knee (L8)

explain screw home mechanism for open chain vs closed chain

-OC knee extension: concave tibia rolls and glides anteriorly on the stationary convex femur (during last 30 degrees of knee extension, there is ER of tibia) -CC knee extension: convex femur rolls anterior and slides posteriorly on the stationary concave tibia (during last 30 degrees of extension, there is IR of femur)

explain the different body mechanics that will increase or decrease stress on the ACL as you land from a jump

-more likely for ACL injury: more upright = places higher demand on quadriceps (creates longer moment arm for quadriceps) (this causes more energy to be absorbed by knee joint) -less likely for ACL injury: more flexion at trunk = longer moment arm at hip joint, so hip joint can share absorbing energy with knee (keeps knee from taking brunt of energy absorption)

what 3 structures are involved in the unhappy triad?

1. anterior cruciate ligament 2. medial meniscus 3. medial collateral ligament

Anterior Cruciate Ligament (ACL) proximal and distal attachment

1. proximal end: attaches in lateral, posterior and superior direction 2. distal end: attaches to anterior intercondylar

Common Mechanism of Injury: ACL Factors associated with a non-contact ACL injury 1. strong activation of the ____________ muscle over a moderately _________ or nearly _________ knee 2. a marked "__________ collapse" of the knee (dynamic Q-angle) 3.excessive ______________ __________ of the knee (i.e., the femur excessively rotated____________ at the hip relative to a fixed tibia) so may attribute to reduced activation of hip ___________ and_______________________ (gluteus maximus)

1. quadricep/flexed/extended 2. valgus 3. external rotation/ internally/abductor/external rot

what are the 3 contributing factors to screw home mechanism?

1. shape of medial femoral condyle 2. tension in anterior cruciate ligament 3. lateral pull of quadriceps

Screw-home Mechanism: Tibia-on-femur Extension (open chain) For an open chain knee extension, _____° external rotation of the tibia during the last _____ ° of extension

10 30

Screw Home Mechanism: Femur-on-tibia Extension (Closed Chain) (tibia is FIXED) •Full knee extension requires ____° femoral ____ •__________ femoral condyle completes rolling, gliding motion at ~_____° flexion •As extension continues, ________ condyle continues to glide, roll •Results in __________ rotation of femur on tibia •The knee joint is now "_______"

10/IR lateral/30 medial internal locked

Frontal Plane Anatomical Alignment •Normal alignment: _____°-______° •Abnormal alignment: 1. Excessive genu valgum (knock-knee) <_______° 2. Genu varum (bow-leg) >________°

170°-175° 165 180

Tibiofemoral Joint Osteokinematics •______ Degrees of Freedom (DOF) what 2 movements occur?

2 •Extension/Flexion •Internal/External Rotation

Meniscal Resection and Contact Area •Removal of menisci decrease contact area by a factor of ____ to ____ ↑ Stress (Load per unit area) •Leads to ___________________ and then to ________________

3-5 cartilage degeneration Osteoarthritis

________ to __________ degrees offers a high challenge for quadriceps

45-0 degrees leg extension (open chain) 45-90 degrees squat (closed chain)

Common Mechanism of Injury: ACL •____ % non-contact injury •Many occur while landing from a jump, quickly and forcefully changing direction, decelerating, cutting or pivoting over a single planted lower limb

70

Maximun torque generation when the knee joint angle in between ________ and _______ degrees of flexion why?

80 and 30 because of the length-tension relationship (therefore will be affected by hip joint angle)

Posterior drawer test: Posterior pushing force with knee flexion at ______ °

90

Tibiofemoral Joint Osteokinematics: Internal/External Rotation •max range of IR/ER occurs at _______° flexion •______-____° total •ER:IR = ___:____

90 40-50 2:1

During a weight bearing movement, from 90 to 0 degrees of knee flexion, which knee position has largest external torque demand? Why?

90 degrees because it has the largest external moment arm

_________ to ________ degrees offers a low challenge to quadriceps

90-45 degrees leg extension (open chain) 0-45 degrees squat (closed chain)

Anterior Cruciate Ligament (ACL) resists: •___________ (primary) - Anterior translation of the_______ - Posterior translation of the _______ - Combination of both •____________ and __________ stress • ________ rotation

Extension tibia femur Valgus/varus Axial

Name the extracapsular ligaments of the knee and the intracapsular ligaments?

Extracapsular Ligaments •Medial Collateral Ligament (MCL) •Lateral Collateral Ligament (LCL) Intracapsular Ligaments •Anterior Cruciate Ligament (ACL) •Posterior Cruciate Ligament (PCL)

Meniscal Movement during Knee Flexion/Extension Closed chain (weight-bearing), menisci follow Roll motion of ___________ •During extension, femur Rolls _____________ Thus, menisci move ____________. •During flexion, femur Rolls ____________. Thus, menisci move ____________.

FEMUR anteriorly anteriorly posteriorly posteriorly

Posterior Cruciate Ligament (PCL) Resists: •_________ - Posterior translation of the ________ - Anterior translation of the ________ - Combination of both •__________ and ________ stress •_________________

Flexion tibia femur Valgus/varus Axial rotation

During a non-weight bearing movement, from 90 to 0 degrees of knee flexion, which knee position has largest external torque demand? Why?

Full extension (0 degrees), because it has the longest external moment arm (perpendicular distance from the line of force (gravity) to the axis of rotation)

The Menisci •External border of the lateral meniscus does NOT attach to _______ (only attachs to ________________)

LCL joint capsule

Anterior Cruciate Ligament (ACL) •2 portions: which is smaller and which is larger?

Larger posterior-lateral Smaller anterior-medial

Bony Morphology: Patella •___________ facet >___________ facet •The thick cartilage (up to 4-5 mm) helps to disperse the large __________________ force across the patellofemoral joint

Lateral>medial compression

Patellofemoral Kinematics - Path (Patellar Tracking) •______________ or ___________- shift (≈ 3 mm) •From extension to flexion: first shift ____________(≈ 30° flexion) then ___________ (≈ 90° flexion) •Excessive lateral shift has been observed in people with___________ knee pain

Medial or lateral medially laterally anterior

Most ______ injuries are associated with high-energy trauma (automobile accident)

PCL

how to calculate PFJ stress?

PFJ Force/Contact Area

The Menisci Muscle attachements (secondary) (3 muscles)

Quadriceps, semimembranosus and popliteus

Meniscal Movement during Knee Flexion/Extension Open chain (non-weight-bearing), menisci follow Roll motion of _____________- •During extension, menisci move ____________ since tibia rolls ____________ •During flexion, menisci move ____________ since tibia rolls____________

TIBIA anteriorly/anteriorly posteriorly posteriorly

Medial Collateral Ligament Resists forces in what direction? •___________ stress (primary) •______________________ •________________________

Valgus Medial/Lateral rotation Full extension (posterior portion)

what would make the anterior drawer test for ACL tear invalid?

a hamstring spasm

What force direction does the quadriceps produce during knee extension? Anterior or Posterior? How does this affect the ACL?

anterior ACL is taut

•Cruciate Ligaments (ACL, PCL) function: •Primary: ________/_______ stability •Secondary: ________/_______ stability •____________ stability

anterior/posterior medial/lateral Rotatory

EXTENSION femur on tibia is (open or closed) chain the tibia is (fixed/mobile) the femur rolls (ant/post) and slides (ant/post) and (external/internal) rotation the menisci moves (ant/post)

closed fixed ant post internal ant

Function of the Menisci: •Guide knee arthrokinematics (_________) •Contribute to joint __________ •Provide _________________

concave stability proprioception

Function of the menisci: Increase ________ area by: •Reduce stress (force/area) on _______ _________ •Enhance _____________ of the tibiofemoral joint •Distribute________ ________ force

contact articular cartilage congruence weight bearing

common MOI for MCL?

contact injury force applied to lateral side of knee

Medial Collateral Ligament Posterior portion: • (Superficial/Deep) •Extends (less/farther) distally •Attaches to......... (3)

deep less to tibial condyle, capsule, medial meniscus

Compare the joint compression force on the patellofemoral joint of a partial squat and a deep squat, which one is larger?

deep squat

the femoral condyles have greater joint congruency in ________________

extension

what is the close-packed position of tibiofemoral joint?

extension

how much extension occurs at the tibiofemoral joint? how much flexion occurs at the tibiofemoral joint?

extension: 5 degrees flexion: 140 degrees

what is the closed packed positon of the tibiofemoral joint?

extention

Cruciate Ligaments: Anterior and Posterior •Resist ________________ of knee motion •Guide ________________ •Posterior compared to Anterior •_______________ •________________

extremes arthrokinematics posterior is Stronger posterior has larger CSA

Collateral Ligaments: Medial and Lateral •Reinforce ____________ capsule of the knee joint •Function - Primary : prevent excessive ___________ plane motion •__________ and _____________ •Contribution greatest as knee___________ ~30° - Secondary : •Resist ___________________ •Resist ___________________

fibrous frontal Valgus, varus flexes hyperextension axial rotation

Periarticular Connective Tissues Joint capsule and reinforcing ligaments •The ___________ capsule encloses both the __________________ joint and the ________________ joint (dotted line) •The capsule is reinforced by........

fibrous tibiofemoral patellofemoral muscles, ligament and fascia

Screw Home Mechanism:Femur-on-tibia Extension (Closed Chain) (tibia is FIXED) •Popliteus: causing ____________ and ________________ of the femur, to "________ "the knee

flexion lateral rotation unlock

stress = __________/_________ this means that a removal of menisci increases the ________ on the cartilage in the knee, which causes the cartilage to ___________ much faster

force/area stress degenerate

what is the close packed position of the knee?

full extension

The Menisci: Blood Supply •The peripheral 1/3 of the menisci receives a direct source of blood from ______________ arteries (branches of the popliteal artery) •The inner 2/3 of the menisci is essentially ______________, receives nourishment only from _________ fluid

genicular avascular synovial

What is the agonist of the ACL? why?

hamstring because a contraction of the hamstring protects the ACL by making the ACL less taut

•Antagonist of PCL: _________________ (especially at around ______° knee ________________)

hamstring 90 flexion

Patella Motion: 6 Degrees of Freedom

in pic

The Menisci •Anchored to the ________________ region of the tibia by their anterior and posterior horns •External border of the medial meniscus attaches to____________

intercondylar MCL

What is the common MOI of the unhappy knee triad? (ACL, MCL, medial meniscus)

knee valgus and ER

the medial femoral condyle is _______ than the lateral condyle

larger

Increased Q-angle, increased __________ pull on the patella

lateral

Bony Morphology: Trochlea Groove Higher raised ___________ facet so steeper ___________ side

lateral lateral

does using the hamstring along with the quad make the ACL have more or less tension?

less

Disparity Between Medial and Lateral Femoral Articular Surfaces •Articular surface: __________ > ___________ •Pure _________ plane motion fails to use entire articular surface •Requires motion (rotation) in ____________ plane to use articular surface

medial > lateral sagittal transverse

Posterior Cruciate Ligament (PCL) •Orientation of PCL: From distal end to proximal: ___________,__________,____________ •2 portions: •Larger __________ set •Smaller ____________ set

medial, anterior, superior anterior posterior

Collateral Ligaments (MCL, LCL) function: •Primary: ________/_______ stability •Secondary: ________/_______ stability •____________ stability

medial/lateral anterior/posterior Rotatory

Different size and shape in the medial and lateral condyles of femur Size: ____________ condyle > ____________ condyle •_________________ condyle extends farther anteriorly and curves about _____°

medial>lateral medial 30 degrees

EXTENSION Tibia on femur is (open or closed) chain? the femur is (fixed/mobile) the tibia rolls (ant/post) and slides (ant/post) and (external/internal) rotation the menisci moves (ant/post)

open fixed ant ant external ant

Bony Morphology: Trochlea Groove Articulate with the ______________ (larger lateral facet)

patella

what is the largest sesamoid bone in the body?

patella

Bony Morphology: Trochlea Groove Larger sulcus angle (shallower groove) at the more ___________ end

proximal

the Q angle describes the line of pull of the ___________

quadriceps

what is the antagonist of ACL?

quadriceps

2 Factors Associated with Joint Compression Force on the Patellofemoral Joint 1. Force generated by the _____________ muscles (related to the external torque demand) 2. Knee flexion angle •__________ resultant force at larger flexion angle •__________ external torque demand at larger flexion angle

quadriceps Larger Larger

Patellofemoral Joint: Local Stabilizers •_______________ muscle •The fit of the _________ surfaces •Passive_______________ from the surrounding soft tissues (ligaments, tendons, retinaculums)

quadriceps muscle articular restraint

there is variation in curvature of femoral condyles in ______________ plane the posterior femoral condyle has a tighter ________, so it has a ________ radius the lateral femoral condyle has a less tight curvature, so it has a _________ radius

sagittal curvature; smaller larger

Effects of the Quadriceps Muscle Acting on the Patellofemoral Joint: •Creates compression force (__________ plane) •Provide dynamic patellar _________

sagittal stability

Bony Morphology: Trochlea Groove the larger the sulcus angle, the more _______ the groove

shallow

Bony Morphology: Trochlea Groove the medial side is more ________

shallow

Decreased patellofemoral joint stability when the patella locates at ________________ trochlea groove

shallower trochlea

if we remove patella, it makes the internal moment arm _________ for the __________ and ________ ______ ________

shorter quadriceps patellar femoral tendon

Bony Morphology: Tibia •Articular surfaces ______________ than those on femur •articular surface:____________ tibial condyle > ____________

smaller medial> lateral

Patellofemoral Joint •The patella functions as a "__________" between femur and quadriceps ----> increases internal moment arm of____________

spacer quadriceps

Medial Collateral Ligament Anterior portion: • (Superficial/Deep) •Extends (less/farther) distally •Attaches to......... (1)

superficial further medial tibial shaft

knee flexion = contact area on PATELLA is more ________ knee extension = contact area on PATELLA is more _________ at ________ degrees, the sides of the patella make contact with the trochlear groove

superior inferior 135

Patella Contact Areas at Different Knee Flexion Angles •As the knee extends, the contact point on the patella migrates from its ______________ pole to its _____________ pole. •↑ contact area with knee __________

superior inferior flexion picture depicts knee flexion angles and contact area of patella

Quadriceps is the prime mover of the patella, it pulls the patella into what 3 directions?

superior lateral posterior

Patellofemoral Kinematics - Path (Patellar Tracking) •Patella move _____________ during extension, _____________ during flexion (open chain) •Full extension: Patella rests completely ________________ to the trochlear groove

superiorly inferiorly proximal

Periarticular Connective Tissues •The ______________ membrane lies in the internal surface of the joint capsule •____________ and ___________ form at inter-tissue junctions that encounter friction during movement (ligament and tendon, muscle and capsule, bone and skin, tendon and bone, bone and muscle, bone and ligament)

synovial Bursae and fat pads

Explain the basic concept of the screw-home Mechanism

there is external rotation involved in open chain knee extension to achieve knees most stable position

Closed-chain movement of patella: Patella stays relatively in place (because ________ is fixed on the ground)

tibia

Patella follows movement of ____________ (patellar tendon is non-contractile)

tibia

ER of knee occurs because of either ER of _______ (open chain) or IR of ________ (closed chain)

tibia femur

Patellofemoral Joint is the interface between the articular side of the patella and the ______________ _____________ of the femur

trochlear groove

Open chain movement of patella: During tibial-on-femoral movements, the patella slides relative to the fixed what?

trochlear groove of the femur

landing more upright causes more knee _________

valgus

what accessory motions occur at the tibiofemoral joint?

valgus/varus

talk about the force of the quadriceps and length of the ACL at 80 degrees of knee flexion

when the knee is flexed 80 degrees, the quadriceps has no anterior force acting n the tibia, which doesnt make the ACL taut

Lateral Collateral Ligament Attachments (1)

•Head of fibula •NO attachments to meniscus or capsule

Cruciate Ligaments: Anterior and Posterior •Provide stability in multiple directions what is the primary and secondary?

•Primary: anterio-posterior forces •Secondary: rotational, frontal plane stresses

Lateral Collateral Ligament •Resists ___________ stress (primary) ______________________ ________________________

•Varus stress (primary) •Medial/Lateral rotation •Full Extension