ANATOMY OF THE ANATOMY OF THE KNEE JOINTKNEE JOINT

Fahad zakwanFahad zakwan

MD5MD5

Knee JointKnee Joint• actually 2 joints within actually 2 joints within the articular capsulethe articular capsule• tibio-femoraltibio-femoral• patello-femoralpatello-femoral• the the superior fibulo-tibial superior fibulo-tibial jointjoint is also near is also near

•modified hinge jointmodified hinge joint• flexionflexion and and extensionextension is is primary motionprimary motion• some rotation is possible some rotation is possible when the knee is flexedwhen the knee is flexed

AnteriorAnterior PosteriorPosterior AnteriorAnteriorTransverseTransverse

condylesepicondylesepicondyles

intercondylar intercondylar notchnotch

patellapatella

tibial tuberositytibial tuberosity

tibial plateaustibial plateaus

Ligamentous SupportLigamentous Support

MeniscMeniscii

CollateralCollateralLigamentLigament

ss

CruciateCruciateLigamentsLigaments

Other Other LigamenLigamen

tsts

MenisciMenisci

• The menisci are The menisci are discs of fibrocartilage discs of fibrocartilage attached to tibial attached to tibial plateaus. They are thicker along the periphery.plateaus. They are thicker along the periphery.

The lateral The lateral meniscusmeniscus is is smaller and more smaller and more mobile than the mobile than the medial meniscus. medial meniscus. The inner portion of The inner portion of the menisci are the menisci are avascular. The avascular. The outer portion has outer portion has some blood supply, some blood supply, making healing of making healing of tears possible.tears possible.

lateralaterall

mediamediall

Menisci FunctionMenisci Function• increases stability increases stability by by deepening tibial plateausdeepening tibial plateaus• decreases friction decreases friction by 20%by 20%• increases contact areaincreases contact area by 70%by 70%• absorbs shockabsorbs shock• removal of menisci does NOT removal of menisci does NOT

preclude normal motion, butpreclude normal motion, but• increase wear on articulating increase wear on articulating

surfaces surfaces • increase chance of developing increase chance of developing

degenerative joint diseasedegenerative joint disease

lateral (fibular)

medial (tibial)

Collateral Collateral LigamentsLigaments

prevents prevents abduction abduction

and and adduction adduction movement movement of the kneeof the knee

Collateral Collateral LigamentsLigaments

Additional Ligamentous

Support

•iliotibial bandthick, strong band of tissue connecting tensor fascia latae to femur and tibia

Cruciate Cruciate LLigamentsigamentscruciate -- ‘cross’ cruciate -- ‘cross’

•ligaments form an ‘X’ or ligaments form an ‘X’ or cross within the jointcross within the joint•named for their TIBIAL named for their TIBIAL attachmentsattachments

Posterior Crucuate (PCL)Posterior Crucuate (PCL)

shorter and stronger thanshorter and stronger thanACLACL

FFEEMMUURR

TIBIA

PATELLA

The The ACLACL prevents the prevents the femur from sliding femur from sliding posteriorly on the tibia posteriorly on the tibia or the tibia from or the tibia from sliding anteriorly on sliding anteriorly on the femur.the femur.

The The PCLPCL prevents prevents the femur from the femur from sliding anteriorly on sliding anteriorly on the tibia or the tibia the tibia or the tibia from sliding from sliding posteriorly on the posteriorly on the femurfemur.

Cruciates During Cruciates During Flexion/ExtensionFlexion/Extension

Note: the Note: the cruciate cruciate ligaments ligaments also limit also limit rotationrotation

Patello-femoral Joint Patello-femoral Joint

• articulation of the articulation of the patella and femurpatella and femur• the patella is a true the patella is a true sesamoid bonesesamoid bone• posterior surface of the posterior surface of the patella is covered with patella is covered with thick hyaline cartilagethick hyaline cartilage• the patella slides within the patella slides within the trochlear groovethe trochlear groove

Functions of Patello-femoral Functions of Patello-femoral JointJoint

(1) (1) increases angle of pull of increases angle of pull of quads on tibiaquads on tibia, improves , improves the ratio of the ratio of motive:resistive torque by motive:resistive torque by 50%50%

(2) centralizes divergent (2) centralizes divergent tension of quads into a tension of quads into a single line of actionsingle line of action

(3) some (3) some protectionprotection of of anterior aspect of kneeanterior aspect of knee

without patellawith patella

Q-AngleQ-AngleThe Q-angle is the angle The Q-angle is the angle formed by a line from the formed by a line from the anterior superior spine of anterior superior spine of the ilium to the middle of the ilium to the middle of the patella and a line from the patella and a line from the middle of the patella to the middle of the patella to the tibial tuberosity. the tibial tuberosity. MalesMales typically have Q-angles typically have Q-angles between between 10 to 1410 to 14oo, , femalesfemales between between 15-1715-17oo..

Atypical Q-anglesAtypical Q-angles

Knee RotationKnee Rotation(Locking Your Knee)(Locking Your Knee)

• Six to 30 degrees of internal Six to 30 degrees of internal rotation of the tibia on the rotation of the tibia on the femur occurs through 90 femur occurs through 90 degrees of knee flexion.degrees of knee flexion.

1 The femoral condyles do not have the same diameters, The femoral condyles do not have the same diameters, this helps cause internal rotation when the knee is flexed this helps cause internal rotation when the knee is flexed and external rotation when the knee is extended.and external rotation when the knee is extended.

2 The lateral condyle slides more than medial condyle.The lateral condyle slides more than medial condyle.3 The anterior cruciate ligament becomes taut just prior to The anterior cruciate ligament becomes taut just prior to

the rotation, this may help force a rotation of the femur on the rotation, this may help force a rotation of the femur on the tibia.the tibia.

FlexionExternalRotation

InternalRotation

Extension

Knee Knee MusculatureMusculature

many are 2 joint muscles

primary movements - flexion and extension - hams & quads, respectively

medial and lateral rotation possible necessary for screw-home mechanism

Knee FlexionKnee FlexionHamstringsHamstrings cross hip cross hip andand knee knee

1.1. biceps femorisbiceps femoris

2.2. semitendinosussemitendinosus

3.3. semimembranosussemimembranosus

gastrocnemiusgastrocnemius cross knee cross knee andand ankle ankle

popliteus

1. rectus femorisrectus femoris

2.2. Vastus lateralisVastus lateralis

3.3. Vastus medialisVastus medialis

4.4. Vastus intermediusVastus intermedius

quadriceps tendonquadriceps tendon

patellar ligamentpatellar ligament

Knee Extension - Knee Extension - QuadricepsQuadriceps

Lateral RotationLateral Rotationbiceps femorisbiceps femoris attaches to lateral aspect of kneeattaches to lateral aspect of knee

Medial RotationMedial Rotation

semitendinosussemitendinosus

semimembranosussemimembranosus

popliteuspopliteus

attach to medial aspect of kneeattach to medial aspect of knee

Vascular Vascular AnatomyAnatomy

•Popliteal artery Popliteal artery at at risk for being tethered risk for being tethered • If blood flow through If blood flow through popliteal artery popliteal artery disrupted disrupted Inadequate blood Inadequate blood supply distallysupply distally

Anatomy: Anatomy: NervesNerves• Peroneal nervePeroneal nerve• More commonly injuredMore commonly injured• Tethered around the fibular Tethered around the fibular

neckneck• Mechanism of injuryMechanism of injury

• Tension (Varus ± hyperextension, Tension (Varus ± hyperextension, Translation (Anterior /Posterior Translation (Anterior /Posterior dislocation)dislocation)

• Direct impactDirect impact• Iatrogenic (aggressive Iatrogenic (aggressive

varus/hyperextension during EUA varus/hyperextension during EUA (!)(!)

• Tibial nerveTibial nerve