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