Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Unit 2 > 10-14b Knee Biomechanics I > Flashcards

10-14b Knee Biomechanics I Flashcards

1
Q

Why is the tibiofemoral joint so commonly injured?

A

Lots of sagittal plane motion (not as much transversal/frontal plane motion)

Lots of force (longest bones in the body = lots of force); if they go in the opposite directions = bad

Above and below: the knee is the symptom to hip, ankle, and foot motion. Caught in between more mobile joints

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are the two articulations of the tibiofemoral joint?

A

medial femoral condyle articulating with the medial tibial plateau

lateral femoral condyle articulating with the lateral tibial plateau

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Which condyle on the femur projects more distally?

A

medial condyle by about 2/3 of an inch

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Where do the cruciate ligaments attach?

A

intercondylar fossa

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What does the patella engage with on the femur during early flexion?

A

trochlear groove

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

In which plane are the femoral condyles more convex? Frontal or sagittal?

A

Sagittal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How do the tibial condyles project in the frontal plane?

A

slightly concave

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How do the tibial condyles project in the sagittal plane?

A

medial: slightly concave
lateral: slightly convex

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Which condyle has a longer anterior-posterior length?

A

medial condyle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What attaches at the intercondylar tubercles?

A

cruciate ligaments

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What fills the joint space of the tibiofemoral joint?

A

hyaline cartilage

meniscus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

How does the medial meniscus compare to the lateral meniscus shape-wise?

A

medial meniscus: C shape

lateral meniscus: circular O shape

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How does the meniscus help the articulation of the femur and tibia?

A

gives the femur a concave shape to rest in

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are the primary functions of the menisci?

A

Enhance TF congruency: distribution of forces by increasing the contact area to absorb 40-60% of the normal load: shock absorbers

help with friction/shear reduction

provide joint stability

assist in lubrication of the joint: hyaline cartilage has poor joint supply, so another structure forces more synovial fluid against the hyaline cartilage and provides more nutrients

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What are the secondary directions in which the meniscus stabilizes?

A

restrains movement in A/P directions

and with combined valgus and rotation by providing stability

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are the implications of a menisectomy?

A

contact area decreases and adds stress to the femur (Stress = Force/Contact Area)

long-term consequences are arthritis (14 times more likely for OA w/ menisectomy)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Describe Meniscal mobility. Which one is more mobile? How does weight-bearing affect mobility?

A

Medial meniscus is more restricted due to greater ligamentous/capsular restraints (MCL)

Implications: more medial meniscus problems due to lack of mobility

In non-weightbearing: not much difference in mobility (less need for deformity)

In weightbearing: more deformity and sliding

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

How do the menisci move during knee extension?

A

deform and slide anteriorly

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

How do the menisci move during knee flexion?

A

deform and slide posteriorly

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What muscle(s) help the menisci move during knee flexion?

A

medial meniscus by semimembranosis

lateral meniscus by popliteus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What are the most common mechanisms for meniscal tears? Which meniscus is more likely to tear? What causes a springy end-feel/locked knee?

A

twisting/pivoting on loaded limb
medial meniscus
local synovitis (assoc. with inflammation of synovium)
bucket handle tear: meniscus flipped up inside the joint

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What would a yellowish aspiration from menisci mean vs. red aspiration?

A

yellowish fluid: synovitis so not good for surgery b/c cannot heal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Where do the menisci get their nutrition? Where do the different parts receive their nutrients?

A

lateral third gets blood supply up into the pt’s 50s (after fifties only periphery)

peripherally: supplied from capillaries
centrally: relies on diffusion from the synovium (aided by cyclic loading, while immobilization/NWB is problematic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What are the types of articular cartilage injuries?

A

focal lesions (acute): traumatic in origin, focal surface injury, peripheral tissue is normal

degenerative lesions: multiple causes (aging), peripheral tissues affected, OA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What does normal TF alignment consist of?

A

slight genu valgum
170-175 degrees
males > females due to wider pelvis in women (more genu valgum/knock-knee)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What are the two abnormal alignments of TF alignment?

A

genu valgum: knock-knee at <= 165 degrees

genu varum: bow-legged at >= 180 degrees

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

In bilateral stance, what are the mechanical axes?

A

Femur (FM): femoral head to knee center

Tibia (TM): knee center to ankle center

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

How does a varus situation affect the LBA? Implications? Torque?

A

axes are off and LBA comes medial to the knee

compression of medial side can cause wearing of the medial joint compartment

Varus adduction moment

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

How does a valgus situation affect the LBA? Torque?

A

LBA comes outside the knee

causes valgus abduction moment

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

How much does the articular cartilage deform during weight bearing? Single leg stance?

A

deforms by 22-30%

Single leg stance:

Compartment loads: medial bears greatest load at 2.25x BW (lateral: 0.91x BW)

natural varus (adduction) torque due to medial-leaning COM; more pronounced varus torque in bow-legged individuals = medial compression

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

How do we reduce adduction moments?

A

surgically:
osteotomy: surgical wedge to correct alignment (for one with very isolated arthritis); TKA

and conservatively: wedging in someone’s shoe/bracing/gait modification (strengthen quads) to reduce adduction moment

32
Q

What are we referring to with knee osteokinematics? What are the 6 DOF?

A

Flexion/extension
Internal/external rotation
Abduction/adduction (valgus/varus)

tibial and femoral displacement: med/lat, sup/inf, ant/post.

33
Q

How do we measure adduction (varus) and abduction (valgus)?

A

relationship of the distal segment relative to the midline of the proximal segment

34
Q

When the tibia moves medial to the femur’s midline what kind of moment is it?

A

varus (adduction) moment

35
Q

When the tibia moves lateral to the femur’s midline what kind of moment is it?

A

valgus (abduction) moment

36
Q

When the femur moves lateral to the tibia

A

varus (adduction) moment

37
Q

When the femur moves medial to the tibia

A

valgus (adduction) moment

38
Q

If the femur internally rotates, what kind of rotation happens to the tibia?

A

external rotation

39
Q

When femur externally rotates, the tibia moves in what direction relative to the femur?

A

internal rotation

40
Q

How do we describe the relationship of distal and proximal segments in rotation?

A

rel. distal segment relative to midline of the proximal segment

41
Q

During flexion/extension, where is the axis of motion?

What movements occur?

A

horizontal line passing through the femoral epicondyles (axis)

flexion: posterior roll and anterior glide of femur on tibia
extension: anterior roll and posterior glide

42
Q

as we flex and extend does the point of most contact with the tibia and the femur remain or change?

A

changes

43
Q

Where is the point of contact of the TF throughout motion? What is this called?

A

always directly beneath the cruiciate ligaments

four bar linkage system?

44
Q

How do arthrokinematics of the TF work during weight-bearing?

A

weight bearing:

flexion: femoral condyles roll posteriorly and glide anteriorly on the tibial plateaus
extension: femoral condyles roll anteriorly and glide posteriorly on the tibial plateaus

45
Q

How do arthrokinematics of the TF work during non-weight-bearing?

A

non-weight bearing:

flexion: tibial plateaus roll and glide posteriorly on femoral condyles
extension: tibial plateaus roll and glide anteriorly on the femoral condyles

46
Q

What is the ROM for flexion/extension in passive ROM, during gait, and stairs/sitting?

A

Passive: 20-0-160 degrees

Gait: 0-70 degrees

Stairs/sitting: 0-90 degrees

47
Q

How is knee flexion/extension ROM affected by hip position?

A

knee flexion in supine (rectus femoris = quad) is different than prone (hamstrings) b/c they cross both joints

48
Q

Where do most functional activities fall under with Flexion/extension ranges?

A

0-90 degrees

get person 0-90 ASAP after injury

49
Q

What degree of adduction/abduction do you have in full knee extension? in 20 degrees flexion? Why is one more than the other?

A

8 degrees available ROM during extension b/c closed pack position; 13 available during 20 deg. flexion b/c open packed position

50
Q

When sitting at 90 degrees, what is the total amount of internal rotation available? external? Combined?

A

Internal: 0-30 deg.
External: 0-40 deg.
total: 60 to 70 deg.

51
Q

What is the screw home mechanism for the tibia? What kind of chain?

A

External rotation of the tibia on the femur during the last 20° of extension (open chain)

52
Q

What is the screw home mechanism for the femur? What kind of chain?

A

Internal rotation of the femur on the tibia during the last 20° of extension (closed chain)

53
Q

What are the three main reasons for the screw home mechanism?

A

Bony/meniscal structure: (medial femur and tibial condyles are longer AP)

Ligament restrictions: ACL/PCL

slight lateral pull (quads)

54
Q

What is unlocking the knee?

A

internal rotation of the tibia on the femur during early flexion (NWB) via popliteus m.

55
Q

Where is close packed position? What causes it?

A

Full extension creates maximal
bony congruence and
ligamentous tautness

56
Q

Where is loose packed position? What causes it? Relevance to injury?

A

25 degrees of knee flexion

minimal bony congruence

ligaments lax

minimal intra-articular pressure (ex. when landing from jump)

57
Q

What provides TF joint stability?

A

joint capsule goes above the patella
retinacula
synovial lining

58
Q

What are the cruciate ligaments’ location and attachment?

A

intra-articular (inside joint), extra-synovial (synovial lining b/w ligament and synovial fluid; no blood supply)

named according to their tibial attachment

ACL: from anterior aspect of tibia posteriorly and laterally

PCL: from posterior tibia and travels anteriorly and medially

59
Q

ACL has how many bands?

A

two

60
Q

Primary job of ACL?

A

Primary restraint to anterior translation of the tibia on the femur

primary restraint to hyperextension

61
Q

Secondary jobs (2) of ACL?

A

Assists with resistance to internal rotation of the tibia on the femur

Assists with resisting varus and valgus forces

62
Q

What is the maximum excursion at 30 degrees?

A

normal max ant. tibial translation at 5-8 mm

63
Q

What is normal strain on the ACL? Failure?

A

2 to 4 %

6 to 8 % is failure

64
Q

At 90 degrees of knee flexion of isometric contraction of quad as hard as you can, any ACL strain?

A

no

posterior translation of tibia instead

65
Q

At 30 degrees of knee flexion of isometric contraction, any ACL strain? Why is the strain the level it is?

A

yes
anterior translation
activation of quad

less than full extension b/c hamstrings pull posteriorly and protect ACL (no quad pull anteriorly)

66
Q

10 lbs knee extension 0 to 90 strain amt.? Why is the strain the level it is?

A

peak strain farther in extension (10 deg.)
peak is 3.8% strain

tibia is pulled anteriorly by patellar tendon (quads have larger vector and hamstrings have smaller vector)

67
Q

how soon do open change post ACL reconstruction

A

start isolated 90 to 45 bc little strain after 3 to 4 weeks

then full arcs

68
Q

How prevalent are ACL injuries?

A

20% of all knee injuries

70% non-contact

69
Q

Why is the ACL more prone to injury in women?

A

women b/c structural factors: smaller in length, cross-sectional area, and volume

biomechanical factors: Less stiff and fails at lower loads

neuromuscular factors: Area occupied by collagen fiber is lower; peak in quad strength but less hamstring strength after puberty, slower m. activation pattern

70
Q

What biomechanical differences can aid in preventing ACL injuries?

A

Higher knee valgus angles and moments

Decreased Hip flexion angles and knee flexion stiffness during cutting

Greater hip adduction

Trunk adaptations (teach proper trunk position for knee loading)

Hip transverse and frontal plane angles influence knee valgus moments

71
Q

PCL location? Differences from ACL?

A

Runs from superior-anterior-medial (femur) to inferior-posterior-lateral (tibia)

Shorter
Less oblique
Greater CSA (120-150%)
(shorter, broader, less likely to tear than ACL)

72
Q

What is the primary function of the PCL?

A

Restricts posterior translation of the tibia on the femur

tear caused by plantar flexion with fall on tibia, sending it posteriorly

73
Q

most common mechanism for ACL injury?

A

valgus collapse, anterior translation

74
Q

precautions after PCL surgery?

A

limit active hamstring contraction for 3 to 4 mo.

75
Q

What are the secondary functions of the PCL?

A

Assists with resistance to external rotation of the tibia on the femur

Assists with resistance of varus and valgus forces

Unit 2 (29 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions