Joint Capsule:Joint Capsule:• Encloses the tibiofemoral & patellofemoral Encloses the tibiofemoral & patellofemoral

jointsjoints• It is large complex and possess several It is large complex and possess several

recessesrecesses• Collaterals reinforce the sides of the capsuleCollaterals reinforce the sides of the capsule• Anteromedial and anterolateral portions of Anteromedial and anterolateral portions of

capsule are known as capsule are known as medialmedial and and laterallateral patellar retinaculapatellar retinacula

Ligaments:Ligaments:• As the joint lacks bony restraint to any motions, As the joint lacks bony restraint to any motions,

ligaments are credited with resisting or controllingligaments are credited with resisting or controlling

a.a. Excessive extensionExcessive extension

b.b. Varus and valgus stressVarus and valgus stress

c.c. Anterior and posterior displacement of tibia Anterior and posterior displacement of tibia beneath the femurbeneath the femur

d.d. Medial or lateral rotation of of tibia beneath the Medial or lateral rotation of of tibia beneath the femurfemur

e.e. Combinations of anteroposterior displacements Combinations of anteroposterior displacements and rotations of tibia – rotatory stabilization and rotations of tibia – rotatory stabilization

I.I. Collateral Ligaments:Collateral Ligaments:• Are taught in full extension and help Are taught in full extension and help

resist hyper extension of knee jointresist hyper extension of knee joint

1.1. Medial collateral ligament:Medial collateral ligament:• Extends from medial femoral epicondyle Extends from medial femoral epicondyle

to medial aspect of proximal tibiato medial aspect of proximal tibia• Resists valgus stressResists valgus stress• Backup restraint to Backup restraint to

pure anterior displacement pure anterior displacement

of tibia when ACL is absent of tibia when ACL is absent

2.2. Lateral collateral ligament:Lateral collateral ligament:• Extends from lateral femoral epicondyle Extends from lateral femoral epicondyle

to head of fibulato head of fibula• Resists varus stressResists varus stress

II.II. Cruciate ligaments:Cruciate ligaments:• Two in number and named according to Two in number and named according to

their tibial attachmentstheir tibial attachments

1.1. Anterior cruciate ligament:Anterior cruciate ligament:• arises from anterior aspect of tibia passes arises from anterior aspect of tibia passes

under the transverse ligament and extends under the transverse ligament and extends superiorly and posteriorly and attaches to superiorly and posteriorly and attaches to posterior part of inner aspect of lateral posterior part of inner aspect of lateral femoral condylefemoral condyle

• primary restraint to anterior displacement primary restraint to anterior displacement of tibia on femoral condylesof tibia on femoral condyles

• fascicles are grouped into anteromedial fascicles are grouped into anteromedial band (AMB) and posterolateral band (AMB) and posterolateral band(PLB)band(PLB)

2.2. Posterior cruciate ligament:Posterior cruciate ligament:• arises from posterior aspect of tibia and arises from posterior aspect of tibia and

attaches to inner aspect of medial femoral attaches to inner aspect of medial femoral condylecondyle

• is shorter and less obliqueis shorter and less oblique• primary restraint to posterior displacement primary restraint to posterior displacement

of tibia beneath the femurof tibia beneath the femur• fascicles are grouped into anteromedial fascicles are grouped into anteromedial

band (AMB) and posterolateral band (AMB) and posterolateral band(PLB) band(PLB)

III.III. Posterior Capsular Ligaments:Posterior Capsular Ligaments:• Postero medial aspect of capsule is Postero medial aspect of capsule is

reinforced by reinforced by oblique popliteal oblique popliteal ligamentligament expansion of semimebranous expansion of semimebranous musclemuscle

• Postero lateral aspect of Postero lateral aspect of

capsule is reinforced by capsule is reinforced by

arcuate popliteal ligamentarcuate popliteal ligament

expansion of popliteus muscleexpansion of popliteus muscle• Both check hyperextensionBoth check hyperextension

IV.IV. Meniscofemoral Ligaments:Meniscofemoral Ligaments:• Two in number, arise from posterior Two in number, arise from posterior

horn of lateral meniscus and insert on the horn of lateral meniscus and insert on the lateral aspect of medial femoral condyle lateral aspect of medial femoral condyle near insertion site of PCLnear insertion site of PCL

• Ligament that runs anterior to PCL is Ligament that runs anterior to PCL is lig. lig. of Humphrey/anterior meniscofemoral of Humphrey/anterior meniscofemoral ligamentligament

• Ligament that runs posterior to PCL is Ligament that runs posterior to PCL is lig.of Wrisberg/ posterior lig.of Wrisberg/ posterior meniscofemoral ligamentmeniscofemoral ligament

Bursae:Bursae:• Supra patellar bursaSupra patellar bursa• Sub popliteal bursaSub popliteal bursa• Gastronemius bursaGastronemius bursa• Prepatellar bursaPrepatellar bursa• Infrapatellar bursaInfrapatellar bursa• Deep infrapatellar bursaDeep infrapatellar bursa

• Synovial fluid contained in knee capsule Synovial fluid contained in knee capsule moves from recess to recess during moves from recess to recess during movements of kneemovements of knee

• In extension fluid is shifted anteriorlyIn extension fluid is shifted anteriorly• In flexion fluid is forced posteriorlyIn flexion fluid is forced posteriorly• In semiflexed position fluid is under least In semiflexed position fluid is under least

tensiontension

Knee Joint Motion:Knee Joint Motion: • Primary movements are flexion/extension Primary movements are flexion/extension

and to lesser extent medial/lateral rotationand to lesser extent medial/lateral rotation

Osteokinematics:Osteokinematics:

Flexion/extension:Flexion/extension:• As many two joint muscles pass knee they As many two joint muscles pass knee they

can affect the ROM with changes in hip can affect the ROM with changes in hip positionposition

Knee Flexion:Knee Flexion: Passive 130° - 140°. Passive 130° - 140°.• Range is limited to 120° if hip is Range is limited to 120° if hip is

hyperextended as hamstring becomes hyperextended as hamstring becomes actively insufficientactively insufficient

• Gait requires about 60° of knee flexionGait requires about 60° of knee flexion• This increases to about 80° for staircase This increases to about 80° for staircase

climbing and 90° for sitting down into a climbing and 90° for sitting down into a chairchair

Knee Extension:Knee Extension: 5° - 10° normal 5° - 10° normal

• Excessive hyperextension is called as Excessive hyperextension is called as Genu Genu RecurvatumRecurvatum

Rotation:Rotation:• Knee rotates in 2 different directionsKnee rotates in 2 different directions• Axial rotation provides second degree of freedom Axial rotation provides second degree of freedom

to tibiofemoral jointto tibiofemoral joint• Medial and lateral rotation are named for the Medial and lateral rotation are named for the

relative motion of tibiarelative motion of tibia• Occurs due to ligament laxity and articular Occurs due to ligament laxity and articular

incongruenciesincongruencies • Depends on joint positionDepends on joint position• In full extension there is no axial rotationIn full extension there is no axial rotation• As the knee flexes towards 90° the ligaments lax As the knee flexes towards 90° the ligaments lax

and the condyles are free to moveand the condyles are free to move• Maximum axial rotation is available at 90°Maximum axial rotation is available at 90°• Lateral Rotation:Lateral Rotation: 0 - 40° 0 - 40°• Medial Rotation:Medial Rotation: 0 - 30° 0 - 30°

Arthrokinematics :Arthrokinematics :• Large articular surface of femur and relatively small Large articular surface of femur and relatively small

tibial condyle creates a potential problem as femur tibial condyle creates a potential problem as femur begins to flex on tibiabegins to flex on tibia

• If femoral condyles were If femoral condyles were

permitted to roll posteriorly permitted to roll posteriorly

on tibial condyle femur would on tibial condyle femur would

run out of tibial condyles run out of tibial condyles

before much flexion could before much flexion could

occur – this would result in occur – this would result in

limitation of flexion or femur limitation of flexion or femur

would roll of tibiawould roll of tibia

• For femoral condyles to continue to roll with For femoral condyles to continue to roll with increased flexion of the femur the condyles increased flexion of the femur the condyles must simultaneously glide anteriorly on tibial must simultaneously glide anteriorly on tibial condyle to prevent them from rolling condyle to prevent them from rolling posteriorly off the tibial condyleposteriorly off the tibial condyle

Knee flexion:Knee flexion:• First part of flexion of femur from full extension First part of flexion of femur from full extension

(0-25°) is primarily (0-25°) is primarily rollingrolling of femoral condyles on of femoral condyles on the tibia bringing the contact of femoral condyles the tibia bringing the contact of femoral condyles posteriorly on tibial condyleposteriorly on tibial condyle

• As flexion continues the rolling is accompanied by As flexion continues the rolling is accompanied by an an anterior glideanterior glide just sufficient to create a nearly just sufficient to create a nearly pure spin of the femurpure spin of the femur

• That is, the magnitude of posterior displacement That is, the magnitude of posterior displacement that would occur with the rolling of condyles is that would occur with the rolling of condyles is offset by the anterior glideoffset by the anterior glide

• This results in a linear displacement after 25This results in a linear displacement after 25 of of flexionflexion

• The The anterior glide anterior glide is controlled by tensionis controlled by tension encountered in theencountered in the ACLACL as the femur rolls as the femur rolls posteriorly only on the tibial condylesposteriorly only on the tibial condyles

• The glide is facilitated by the wedge shape of The glide is facilitated by the wedge shape of the the meniscusmeniscus

• The femur and the menisci create shear force The femur and the menisci create shear force with respect to one another, thus the menisci with respect to one another, thus the menisci accompany the femoral condyles as they accompany the femoral condyles as they move posteriorly on the tibial condylesmove posteriorly on the tibial condyles

• The lateral meniscus moves more than the The lateral meniscus moves more than the medialmedial

Knee extension:Knee extension:• Occurs initially as a rolling of the femoral Occurs initially as a rolling of the femoral

condyles over the tibial condyles displacing condyles over the tibial condyles displacing the femoral condyles the femoral condyles anteriorlyanteriorly back back to the to the neutral positionneutral position

• After the initial forward rolling, femoral After the initial forward rolling, femoral condyles condyles glide posteriorlyglide posteriorly just enough to just enough to continue extension of the femur as a pure spincontinue extension of the femur as a pure spin

• Tension in the PCLTension in the PCL and the shape of the and the shape of the menisci facilitate the intra articular menisci facilitate the intra articular movements of femoral condyles during knee movements of femoral condyles during knee extensionextension

• Motion (or distortion) of menisci are an Motion (or distortion) of menisci are an important component of the movementsimportant component of the movements

• Failure to distort would result in limitation Failure to distort would result in limitation of ROMof ROM

Locking and unlockingLocking and unlocking::• Although the incongruence of the femoral Although the incongruence of the femoral

condyles and the tibial condyles results in a condyles and the tibial condyles results in a rolling and gliding of the condylar surfaces rolling and gliding of the condylar surfaces on each other, the asymmetry in the size of on each other, the asymmetry in the size of medial and lateral condyles also causes medial and lateral condyles also causes complex intra-articular motionscomplex intra-articular motions

Locking:Locking:• In weight bearing closed chain position In weight bearing closed chain position

extension of the femur on a fixed tibia extension of the femur on a fixed tibia results in additional motion to the earlier results in additional motion to the earlier explained onesexplained ones

• As the As the femurfemur extends to about 30° of flexion,extends to about 30° of flexion, the the shorter lateral condylesshorter lateral condyles complete its rolling – gliding complete its rolling – gliding motionmotion

• As extension continues the longer medial femoral As extension continues the longer medial femoral condyle continues to roll and condyle continues to roll and glide posteriorlyglide posteriorly although the lateral condyle has haltedalthough the lateral condyle has halted

• This continued motion of medial femoral condyles This continued motion of medial femoral condyles results in results in medial rotation of the femur medial rotation of the femur on on tibia,tibia, pivoting about the fixed lateral condylepivoting about the fixed lateral condyle

• This medial rotation is most evident in the final stages This medial rotation is most evident in the final stages of knee extension (5of knee extension (5))

• Increasing tension in the joint ligaments as the knee Increasing tension in the joint ligaments as the knee approaches full extension may also contribute to the approaches full extension may also contribute to the rotation with in the jointrotation with in the joint

• Since the medial rotation of the femur that Since the medial rotation of the femur that accompanies the final stages of knee extension accompanies the final stages of knee extension is not voluntary or produced by muscular is not voluntary or produced by muscular forces, it is referred to as forces, it is referred to as automatic or terminal automatic or terminal rotationrotation

• This rotation brings the knee inThis rotation brings the knee in close-packed or close-packed or locked positionlocked position

• The tibial tubercles are lodged in the The tibial tubercles are lodged in the intercondylar notch,intercondylar notch, the ligaments become taut the ligaments become taut and the menisci are interposed tightly between and the menisci are interposed tightly between the condyles - the condyles - locking mechanism or screw locking mechanism or screw home mechanismhome mechanism

UnlockingUnlocking::• To initiate flexion knee must be To initiate flexion knee must be unlocked unlocked • For the knee to flex, unlocking occurs by For the knee to flex, unlocking occurs by

lateral rotation of the femurlateral rotation of the femur• A flexion force will automatically result in A flexion force will automatically result in

lateral rotation since the longer medial side lateral rotation since the longer medial side will move before the shorter lateral sidewill move before the shorter lateral side

• The longer medial side moves just compared The longer medial side moves just compared to the lateral sideto the lateral side

• In open chain - Tibia rotates laterally on a fixed In open chain - Tibia rotates laterally on a fixed femur during the last 30femur during the last 30 of of extension –LOCKINGextension –LOCKING

• Tibia rotates medially on a fixed femur before Tibia rotates medially on a fixed femur before flexion can proceed - UNLOCKINGflexion can proceed - UNLOCKING

MusclesMuscles

I.I. Flexors:Flexors:

a.a. SemimembranosusSemimembranosus

b.b. Gastrocnemius Gastrocnemius

c.c. SartoriusSartorius

d.d. GracilisGracilis

Gracilis, semitendinosis and sartorius are Gracilis, semitendinosis and sartorius are inserted on the tibia by means of a inserted on the tibia by means of a common tendon called as common tendon called as ‘Pes ‘Pes Anserinus’Anserinus’

e.e. Popletius Popletius

II.II. Extensors:Extensors: Quadriceps femorisQuadriceps femoris Only muscle which crosses two Only muscle which crosses two

joints is rectus femorisjoints is rectus femorisPatella increases the efficiency of quadricepsPatella increases the efficiency of quadriceps• Efficiency of the quadriceps muscle is Efficiency of the quadriceps muscle is

affected by the patellaaffected by the patella• Patella lengthens the moment arm of Patella lengthens the moment arm of

quadriceps by increasing the distance of quadriceps by increasing the distance of the quadriceps tendon and patellar the quadriceps tendon and patellar ligament from the axis of the knee jointligament from the axis of the knee joint

• Patella acting as an anatomic pulley deflects Patella acting as an anatomic pulley deflects the action line of the quadriceps femoris the action line of the quadriceps femoris away from the joint that increases the angle away from the joint that increases the angle of pull and the ability of the muscle to of pull and the ability of the muscle to generate torquegenerate torque

• It helps to reduce friction between the tendon It helps to reduce friction between the tendon and the condylesand the condyles

• Substantial decreases in the strength of Substantial decreases in the strength of quadriceps of upto 49% occurs following quadriceps of upto 49% occurs following patellectomy patellectomy

Patellofemoral joint :Patellofemoral joint :• Patella is primarily an anatomic pulley and reduces Patella is primarily an anatomic pulley and reduces

friction between quadriceps and femoral condylesfriction between quadriceps and femoral condyles• Ability of patella to perform its functions with out Ability of patella to perform its functions with out

restricting the knee motion depends on its mobilityrestricting the knee motion depends on its mobility

Patellar flexion:Patellar flexion:• In full extension patella sits on anterior surface on In full extension patella sits on anterior surface on

distal femurdistal femur• With knee flexion patella slides distally on femoral With knee flexion patella slides distally on femoral

condyles,seating itself between femoral condylescondyles,seating itself between femoral condyles• In full flexion patella sinks into the intercondylar In full flexion patella sinks into the intercondylar

notchnotch

Patellar extension:Patellar extension:• Knee extension reverses the sliding of the Knee extension reverses the sliding of the

patella and brings it back to the patella patella and brings it back to the patella surface of femursurface of femur

Patellar tilt:Patellar tilt:• Tilts medially from Tilts medially from

0°-30°0°-30°• Tilts laterally between Tilts laterally between

20° -100°20° -100°

Patellar RotationPatellar Rotation : :• Medial rotation of the patella involves Medial rotation of the patella involves

movement of the inferior patellar pole with movement of the inferior patellar pole with medial rotation of the tibia medial rotation of the tibia

• Lateral rotation of the patella involves Lateral rotation of the patella involves movement of the inferior pole of patella movement of the inferior pole of patella with lateral rotation of the tibiawith lateral rotation of the tibia

Patellar Shift:Patellar Shift:• Mediolateral translation that the patella Mediolateral translation that the patella

under goes during knee movementunder goes during knee movement• Patella shifts medially in flexion and Patella shifts medially in flexion and

laterally in extensionlaterally in extension

• Failure of patella to slide,tilt,rotate,or shift Failure of patella to slide,tilt,rotate,or shift can lead to restriction of ROM,instability,or can lead to restriction of ROM,instability,or pain pain

passive mobility of patella is often passive mobility of patella is often assessed clinicallyassessed clinically

Articular surfaces:Articular surfaces:• Patellofemoral joint is the least congruent Patellofemoral joint is the least congruent

joint in the bodyjoint in the body

Articular surface of patella Femoral articular surface

Joint Congruence:Joint Congruence:• In fully extended knee patella lies on femoral In fully extended knee patella lies on femoral

sulcussulcusPatella alta – Patella alta – abnormally high position of patella on abnormally high position of patella on

femoral sulcus due to excessively long patellar femoral sulcus due to excessively long patellar tendontendon

• In extended knee patella has little or no contact wit In extended knee patella has little or no contact wit femoral sulcusfemoral sulcus

• First consistent contact of patella is made at First consistent contact of patella is made at 1010 – 20 – 20 of flexion of flexion

• Over all the range of knee flexion, medial patellar Over all the range of knee flexion, medial patellar facet normally receives the most consistent contact facet normally receives the most consistent contact with the femoral surfaces where as the odd facet with the femoral surfaces where as the odd facet receive the leastreceive the least

• Most common cartilaginous changes on Most common cartilaginous changes on patella are found on medial and odd facetspatella are found on medial and odd facets

Patella femoral Joint Reaction Force:Patella femoral Joint Reaction Force:• Patella is pulled on simultaneously by Patella is pulled on simultaneously by

quadriceps tendon superiorly and patellar quadriceps tendon superiorly and patellar tendon inferiorlytendon inferiorly

• In extension when pulls of these two are In extension when pulls of these two are vertical or in line with each other patella vertical or in line with each other patella may be suspended between them making no may be suspended between them making no contact with the femurcontact with the femur

• Even a strong contraction of quadriceps in Even a strong contraction of quadriceps in full extension will produce little or no full extension will produce little or no patellofemoral compressionpatellofemoral compression

• This is the basis for the use of SLR in This is the basis for the use of SLR in strengthening the quadriceps without increasing strengthening the quadriceps without increasing forces on the jointforces on the joint

• As flexion occurs from full extension pull of As flexion occurs from full extension pull of quadriceps(Fquadriceps(FQQ) tendon and patellar ligament (F) tendon and patellar ligament (Fplpl) ) becomes oblique compressing patella into the becomes oblique compressing patella into the femurfemur

• Compression creates a joint reaction force across Compression creates a joint reaction force across the patellofemoral jointthe patellofemoral joint

• The magnitude of The magnitude of joint reaction force (joint reaction force (R) depends R) depends upon: upon: 

a.      Magnitude of pull of quadricepsa.      Magnitude of pull of quadricepsb.      Angle of knee flexionb.      Angle of knee flexion

• Patellofemoral joint reaction force in gait Patellofemoral joint reaction force in gait when foot first contacts the ground and knee when foot first contacts the ground and knee flexes to 10flexes to 10-15-15 is 50% of body weight is 50% of body weight

• During stair case climbing and running hills During stair case climbing and running hills knee flexion goes up to 60knee flexion goes up to 60 and thus and thus increases patellofemoral joint reaction force increases patellofemoral joint reaction force to 3.3times body weight to 3.3times body weight

• Joint reaction force many reach up to Joint reaction force many reach up to 7.8times of body weight at 1307.8times of body weight at 130 of knee of knee flexion in such activities as deep knee bendsflexion in such activities as deep knee bends

• Medial facet bears the brunt of compressive Medial facet bears the brunt of compressive forcesforces

Joint stability:Joint stability:• Two stabilizing groups are present Two stabilizing groups are present • Longitudinal stabilizers - quadriceps tendon Longitudinal stabilizers - quadriceps tendon

superiorly and patellar ligament inferiorlysuperiorly and patellar ligament inferiorly• Transverse stabilizers - medial and lateral Transverse stabilizers - medial and lateral

patellar retinaculae join the vastus medialis patellar retinaculae join the vastus medialis and vastus lateralis respectivelyand vastus lateralis respectively

• Both structures help in medial-lateral Both structures help in medial-lateral positioning of patella within the femoral positioning of patella within the femoral sulcus called as ‘sulcus called as ‘Patellar Tracking’Patellar Tracking’ from from extension to flexionextension to flexion

Q (quadriceps) angle:Q (quadriceps) angle:• Defined as the angle between the quadriceps Defined as the angle between the quadriceps

muscle (primarily the rectus femoris) and the muscle (primarily the rectus femoris) and the patellar tendon and represents the angle of patellar tendon and represents the angle of quadriceps muscle forcequadriceps muscle force

• Used to clinically assess the net pull of quadriceps Used to clinically assess the net pull of quadriceps and patellar tendon and patellar tendon

• Angle formed between a line Angle formed between a line connecting ASIS to the midpoint connecting ASIS to the midpoint of patella of patella

• A line connecting the A line connecting the tibial tubercle and tibial tubercle and midpoint of patellamidpoint of patella

• Normal-men is 14° and in women is 17° Normal-men is 14° and in women is 17°

• > 20° considered to be abnormal, creating excessive lateral > 20° considered to be abnormal, creating excessive lateral forces on the patellaforces on the patella

• An increased Q angle is a risk factor for patellar subluxation An increased Q angle is a risk factor for patellar subluxation and patellar dislocationand patellar dislocation

• Anything that may increase the obliquity of the resultant Anything that may increase the obliquity of the resultant pull of the quadriceps or the obliquity of the patellar pull of the quadriceps or the obliquity of the patellar ligament may increase the lateral force on the patellaligament may increase the lateral force on the patella

• Q angle is increased in Q angle is increased in genu valgumgenu valgum increased femoral anteversionincreased femoral anteversion external tibial torsionexternal tibial torsion laterally positioned tibial tuberositylaterally positioned tibial tuberosity tight lateral retinaculumtight lateral retinaculum

Knee Injury and DiseaseKnee Injury and Disease• Injury can be due to ligaments, menisci, bones, Injury can be due to ligaments, menisci, bones,

soft tissue, bursae and tendonsoft tissue, bursae and tendon• Menisci: Medial meniscus is more injured and is Menisci: Medial meniscus is more injured and is

due to medial rotation of the femur on a fixed tibia due to medial rotation of the femur on a fixed tibia on a flexed kneeon a flexed knee

• Ligaments: Motion exceeding normal can be due Ligaments: Motion exceeding normal can be due to ligament laxity which can occur due to aging, to ligament laxity which can occur due to aging, disease, immobilization, reduced vascularitydisease, immobilization, reduced vascularity

• Bursitis: Common in prepatellar and superficial Bursitis: Common in prepatellar and superficial infrapatellar bursa (Housemaid’s Knee). This is infrapatellar bursa (Housemaid’s Knee). This is due to indirect blow/prolonged compressive stress due to indirect blow/prolonged compressive stress or areas of high frictionor areas of high friction

• PF Joint Instability: Due toPF Joint Instability: Due to

-Imbalance in Quadriceps muscle-Imbalance in Quadriceps muscle

-Tension/shortening of the lateral -Tension/shortening of the lateral retinaculumretinaculum

-Tight IT band-Tight IT band• Chondromalacia Patella: softening of Chondromalacia Patella: softening of

articular cartilage of patellaarticular cartilage of patella