior rolling of femoral
condyles on tibial plateau
 As extension continues –
 Anterior Rolling accompanied by
simultaneous Posterior glide of
femur
 Produce a pure Spin of femoral
condyles on tibial plateau

Tf ock flexion / extension
 When tibia is flexed on a fixed femur –
 The tibia performed Both Posterior Rolling &
Gliding on relatively fixed femoral condyles.

 When tibia is Extended on a fixed femur –
 The tibia performed Both Anterior Rolling &
Gliding on relatively fixed femoral condyles.


Locking of knee joint
 CKC femoral extension from 300 flexion –
 Larger medial femoral condyle continue rolling & gliding
posteriorly when smaller lateral side stopped.
 These result in medial rotation of femur on tibia, seen in last
50 of extension.
 The medial rotation of femur at final stage of extension is
not voluntary or produce by muscular force, which is
referred as “Automatic” or “Terminal Rotation”.
 The rotation within the joint bring the joint into a closed
packed or Locked position.
 The consequences of automatic rotation is also known as
“Locking Mechanism” or “Screw Home Mechanism”.
 OKC – lateral rotation of tibia on fixed femur

Unlocking of knee joint
 To initiate flexion, knee must be unlocked.
 A flexion force will automatically result in lateral
rotation of femur
 Because the larger medial condyle will move before
the shorter lateral condyle.
 Popliteus is the primary muscle to unlocked the knee.


TF CKC Flexion: ACL Control
At full extension –
 Angle of ACL
inclination greatest
 Anterior directed
component force will
eventually Restrain
Posterior Femoral Roll


TF CKC Flexion: ACL Control
cont…
 As TF flexion increases –
 Angle of ACL inclination
decreases
 Anterior directed
component force increases
sufficient enough to
produce Anterior Femoral
Slide


Hyperextension Impact on
ACL
 End ROM extension
brings the mid-
substance of the ACL in
contact with the femoral
intercondylar shelf
(notch of Grant)
 This contact point acts
as a fulcrum to tension
load the ACL


TF CKC Flexion: PCL Control
 Angle Of PCL Inclination
is greatest at full flexion.
 Anterior directed
component force will
eventually Restrain
Posterior Femoral Roll


TF CKC Extension: PCL Control
 As TF extension increases –
 Angle Of PCL Inclination
decreases
 Posterior directed component
force increases sufficient enough
to Produce Posterior Femoral
Slide


TF OKC Extension Arthrokinematics
sagittal plan
 Extension –
 Meniscal migrate Anteriorly –
○ Because of meniso-patellar
ligament

Menisco-patellar
Ligaments

TF OKC flexion Arthrokinematics
sagittal plan
 Flexion – Menisci migrate posteriorly because of
 Semimembranosis attachment to medial meniscus
 Popliteus attachment to lateral meniscus


Knee axial rotation


Axial rotation of knee
arthrokinemetic
 Axis – vertical axis
 Plan – transvers plan
 ROM – Maximum range is
available at 90 of knee flexion.
 The magnitude rotation diminishes
as the knee approaches both full
extension and full flexion.
 Medial condyle acts as pivot point
while the lateral condyles move
through a greater arc of motion,
regardless of direction of rotation.


rotation of tibia
 During Tibial lateral rotation on the femur –
 Medial tibial condyle moves slightly anteriorly on
the relatively fixed medial femoral condyle, whereas
lateral tibial condyle moves a larger distance
posteriorly.
 During tibial medial rotation –
 Medial tibial condyle moves only slightly
posteriorly, whereas the lateral condyle moves
anteriorly through a larger arc of motion.


 During both medial and lateral rotation –
 The menisci reduce friction & distribute femoral
condyle force created on the tibial condyle
without restricting the motion.
 Meniscus also maintain the relationship of tibia
& femoral condyles just as they did in flexion
and extension.


Valgus (Abduction)/Varus
(Adduction)
 Axis – Antero-posterior axis
 Plan – Frontal plane
 ROM –
 8 at full extension
 13 with 20 of knee flexion.
 Excessive frontal plane motion could
indicate ligamentous insufficiency


pFj function
 It work primarily as an anatomical pulley
 It reduce friction between quadriceps tendon
& femoral condyle.
 The ability of patella to perform its function
without restricting knee motion depends on
its mobility.


PFJ articulating surface
 The triangular shape patella is a largest sesamoid
bone in body is a least congruent joint too.
 Posterior surface is divided by a vertical ridge into
medial & lateral patellar facets.
 The ridge is located slightly towards the medial
facet making smaller medial facet
 The medial & lateral facet are flat & slightly
convex side to side & top to bottom.
 At least 30% of patella have 2nd ridge separating
medial facet from the extreme medial edge known
as Odd Facet of Patella.

Femoral articulating surface

 Patella articulate in femur
with intercondylar groove
or femoral sulcus on
anterior surface of distal
femur.
 Femoral surface are
concave side to side &
convex top to bottom but
lateral facet is more convex
then medial surface.


PFJ congruence
 The vertical position of patella in femoral sulcus
is related to length of patellar
tendon, approximately 1:1 is (referred to as
Insall-Salvati index)
 An excessive long tendon produce an abnormally
high position of patella on femoral sulcus known
as patella alta.
 In neutral or extended knee, the patella has little
or no contact with the femoral sulcus beneath.


 At 100 – 200 of flexion – contact with
inferior margin of medial & lateral
facet.
 By 900 of flexion – all portion of
patella contact with femur except the
odd facet.
 Beyond 900 of flexion – medial
condyle inter the intercondylar notch
& odd facet achieves contact for the
first time.
 At 1350 of flexion – contact is on
lateral & odd facet with medial facet
completely out of contact.

Medial-lateral PFJ stability
 PFJ is under permanent control of 2 restraining
mechanism across each other at right angel.
 Transvers group of stabilizer
 Longitudinal group of stabilizer


 Transvers stabilizer –
 Medial & lateral retinaculum
 Vastus Medialis & Lateralis
 The lateral PF ligament contributes 53% of total
force when in full extension of knee.


Longitudinal stabilization
 Patellar tendon – inferiorly
 Quadriceps tendon – superiorly


Medial-lateral positioning of
patella / patellar tracking
 When the knee is fully extended & relax, the
patella should be able to passively displaced
medially or laterally not more then one half of
patella.
 Imbalance in passive tension or change in line
of pull of dynamic structures will substantially
influence the patella.
 Abnormal force may influence the excursion of
patella even in its more secure location within
intercondylar notch in flexion.


Medial & lateral force on
patella
 Since the action line of quadriceps & patellar
ligament do not co-inside, patella tend to pulled
slightly laterally & increase compression on
lateral patellar facets.
 Larger force on patella may cause it to
subluxation or dislocate off the lateral lip of
femur.
 Genu valgum increase the obliquity of femur &
oblique the pull of quadriceps.


 Femoral anteversion & tibial torsion creates an
increased obliquity in patella predisposing to
excessive lateral pressure or to subluxation or
dislocation.
 Excessive tension in lateral retinaculum (or
weakness of VMO) may cause the patella to tilt
laterally.
 Insufficient height of lateral lips of femoral
sulcus may create patellar subluxation or fully
dislocation, even with relatively small lateral
force.


Muscles of knee
&
its function


Muscles of the Knee
Area One-joint Muscle Two-joint Muscle
Vastus Lateralis
Anterior vastus Medialis Rectus Femoris
Vastus Intermedialis
Biceps Femoris (Long)
Semimembranosus
Biceps Femoris Semitendinosus
Posterior
(Short) Sartorius
Gracilis
Gastrocnemius
Lateral Tensor Fascia Latae


Muscles of Posterior Knee
Semimembranosus, Semitendinosus, Biceps
Knee Flexors Femoris (Long & Short Heads), Sartorius,
Gracilis, Popliteus & Gastrocnemius Muscles
Flex + Tibial Popliteus, Gracilis, Sartorius, Semimembranosus
Medial Rotators & Semitendinosus Muscles
Flex + Tibial
Biceps Femoris
Lateral Rotator
Flex + Biceps Femoris, Lateral Head Gastrocnemius &
Abductor Popliteus
Flex + Semimembranosus, Semitendinosus, Medial Head
Adductor Gastrocnemius, Sartorius & Gracilis


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Knee flexor groups
 7 muscles flex the knee [Semimembranosus,
Semitendinosus, Biceps Femoris (Long & Short
Heads), Sartorius, Gracilis, Popliteus &
Gastrocnemius Muscles].
 5 muscles of flexors (Popliteus, Gracilis,
Sartorius, Semimembranosus & Semitendinosus
Muscles) –
 They have the potential to medially rotate the tibia on
a fixed femur
 Whereas the biceps femoris is capable of rotating the
tibia laterally.

Knee flexor groups cont…
 The lateral muscles (Biceps Femoris,
Lateral Head of Gastrocnemius, &
Popliteus)
 Capable of producing valgus moments at knee
 The medial muscles (Semimembranosus,
Semitendinosus, Medial Head of
Gastrocnemius, Sartorius & Gracilis)
 Can generate varus moments


biceps femoris or Lateral
Hamstring
 Proximal attachments: By two heads:
 Long head – to the tuberosity of
ischium, having a common tendon of
attachment with semitendinosus.
 Short head – to the lower portion of shaft of
femur & to lateral intermuscular septum.
 Distal attachments:
 2 heads unite to be attached to the head of
fibula, to the lateral condyle of the tibia &
to the fascia of leg.
 AXN:
 Hip extension & external rotation
 Knee flexion & external rotation.


Semitendinosus or medial
hamstring
 Proximal attachment:
 Tuberosity of ischium, having a
common tendon with the long
head of the biceps.
 Distal attachment:
 Medial aspect of tibia near the
knee joint, distal to the attachment
of the gracilis.
 AXN:
 Hip extension and internal rotation
 Knee flexion and internal rotation.

semimembranosus
 Tuberosity of the ischium
 Medial condyle of the tibia.
 AXN:
 Knee flexion and internal rotation
 Hip extension and internal rotation.


Gastrocnemius
 Proximal attachments:
 Above the femoral condyles and span the knee joint
on the flexor side.
 The muscular portion of the gastrocnemius may be
seen contracting in resisted flexion of the knee.
 Because the gastrocnemius is more important as a
plantar flexor of the ankle than as a knee flexor
 Distal attachments:
 To the posterior calcaneus


Popliteus
 By a strong tendon from the lateral condyle of
the femur.
 The muscle fibers take a downward medial
course and are attached into proximal posterior
portion of body of tibia.
 widespread in a proximal-distal
direction, giving the muscle a somewhat
triangular shape.
 AXN:
 Medial rotation and flexion of knee.


Muscle passing medial knee


Anterior Muscles
 Quadriceps muscles
comprise 4 muscles that
cross the anterior knee
 Rectus femoris
 Vastus lateralis
 Vastus Intermedialis
 Vastus Medialis


Quadriceps muscle
 Functions –
 Together, the 4 components of quadriceps femoris muscle
function to extend the knee.
 Rectus femoris being a 2 joint muscle, it also involved in hip
flexion along with knee extension.
 Angle of pull of Quadriceps –
 Vastus lateralis – Pull 350 Lateral to long axis of femur
 Vastus Intermedius – Pull Parallel to Shaft of femur, making
purest knee extensor.
 Vastus Medialis – Pull depended on segment of muscle –
○ Upper fibers Vastus Medialis Longus (VML) angled 150 – 180 Medially
○ Distal fibers Vastus Medialis Oblique (VMO) angled 500 – 550 Medially


Patellar Influence on
Quadriceps Function
 Patella lengthens the MA of quadriceps by
increasing the distance of quadriceps tendon &
patellar tendon from the axis of the knee joint.
 The patella, as an anatomic pulley, deflects the
action line of quadriceps away from the joint
centre, increasing the angle of pull & enhancing
extension torque generation.
 Pull of quadriceps also creates anterior translation
of tibia on femur increasing ACL restraint


Quadriceps activities
During weight-bearing
 When an erect posture is attained –
 Minimal activity of quadriceps because the LOG
passes just anterior to knee axis results in a
gravitational extension torque that maintains the joint
in extension.
 In weight-bearing with the knee slightly flexed –
 The LOG pass posterior to knee joint axis
 As the gravitational torque tend to promote knee
flexion, the activity of quadriceps is necessary to
counterbalance the gravitational torque and maintain
the knee joint in equilibrium.


LOG & Movement arm (MA)
during squatting


Quadriceps activities during
non–weight-bearing
 The MA of resistance is minimal when the knee
is flexed to 900 but increases as knee extension
progresses.
 Therefore, greater quadriceps force is required
as the knee approaches full extension.
 The opposite happens during weight-bearing
activities.


LOG & Movement arm (MA)
during non-weight bearing


Quadriceps Strengthening:
Weight-Bearing versus Non–Weight-
Bearing
 Weight-bearing quadriceps exercises as squat
& leg press resulted in a posterior shear force
at knee throughout the entire ROM
 There was No Anterior Shear anywhere in
the ROM.
 In contrast, anterior shear force in a non–
weight bearing knee extension exercise
maximal anterior shear occurring between
200 and 100.

Quadriceps Strengthening:
Weight-Bearing versus Non–
Weight-Bearing cont…
 A Posterior Shear Force was also found
during Non–Weight-Bearing Exercise, only
between 600 and 1010 of flexion.
 Weight Bearing Exercises are often
prescribed after ACL or PCL injury because
of less stressful, more like functional
movements & safer than non–weight-bearing
exercises.


Other muscles helping
knee extension
 The actions of the Gluteus Maximus
& Soleus Muscles can influence
knee motion in weight-bearing.
 Although they do not cross the knee
joint, these muscles are capable of
assisting with knee extension.


Iliotibial Band or IT tract
 Proximally – GM
 The IT band is from Tensor TFL
Fascia Lata (TFL), Gluteus
Maximus & Gluteus Medius
muscles.
 Distally –
 Attach to lateral intermuscular
septum & inserts into the
Anterolateral Tibia (Gerdy’s
Tubercle).
 IT band also attaches to
patella via lateral PF ligament ITB
of lateral retinaculum.


 AXN:
 Reinforcing anterolateral aspect of knee joint
 Assisting ACL in checking posterior femoral or
anterior tibial translation when the knee joint is nearly
full extension.
 With the knee in flexion, the combination of IT
band, LCL & popliteal tendon increases the stability of
lateral knee.


AXN line for itb
 In extended knee –
 IT band moves anterior to the knee joint axis.
 In flexed knee –
 IT band moves posteriorly over the lateral femoral
condyle as the knee is flexed.
 The IT band, therefore, remains consistently
taut, regardless of hip or knee’s position.


Stabilization of knee joint
 Classification of supporting structure of knee –
 Functional –
○ Static stabilizer
○ Dynamic stabilizer
 Structural –
○ Capsular method
○ Extra-capsular method
 Location –
○ Medial joint compartment
○ Lateral joint compartment


Static stabilizer
 It include the passive structures, such as –
 Capsule
 Ligaments –
○ Meniscopatellar lig,
○ PF lig,
○ MCL & LCL,
○ ACL & PCL,
○ Oblique poplitial &
○ Transverse lig.


Dynamic stabilizer
 It includes following muscles & oponeuroses –
 Quadriceps femoris,
 IT band,
 Extensor retinaculum,
 Poplitius,
 Pes anserinus,
 Hamstrings and also
 Gastrocnemius


Medial joint stabilizers
 Structure includes –
 Medial patellar retinaculum,
 MCL,
 Oblique poplitial ligament &
 PCL


Lateral joint stabilizers
 The structure included in static & dynamic
stabilization of knee –
 IT band,
 Biceps femoris,
 Popliteus,
 LCL,
 Meniscofemoral arcuate,
 ACL &
 Lateral patellar retinaculum


Knee Joint Stabilizers
Direction Structures Functions
• Anterior cruciate ligament
• Iliotibial band
• Hamstring muscles
• Soleus muscle (in weight-
bearing)
A-P/ • Gluteus maximus muscle Limit anterior tibial
Hyperextension (in weight-bearing) (or posterior
stabilizers • Posterior cruciate ligament femoral) translation
• Meniscofemoral ligaments
• Quadriceps muscle
• Popliteus muscle
• Medial & lateral heads of
gastrocnemius

• Medial collateral ligament
• Posterior cruciate ligament
• Arcuate ligament
• Posterior oblique ligament
Limits valgus of tibia
• Sartorius muscle
• Gracilis muscle
• Semitendinosus muscle
Varus/valgus • Semimembranosus muscle
stabilizers • Medial head of gastrocnemius muscle
• Lateral collateral ligament
• Iliotibial band
Limit Varus of tibia
• Arcuate ligament
• Posterior oblique ligament
• Biceps femoris muscle
• Lateral head of gastrocnemius muscle

Limit medial rotation of
• Posteromedial capsule
tibia
• Meniscofemoral ligament
• Biceps femoris
Internal/external • Posterolateral capsule
rotational stabilizers • Medial collateral ligament
• Lateral collateral ligament
• Popliteus muscle Limit lateral rotation of
• Sartorius muscle tibia
• Gracilis muscle Semitendinosus
muscle
• Semimembranosus muscle


References
 Joint Structure and Function: A Comprehensive
Analysis, Fourth Edition, Cynthia C. Norkin, 2005
 Joint Structure and Function: A Comprehensive
Analysis, Third Edition, Cynthia C. Norkin
 Clinical Kinesiology and Anatomy, Fourth
Edition, Lynn S. Lippert, 2006
 Basic Biomechanics of the Musculoskeletal
System, third edition, Margareta Nordin


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