Knee

Question 1

Distal Femur Osteology

Answer 1

Lateral/medial condyles; intercondylar notch/groove

Question 2

Tibial Articulation

Answer 2

Lateral/medial plateaus/condyles; intercondylar region

Medial is larger!

Fibula= no direct function at knee! Functions more as lateral stabilizer and attachment site for ACL

Question 3

Patella Osteology

Answer 3

Sesamoid bone, base superiorly, apex inferiorly, anterior surface convex in all directions, posterior articular surface covered with cartilage

Anterior surface is convex in all directions
Posterior surface has concavities and convexities

Question 4

Functions of Patella

Answer 4

Primary: increase angle of application (MA of quads)
Secondary: protect quads tendon from excessive friction

Question 5

Normal Alignment of the Knee

Answer 5

Shaft of the femur is slightly medial (slight genu valgum)

Angle of less than 170 degrees is excessive “knock kneed”

Angle of greater than 180 degrees is excessive “bow leg”

Question 6

Joint Capsule

Answer 6

Large, complexly attached and lax with serval recesses

Reinforced posteriorly by muscles and popliteal ligaments, M/L by collateral ligaments

VM and VL, MPFL, retinacula anteriorly

Question 7

Synovial Lining of the knee

Answer 7

Most extensive and involved in the body

Question 8

Bursa and fat pads

Answer 8

The fat pads are associated with the bursae and they reduce friction

Capsule most relaxed in slight flexion 20-25 degrees

Question 9

Menisci

Answer 9

Crescent shaped, fibrocartilaginous
Medial= semicircular
Lateral= circular
Thick peripherally and thin centrally
Blood supply is greatest in the periphery (red-red, red-white, and white-white zones)
Anterior and posterior horns anchor at the end
Secondary attachments are quads, semimembranosus, popliteus (lateral)

Question 10

Menisci Functions

Answer 10

Primary= reduce compressive stress, stabilize the joint during motion (restrict anterior and posterior translation of femoral condyles on tibia or tibia condyles on femur)

Secondary= lubricate articular cartilage, Proprioception, guide arthrokinematics

Question 11

Meniscal Movement

Answer 11

In extension, the menisci will move (more deformation in flexion)

The femoral condyles put force on the meniscus and cause it to deform outwardly

Tears in the meniscus can block of restrict movement (knees will lock if fold/tear is in the way)

Question 12

Osteokinematics of the Knee

Answer 12

2 DOF
Flex/ext in sagittal plane, and IR/ER in horizontal plane (if knee slightly flexed)

Knee will not IR/ER if the knee is extended (bony congruency in extension)

Question 13

Flexion/Extension at the Knee

Answer 13

M-L AOR; migrating AOR

Proximal on distal or distal on proximal

Question 14

Coupled Motion

Answer 14

Flex/extension do not occur as pure sagittal plane motions–axis oblique
TIbia moves from position of slightly lateral to femur to slightly medial to femur in full flexion

Question 15

ER/IR

Answer 15

“Axial rotation,” longitudinal/vertical AOR
–increases with knee flexion
90 degrees of flexion yields 40-45 degrees of rot;
ER when tibial tuberosity is lateral to anterior distal femur

Question 16

Arthrokinematics- Extension

Answer 16

Tibia on femur–>tibia rolls and glides anteriorly

Femur on Tiba–>femoral condyles roll anteriorly ad glide posteriorly

Question 17

Arthrokinematics- Flexion

Answer 17

Tibia must 1st IR to “unlock” (popliteus)
Tibia on femur–>popliteus initiates tibial IR
Femur on tibia–>popliteus initiates femoral ER

Question 18

Scream Home (locking) Mechanism

Answer 18

Obligatory ER of tibia during terminal knee extension (TKE)
–not voluntary or produced by muscular forces
Joint arthrology dictates arthrokinematics during the final 30 degrees of KE
Flexion force “unlocks” by medially rotating the tibia
—in femur-on-tibia movement, the femur will externally rotate

Question 19

Collateral Ligaments

Answer 19

Provide frontal plane stability against varus/valgus force

-MCL and LCL

Question 20

Cruciate Ligaments

Answer 20

Provide multi planar stability at knee

-ACL and PCL

Question 21

MCL

Answer 21

Resists valgus stresses (reinforces capsule)
At full extension, 57% of restraining force
At 25 degrees of flexion, 78% of restraining force
(So, provides more force when the knee if flexed)
–2 degree role in preventing anterior translation—may place stress on ACL if injured
Vascularized, so has capacity to heal

Question 22

LCL

Answer 22

Resists Varus stresses
At 5 degrees of flexion accounts for 55% of restraining force
At 25 degrees flexion accounts for 69% of restraining force

Question 23

Cruciate ligaments function

Answer 23

Names for their attachment to the tibia
Together provide multiplane stability of the knee, mostly in sagittal plane
Guide arthrokinematics
Contribute to Proprioception

Question 24

ACL

Answer 24

Runs from anterior tibial plateau to lateral femoral condyle
Primary restraint to anterior displacement of tibia on femoral condyles
Two bands wrap around each other–AMB and PLB
Most fibers taut with knee close to full extension

Question 25

ACL Injury

Answer 25

Most commonly injured when knee is slightly flexed and tibia is rotated in either direction (non-contact or contact)
Forceful contraction of the quads pulls tibia anteriorly, so can strain ACL especially near full extension

Question 26

PCL Function

Answer 26

Runs from posterior intercondylar area of tibia to medial femoral condyle
1 degree restraint to posterior displacement of the tibia on femoral condyles (or anterior displacement of femur on tibia in closed chain)
Has two bands PMB and ALB

Question 27

PCL Injury

Answer 27

Majority of fibers remain taut throughout flexion/extension but most taut with greater flexion
Contraction of hamstring can slide tib/fib posterior, PCL can check the posterior translation
Most injuries are TRAUMATIC

Question 28

Patellafemoral Joint

Answer 28

Interface between patella and intercondylar groove
As knee flexes and extends, slides over the intercondylar groove
Max contact only 30% of total surface area

Question 29

What happens are patella-femoral moves from flexion to extension?

Answer 29

Contact of patella moves from superior (base) to inferior (apex)

Question 30

Q-Angele

Answer 30

ASIS to mid-patella–tibial tuberosity to mid-patella

Approx 15 degrees in women and 11 degrees in men

Greater than 15 degrees is considered abnormal

Question 31

Medial Directed Forces at Patella

Answer 31

Vastus Medialis Oblique, raised lateral facet of intercondylar groove, medial patellar retinacular fibers

Question 32

Lateral Directed Forces of Patella

Answer 32

ITB, lateral patellar reitnacular fibers, bow stringing force

Question 33

Extensors

Answer 33

Quadriceps

Efficiency created by patella, creates 2/3 greater force than hamstrings, maximal torque at mid range (40-70 degrees of flexion)
Dampens impact of loading
Accelerate the tibia or femur for tasks requiring knee extension
Quads responsible for shock absorption

Question 34

Tibia on Femoral motion–moment arm

Answer 34

External moment arm increases as it gets into extended position (so more difficult to extend knee as you reach full extension)

Question 35

Femoral on Tibia motion–moment arm

Answer 35

External moment arm decreases from flexion to extension (so easier to stand up from mini-squat)

Question 36

Moment arm at 45 degrees of flexion?

Answer 36

Tibia-on-femur and femur-on-tibia motion–>moment arm is equal at 45 degrees (same amount of difficulty in tasks at 45 degrees)

Think about squats vs. quad sets

Question 37

Flexors/Rotators–Hamstrings

Answer 37

Most active during walking/running
Accelerate or decelerate the tibia during tibia on femoral movements; Stabilize in femur on tibia movements

Maximal torque development near full knee extension

Question 38

Flexors/Rotators–Sartorius/Gracilis

Answer 38

Pes anserine provides medial stability and functions to IR tibia

Question 39

Flexors/Rotators–Popliteus

Answer 39

IR and flexor; “unlocks” the knee