knee

Question 1

what is the mechanical axis also known as?

Answer 1

weightbearing line

Question 2

what is the mechanical axis

Answer 2

a weightbearing line that is drawn from the middle of the calcaneus to the head of the femur

Question 3

where should the weightbearing line pass through?

Answer 3

knee joint center

Question 4

tibiofemoral alignment

what is the normal angulation of femur?

Answer 4

femur is 5° off of vertical = 185°

Question 5

tibiofemoral alignment - knee

what is the genu valgum degree?

Answer 5

> 185°

bigger angle!!

Question 6

tibiofemoral alignment -knee

what is genu varum degree?

Answer 6

≤ 175°

smaller angle

Question 7

knee

what are the functions of the menisci?

Answer 7

• shock absorption (50-70% WB –> redistrubutes back)
• increased congruence of the joint (stability)
• lubricates the joint (reduce friction) –> fluid filled barrier
• provides proprioception

Question 8

knee

what are the zones of vascularization in the meniscus?

Answer 8

red zone: 25% of meniscus
pink zone: 25%-33% of meniscus
white zone: 33%-50% of meniscus

as an adult

Question 9

knee

what zone of the meniscus takes the most load, and takes the load first?

Answer 9

white zone

Question 10

knee

mensical tears can be?

Answer 10

acute or chronic

Question 11

knee

what makes a meniscal tear acute? chronic?

Answer 11

acute - often a twisting and loading component
chronic - older patietnes

Question 12

knee

what are symptoms of a meniscal tear?

Answer 12

• popping, locking
• giving way
• pain with activites (e.g. stair climbing)
• pain and tenderness with palpation at the joint line
• effusion (swelling) –> intracapsular so local to knee
• difficulties with full extension
• pain with full flexion or limited ROM
• antalgic gait

Question 13

knee

where does the ACL orignate and attach?

Answer 13

originate: posteriomedial aspect of the lateral femoral condyle
attach: tibia on the lateral and anterior aspect of the medial intercondylar tibial spine

Question 14

knee

Ground reaction force vector (GRFV) is the sum of what?

Answer 14

2 or 3 directions

Question 15

knee

what is needed for the ground reaction force to be calculated?

Answer 15

first the body is seperated into two masses: knee down and the rest of body
3 things needed:
- contact time - heel on ground
- limb was in air (body in air -aerial time)
- limb acceleration –> determines GRF

Question 16

knee

does the lateral or medial meniscus have more artiuclar cartilage? why?

Answer 16

lateral meniscus has more articular cartilge becasue it moves more A and P than medial

Question 17

knee

the medial meniscus and medial collateral ligament have an attachment but the lateral does not. what does this attachment do?

Answer 17

aides in stability

Question 18

knee

what orthopedic procedure is the most common in the US for meniscus?

Answer 18

partial medial menisectomy

Question 19

knee

what is the structure of the ACL from its origin to attachment site?

Answer 19

twists laterally as it travels distally

Question 20

knee

what are the 2 bundles of the ACL?

Answer 20

anteromedial bundle (AMB)
posterolateral bundle (PLB)

bundles - think tibial insertions

Question 21

knee

when is the anteromedial bundle slack?

Answer 21

in extension

Question 22

knee

when is the posterolateral bundle of ACL slack?

Answer 22

in flexion

Question 23

knee

the ACL remains fairly taut throught knee range of motion. what degree range is the ACL as a whole the most taut?

Answer 23

15°-30° of knee flexion

Question 24

knee

although the ACL remains failry taut throughout knee ROM when is the ACL least taut?

Answer 24

30°-60° of knee flexion

Question 25

# knee is the ACL intracapsular or extracapsular?

Answer 25

intracapsualr

Question 26

# knee ACL - list the function

Answer 26

important stabilizer of the knee joint especially in the sagittal plane

Question 27

# knee ACL function - most fibers of the ACL resist extension by resisting:

Answer 27

- excessive anterior tibial translation - posterior translation of the femur - or a combo of both - resists extreme varus, valgus and axial rotation ## Footnote * the anterior/posterior translation matters arthrokinematiclly but not for the sake of ligament

Question 28

# knee ACL - injury mechanisms plant and cut:

Answer 28

one legged landing, often in combination with: - large valgus producting force - large axial rotation torque - knee close to full extension (opp, already alot of load) severe hyperextension of the knee

Question 29

# knee PCL - function: origin and insertion

Answer 29

orignates: lateral aspect of the medial femoral condyle attaches: posterior tibial surface, between the posterior horns of the two menisci

Question 30

# knee PCL - structure

Answer 30

greater cross-sectional area than the ACL

Question 31

# knee PCL - two bundles | think tibial insertions

Answer 31

Anterolateral Bundle (ALB) Posteromedial bundle (PMB) ## Footnote inbetween flexion/extension both taut

Question 32

# knee how much bigger is the PCL compared to ACL?

Answer 32

150%

Question 33

# knee PCL - resists knee flexion. is also primary restraint for what? also resists what?

Answer 33

primary restraint for posterior translation of the tibia - also resists anterior translation of the femur and the combination of both - resists extreme varus, valgus and axial rotation

Question 34

# knee PCL - injury mechanims

Answer 34

- forceful posterior translation of the tibia/anterior translation of the femur while knee is flexed - large axial rotation or valgus-varus force with foot planted and knee in flexion - falling on fully flexed knee with ankle fully plantar flexed - severe hyperextension of the knee

Question 35

# knee what is a dashboard injury?

Answer 35

PCL injury - forceful posterior translation of the tibia/anteror translation of the femur while knee is flexed

Question 36

# knee what works against and unloads PCL?

Answer 36

quadriceps

Question 37

# knee what increases load on PCL? ## Footnote when you unload ACL you load PCL -there is a balance

Answer 37

hamstring, gastrocnemius

Question 38

# knee MCL function - superficial fibers

Answer 38

- arise from the medial femoral epicondyle - insert into the medial aspect of proximal tibia

Question 39

# knee MCL function - deep fibers

Answer 39

- arise from the inferior aspect of the medial femoral epicondyle - inserst into the posterior-medial joint capsule, medial meniscus, and tendon of the semimembranosus

Question 40

# knee the MCL has a rich blood supply which means the MCL has?

Answer 40

a good capacity to heal

Question 41

# knee MCL function - resists what 2 motions?

Answer 41

- resists knee valgus (abduction) and knee external rotation - secondary role in resisting anterior translation of the tibia

Question 42

# knee the MCL tearing will significanlty increase what?

Answer 42

ACL load

Question 43

# knee MCL injury mechanisms -

Answer 43

- valgus producing force with the foot planted - severe hyperextension of the knee

Question 44

# knee is the LCL intra or extra capsular? why?

Answer 44

extracapsular - does not attach to lateral meniscus

Question 45

# knee LCL origination and attachment?

Answer 45

arises at lateral femoral epicondyle inserts into fibular head (conjoined tendon with the biceps femoris)

Question 46

# knee LCL blood supply?

Answer 46

has good blood supply but does not heal as quickly as the MCL

Question 47

# knee LCL function?

Answer 47

resists knee varus (adduction), knee extension and internal rotation (to lesser degree external rotation too) ## Footnote primary varus stabilizer of the knee

Question 48

# knee LCL- injury mechanisms

Answer 48

- varus prodcuing force with the foot planted - severe hyperextension of the knee

Question 49

# knee acl reconstruction is often misdiagnosed due to what?

Answer 49

due to x rays beingtaken to see if there is a fracture. 1 of 3 experience subsequent rupture after ACL reconstruction