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Biomechanics > Knee > Flashcards

Knee Flashcards

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1
Q

What does the knee consist of?

A

lateral and medial compartments of tibiofemoral joint and patellofemoral joint

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2
Q

What are the motions of the knee?

A

flexion and extension

internal and external rotation

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3
Q

The shaft of femur angles slightly _____ as it descends toward knee

A

medially

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4
Q

The oblique orientation is a result of natural _____ angle of inclination or proximal femur

A

125 degrees

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5
Q

Why does the knee form an angle in its lateral side of about 170-175 degrees?

A

Because articular surface pf proximal tibia is oriented nearly horizontally

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6
Q

Normal alignment of knee within frontal plane is referred to as:

A

genu valgum

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7
Q

Excessive genu valgum or knock-knee:

A

lateral angle less that 170 degrees

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8
Q

Genu Varum or bow leg:

A

lateral angle greater than 180 degrees

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9
Q

Longitudinal or vertical axis of rotation at hip defined as what:

A

line connecting femoral head with center of knee joint

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10
Q

What does the tibiofemoral joint consist of?

A

articulations between large convex femoral condyles and nearly flat smaller tibial condyles

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11
Q

Large articular surface area of femoral condyles permits:

A

extensive knee motion in sagittal plane for activities such as running, squatting and climbing

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12
Q

What is joint stability provided by?

A

forces and physical containment provided by muscles, ligaments, capsule, menisci and body weight

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13
Q

The transformation of the lateral mensici into shallow seat for femoral condyle is most important because:

A

flat to slightly convex shape of tibia’s lateral articular surface

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14
Q

What anchors menisci to intercondylar region of tibia?

A

free ends, known as anterior and posterior horns

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15
Q

External edge of each meniscuc attached to tibia and adjacent capsule by what?

A

coronary (or meniscotibial) ligaments

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16
Q

What do the coronary ligaments allow menisci to pivot freely during movement?

A

because the coronary ligaments are relatively loose

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17
Q

What connects both menisci anteriorly?

A

transverse ligament

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18
Q

What muscles attach to both menisci?

A

quads and semimembranosus

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19
Q

What muscle attaches to lateral meniscus?

A

popliteus

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20
Q

What helps to stabilize the position of menisci?

A

muscle attachments

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21
Q

Where is blood supply of the menisci greatest?

A

near peripheral (external) border

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22
Q

Internal border of menisci is essentially:

A

avascular

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23
Q

Where is blood from capillaries located within:

A

adjacent synovial membrane and capsule

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24
Q

The shape of the medial meniscus is:

A

oval shape

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25
The shape of the lateral meniscus is:
circular shape
26
External border of the medial meniscus attaches to:
to deep surface of MCL and adjacent capsule
27
External border of the lateral meniscus attaches:
only to lateral capsule
28
What passes between LCL and external border of lateral meniscus?
tendon of popliteus
29
What is the primary function of menisci?
reduce compressive stress across tibiofemoral joint
30
What are other functions of menisci?
Stabilizing joint during motion Lubricating articular cartilage Providing proprioception Helping to guide knee's arthrokinematics
31
Br tripling area of joint contact, menisci significantly ______ pressure on articular cartilage
decrease
32
Complete lateral meniscecetomy increases:
contact pressure at knee by 230% | increases risk of developing stress related OA
33
What is the most common injury of the knee?
tears of meniscus
34
What are meniscal tears associated with?
forceful axial rotation of femoral condyles over partially flexed and weight-bearing knee
35
What can pinch and dislodge meniscus?
Axial torsion within compressed knee
36
What is a bucket-handle tear?
Dislodged or folded flap of meniscus that can mechanically block knee movement
37
What is the MOI for medial meniscus?
axial rotation and external valgus force applied to lateral aspect of knee
38
What can valgus force cause?
subsequent large stress on MCL and posterior-medial capsule
39
How many degrees of freedom does the tibifemoral joint posses?
two degrees of freedom: flexion and extension (sagittal plane) internal and external rotation (provided knee slightly flexed)
40
When does frontal plane motion at the knee occur?
passively only limited to 6-7 degrees
41
The ML axis or rotation for flexion and extension is not fixed but migrates with:
femoral condyles
42
The curved path of axis is known as:
evolute
43
The Path of axis influenced by:
eccentric curvature of femoral condyles
44
The migrating AOR does what two things:
- alters length of internal moment arm of flexor and extensor muscles of knee - external devices that attach to the knee rotate about fixed axis of rotation
45
Internal and external rotation occurs about a:
vertical or longitudinal axis of rotation | also called axial rotation
46
Freedom of axial rotation increases with:
greater knee flexion
47
When the knee is flexed to 90 degrees:
about 40-45 degrees of total axial rotation
48
External rotation range of motion generally exceeds internal rotation by ratio of about:
2:1
49
When is axial rotation maximally restricted:
once knee is in full extension
50
What is rotation blocked by:
passive tension in stretched ligaments, capsule, and increased bony congruity within joint
51
During tibial-on-femoral extension, articular surface of tibia:
rolls and slides anteriorly on femoral condyles
52
During femoral-on-tibial extension (standing up from deep squat)
femoral condyles simultaneously roll anteriorly and slide posteriorly on articular surface of tibia
53
What directs roll of femoral condyles and stabilizes menisci against horizontal shear caused by sliding femur?
quads
54
What does the locking of knee in full extension require?
10 degrees of external rotation
55
What is the screw home mechanism?
Rotary locking action | rotation observable during 30 degrees of extension
56
For knee that is fully extended to be unlocked the joint must first:
internally rotate
57
What muscle drives the internal rotation of the knee?
popliteus
58
What can the popliteus muscle do?
rotate femur externally to initiate femoral-on-tibial flexion or can rotate tibia internally to initiate tibial-on-femoral flexion
59
What position must the knee be in to maximize independent axial rotation b/w tibia and femur?
flexed
60
What is the function of the MCL (and posterior-medial capsule):
1. Resists valgus (abduction) 2. Resists knee extension 3. Resists extremes of axial rotation (especially knee external rotation)
61
What is the common MOI of MCL (and posterior-medial capsule):
1. Valgus-producing force with foot planted (e.g., “clip” in football) 2. Severe hyperextension of knee
62
What is the function of the LCL?
1. Resists varus (adduction) 2. Resists knee extension 3. Resists extremes of axial rotation
63
What is the common MOI of the LCL?
1. Varus-producing force with foot planted | 2. Severe hyperextension of knee
64
What is the function of the ACL?
1. Most fibers resist extension (either excessive anterior translation of tibia, posterior translation of femur, or a combination thereof) 2. Resists extremes of varus, valgus, and axial rotation
65
What is the common MOI of the ACL?
1. Large valgus-producing force with foot firmly planted 2. Large axial rotation torque applied to knee (in either rotation direction), with foot firmly planted 3. Any combination of above, especially involving strong quadriceps contraction with knee in full or near-full extension 4. Severe hyperextension of knee
66
What is the function of the PCL?
1. Most fibers resist knee flexion (either excessive posterior translation of tibia or anterior translation of femur, or a combination thereof) 2. Resists extremes of varus, valgus, and axial rotation
67
What is the common MOI of the PCL?
1. Falling on fully flexed knee (with ankle fully plantar flexed) such that proximal tibia first strikes ground 2. Any event that causes forceful posterior translation of tibia (i.e., “dashboard” injury) or anterior translation of femur, especially while knee is flexed 3. Large axial rotation or valgus-varus applied torque to knee with foot firmly planted, especially while knee is flexed 4. Severe hyperextension of knee causing a large gapping of posterior side of joint
68
Approximately 70% of ACL sporting-related injuries occur through what?
non-contact or minimal contact
69
Muscles of the knee describes asL
- knee extensors | - knee flexor-rotators
70
Sartorius action:
Hip flexion, external rotation, and abduction | Knee flexion and internal rotation
71
Gracilis action:
Hip flexion and adduction | Knee flexion and internal rotation
72
Quads action: | rectus femoris and vastus group
Knee extension and hip flexion | Knee extension
73
Popliteus action:
Knee flexion and internal rotation
74
Semimembranosus action:
Hip extension | Knee flexion and internal rotation
75
Semitendinosus action:
Hip extension | Knee flexion and internal rotation
76
Biceps femoris (short head) action:
Knee flexion and external rotation
77
Biceps femoris (long head) action:
Hip extension | Knee flexion and external rotation
78
Gastrconemius action:
Knee flexion | Ankle plantar flexion
79
Plantaris action:
Knee flexion | Ankle plantar flexion
80
What is external torque of the knee equal to:
external load being moved or supported, multiplied by its external moment arm
81
When is the internal moment arm used by the quads the greatest?
between 60 and 20 degrees of knee flexion
82
When is the internal moment arm used by the hamstrings (knee flexors) the greatest?
between 50-90 degrees of knee flexion
83
What are the two inter-related factors associated with joint compression force on the patellofemoral joint:
Force within quadriceps muscle | Knee flexion angle
84
The larger the Q angle, the greater:
lateral muscle pull on patella
85
Opposing forces do what so that the patella tracks optimally during flexion and extension?
counteract
86
What can increase the Q angle?
excessive knee valgus and knee external rotation
87
Increased external rotation of the knee can occur as a combination of what?
excessive internal rotation of femur and external rotation of tibia

Biomechanics (13 decks)

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