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Biomechanics > Knee > Flashcards

Knee Flashcards

0
Q

What bones are involved in the knee joint?

A

Femur, tibia, patella

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1
Q

What type of joint is the knee joint?

A

Modified ginglymus joint (hinge joint)

Provides flexion and extension

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2
Q

Joints of the knee

A

Tibiofemoral joint

Patellofemoral joint

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3
Q

Tibiofemoral joint

A

Proximal concave tibia articulated with the convex distal femur

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4
Q

What makes the tibia concave for the tibiofemoral joint?

A

Meniscus

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5
Q

Patellofemoral joint

A

articulation of posterior surface of the surface of the patella and the trochlear surface of the anterior femur

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6
Q

What is the Q Angle?

A

Alignment at patellofemoral joint formed between a line connecting the ASIS to the midpoint of the patella and a line to the tibial tuberosity

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7
Q

What is a normal Q-angle?

A

185-190 degrees

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8
Q

What can a smaller than normal Q-angle cause?

A

increased medial knee pressure

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9
Q

What can a larger Q-angle cause?

A

Increase lateral knee pressure

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10
Q

Genu Valgum

A

(knock kneed) q-angle greater than 190….5-10 is normal and normally higher on females
increase compression in lateral compartment of the knee

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11
Q

Genu Varum

A

(bow legged) knee angle less than 170…less common.
Can be predisposed by: coxa vara-angle less than 125/weak hip abductors
increase compression in medial compartment of knee

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12
Q

Genu Recurvum

A

(hyperextension) extension beyond +10 of neutral
area of condyles in contact during end range extension is decreased resulting in increased compressive forces secondary to smaller area

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13
Q

Proximal Tibioiblar

A

Articulation of the proximal tibial and fibula

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14
Q

What are some functions of the proximal tibiofibular joint?

A

Dissipation of torsional stresses applied at ankle
Dissipation of lateral tibial bending movements
Tensile weight bearing (most joints have compressive forces)
movement occurs with movement of ankle

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15
Q

Does proximal tibiofibular joint move the same or opposite direction of the distal tibiofibular joint?

A

Opposite

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16
Q

What type of joint is the tibiofemoral joint?

A

Double condyloid synovial joint

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17
Q

Tibiofemoral Joint

A 
3 degrees of freedom
convex femur articulates with concave tibia
2 perspectives (tibia on femur-open/femur on tibia-closed)
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18
Q

Arthrokinematics of Tibiofmoral Joint

A

Open Chain-Roll and Glide occur together

Closed Chain-Roll and Glide opposite

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19
Q

Tibia on Femur Arthrokinematics

A

(concave on convex)
Extension: Anterior Roll and Glide
Flexion: Posterior Roll and Glide
IR/ER=spin?

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20
Q

Femur on Tibia Arthrokinematics

A

(convex on concave)
Extension: Anterior Roll and Posterior Glide
Flexion: Posterior Roll and Anterior Glide
IR/ER: Spin?

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21
Q

Tibiofemoral Closed

A

Full Extension w/ ER

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22
Q

Tibiofemoral Open

A

25-30 Knee Flexion

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23
Q

Tibiofemoral Capsular Patter

A

Flexion > Extension

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24
Q

Screw Home Mechanism

A

Occurs in the final 20-30 degrees of knee extension
If the foot is planted on the floor with knee flexed, extension of the knee causes:
-ACL to become tight which restrits movement of lateral femoral condyle
-Medial condyle isnt so keeps moving
-causes tibial ER (Femoral IR)
-This “locks” the knee at full extension

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25
Q

what happens if this lock knee does not occur?

A

Other joints compensate, shortened flexors and lengthened extensors

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26
Q

What muscle unlocks the knee?

A

Popliteus - causes the tibia to medially rotate during flexion of the knee

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27
Q

Patellofemoral Joint

A

Patella slides along fixed intercondylar groove in open chain
Intercondylar groove slides along fixed patella in closed chain
most commonly referred at open chain

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28
Q

What is a function of the patellofemoral joint?

A

increases the angle of insertion for quads and increases the torque producing capacity for quads

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29
Q

Gliding motions of patellofemoral joint

A 
flexion and extension (superior and inferior glides)
medial and lateral glides
medial and lateral tilts
medial and lateral rotation
anterior and posterior tilts
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30
Q

Patella Alta

A

High Riding Patella

Increased length of patella tendon and higher chance of subluxation

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31
Q

Patella Baja

A

Low riding patella

shortened patella tendon…increases compression can lead to arthritis

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32
Q

Contraction of quads causes a ______ compressive force on the patella.

A

increased

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33
Q

What type of joint is the proximal tibiofibular joint?

A

Plane synovial joint

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34
Q

Proximal Tibiofibular Joint

A 
Proximal fibular slightly convex articulating with the slightly concave proximal tibia
3 degrees of freedom
-anterior/posterior
-superior/inferior
-rotation
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35
Q

Tibiofibular joints open positions

A

0 degrees plantar flexion

36
Q

Tibiofibular joints closed position

A

full ankle dorsiflxion

37
Q

Tibiofibular joints capsular pattern

A

pain with biceps femoris muscle contraction

38
Q

Lateral Patellar Tracking

A

*Tight lateral bands
ITB
Bowstringing (more common in runners)
Lateral patellar retinacular fibers

39
Q

Medial Patellar Tracking

A

*tight medial fibers/muscle activity
VMO
Raised lateral facet
Medial Patellar retinacular fibers

40
Q

External Force Patellar Tracking

A

Valgus force (increased genu valgum-to compensate)
ER of femur
IR of Tibia

41
Q

What are the effects of patellar tracking?

A

increased tension at Quadricep Tendon and Patellar Tendon

increases bowstringing force

42
Q

Where is the Anterior Cruciate Ligament (ACL) located?

A

Attaches to the anterior tibia and runs in a posterior, lateral, and proximal direction attaching to lateral femoral condyle.

43
Q

What are the bands of the ACL?

A

Anteromedial
Intermedial
Posterolateral

44
Q

What are the functions of the ACL?

A
  1. most effective in extension
  2. resist excessive tibial anterior slide/translation
  3. resist excessive femoral posterior slide/translation
  4. Resist excessive axial rotation, varus and valgus
  5. resists knee extension (prevent hyperextension)
45
Q

Which bands of the ACL are tight/slack in knee extension?

A

posterolateral band tight (control rotation at tibia) and anteromedial band is slack

46
Q

Which bands of the ACL are tight/slack in knee flexion?

A

Posterolateral band is slack

Anteromedial band is tight

47
Q

How is the ACL injured?

A

Large valgus force with foot planted
Large axial rotation force applied with foot planed
Combination of the previous two
Severe hyperextension

48
Q

What is the Terrible Triad

A

ACL, MCL, Medial Meniscus

49
Q

Can cruciate ligaments repair on their own?

A

No

50
Q

Where is the Posterior Cruciate Ligament (PCL) located?

A

Attaches to the posterior tibia and runs in a proximal, medial and anterior direction attaching to the medial femoral condyle

51
Q

What is the function of the PCL?

A

Most effective in flexion
Resist excessive tibial posterior slide/translation
Resist excessive femoral anterior slide/translation
Resist excessive axial rotation, varus, and valgus forces

52
Q

How is the PCL injured?

A

Falling on fully flexed knee with proximal tibia striking 1st
Force posterior translation of tibia
Worse with increasing flexion
Rotation, varus, and/or valgus force applied w/ foot planted
Severe hyperextension w/ gapping to posterior side

53
Q

Where is the Medial Collateral Ligament (MCL) located?

A

Superficial Portion - Attaches proximally to the medial femoral epicondyle and distally and shaft of the tibia and tibia condyle
Deep portion- attaches to medial meniscus and blends with joint capsule

54
Q

What is the function of the MCL?

A

Resists valgus force, knee extension, reinforce medial capsule and prevent ER of leg with knee extended

55
Q

How is the MCL injured?

A

Valgus force with foot planted or severe hyperextension

- most commonly torn with ACL

56
Q

Where is the Lateral Collateral Ligament (LCL) located?

A

Runs from the lateral epicondyle of the femur to the head of the fibula

57
Q

Does the MCL or LCL attach to adjacent meniscus?

A

Only the MCl

58
Q

What is the function of the LCL?

A 
Resist varus force
Resist knee extension
Prevent ER of the leg (with knee extension)
Reinforce lateral capsule
Reinforce posterior-lateral capsule
59
Q

How is the LCL injured?

A

Varus force with foot planted

Severe hyperextension

60
Q

What structures reinforce the capsule of the knee anteriorly?

A 
Connective tissue (patellar tendon and retinacular fibers)
Muscular - tendinous (quads)
61
Q

What structures reinforce the capsule of the knee laterally?

A 
Connective tissue (LCL, lateral retinaculum, ITB)
Muscular-tendinous (biceps femoris, popliteus, gastroc)
62
Q

What structures reinforce the capsule of the knee posteriorly?

A 
Connective tissue (oblique popliteal ligament, arcuate ligament)
Muscular-tendinous (gastrocs, hamstrings)
63
Q

What structures reinforce the capsule of the knee posterior-lateral?

A

Arcuate complex, LCL

Popliteus

64
Q

What structures reinforce the capsule of the knee medially?

A

Retinaculum, MCL, posterior-medial capsular, posterior oblique ligament
Pes anserine

65
Q

What muscles have an insertion point that make the pes anserine?

A

Semitendinosus, gracilis, sartorius

66
Q

What is the most common orthopedic repair?

A

Meniscus

67
Q

What are the meniscus?

A

Fibrocartilaginous discs

Located directly between the femoral condyles and the tibial plateau

68
Q

Why does the meniscus have limited healing potential?

A

the meniscus only has a peripheral blood supply so it cannot heal on its own

69
Q

What is the function of the meniscus?

A

Deepen surface of the tibia
makes a concavity atop the tibial plateauj
Shock absorbers (compression provides nutrients?)

70
Q

Which meniscus is more likely to be injured?

A

Medial by 2X

71
Q

What are characteristics of the medial meniscus?

A

larger and more C-shaped
anterior and posterior horns
Firms attachment to the MCL and medial capsule

72
Q

Why is the medial meniscus more frequently injured?

A

Due to firm attachment to the tibia and decreased mobility makes it more prone to injury

73
Q

What are characteristics of the lateral meniscus?

A

More circular shape, loosely attached to tibia and absorbs more of the stress for less inury

74
Q

What soft tissues attach to the meniscus?

A

MCL and semimembranosus to Medial

Poplieus to Lateral

75
Q

How does the menisci move during knee extension?

A

menisci move anteriorly with tibia

76
Q

How does the menisci move during knee flexion?

A

menisci move posterior with tibia

77
Q

How are the menisci injured?

A

axial rotation and valgus force most common

78
Q

50 percent of all ______ tears associates with meniscal injury.

A

ACL

79
Q

Injury can be associated with early onset ________

A

Osteoarthritis……less cartilage = less shock absorption

80
Q

What is the function of bursae in the knee?

A

Reduces friction between the moving structures

81
Q

Infrapatellar Fat Pad

A

Between the patellar tendon and tibia
Very sensitive
Helps reduce friction in the knee

82
Q

What muscles extend the knee?

A 
Quads 
 -rectus femoris
 -vastus medialis
 -vastus lateralis
 -vastus imtermedius
Articularis genu
83
Q

What muscles flex the knee?

A 
Hamstrings
 -semitendinosus
 -semimembranosus
 -bieps femoris (long and short head)
Sartorius
Gracilis
Popliteus
Gastrocnemius
Plantaris
84
Q

What knee flexor is not biarticular?

A

Popliteus

85
Q

What is the length tension relationship?

A

Muscles at full contraction or extension lose contractile capabilities

86
Q

Active insufficieny

A

Extreme shortened muscle results in decreased motor recruitment (must shorten over both joints)

87
Q

Passive insufficiency

A

Tightened/lengthened muscles causes decreased muscle contraction

Biomechanics (4 decks)

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