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Movement Science > Knee > Flashcards

Knee Flashcards

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1
Q

What is the purpose of the patella at the knee joint

A

increases mechanical advantages of patellar tendon

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2
Q

What are the articulation s at the knee joint

A

-tibiofemoral (medial and lateral): they have mensci
-patellofemoral: patella sits in a groove
-tibiofibular joint proximal: below the femur and therefore is somewhat separate

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3
Q

How does the knee function in limb length

A

has a lot to do with how long the limb is
-elongate the limb= extend it
-shorten the limb = flex it

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4
Q

How does the knee function in mobility of the foot

A

-by changing the knee, the foot will change trajectory
-some rotation at both the knee and the foot

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5
Q

how does the knee function in stability:

A

can lock in the closed pack position (extension)

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6
Q

Conversation of momentum

A

-as we step and the foot leaves the ground the whole limb comes with it
-swing the femur forward and the tibia and fibula will come with

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7
Q

how does the knee function in Transmitting loads

A

-weight shifts, and ground reaction forces

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8
Q

what are force couples at the knee

A

-through the thigh muscles and calf muscles that work like a force couple

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9
Q

how does the knee sustain high foces

A

-two long sticks with a joint in the middle allow it to sustain forces

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10
Q

Tibiofemoral joint (femoral surface)

A

-two condyles on the femur
-medial side is longer anterior to posterior therefore causing some rotation
-between the condyles is an intecondylar notch that contains the ACL and the PCL
-epicondyles: muscle attachments

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11
Q

Tibiofemoral joint (tibial suface)

A

concave
-fits with femur and has an intercondylar eminence where the ACL/PCL attach

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12
Q

Patella articular surfaces

A

medial facet:
- odd facet: comes into play with more flexion
lateral facet:
vertical ridge is in the intercondylar groove

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13
Q

Alignment and weight-bearing: anatomical axis

A

directed inferiorly and medially
-not a straight line = have a little bit go valgus (gene valgum)

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14
Q

Alignment and weight-bearing: angle between tibia and femur

A

170-175
-genu valgum
-BOS is closer together it gives more stability when switching weight

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15
Q

Alignment and weight-bearing: mechanical axis

A

from head of femur to talus
-3º from vertical axis

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16
Q

Abnormal genu valgum

A

“knock knees”
-has coxa varum
-excessive pronation at the feet
-angle is <165º

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16
Q

Abnormal genu valgum

A

“knock knees”
-has coxa varum
-excessive pronation at the feet
-angle is <165º

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17
Q

Abnormal genu varum

A

“bow legged”
-has coxa valgum
-angle is> 180º

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18
Q

What is the normal Q angle for males versus females

A

Males: 13-15º
Females: 15-18º
-females have more flare, and a higher angle that causes more instability at the knee
-affects the line of pull by the quads

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19
Q

What is the Q angle

A

the angle between the lines
1. mid patella to tibial tuberosity
2. mid patella to ASIS

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20
Q

What is the extensor retinaculum at the knee and what does it do?

A

it is a fibrous sheath that provides stability

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21
Q

what is dynamic verse static support

A

dynamic: muscular
static: bones and ligaments and tendons

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22
Q

What is the role of the menisci

A

dissipate force from Body weight and ground reaction force

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23
Q

What is the blood supply like for the menisci

A

the blood supply is on the outside and therefore central tears do not heal well

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24
Q

Describe the medial menisci shape and attachments

A

~ C- shaped
~ thicker
~ attached to MCL, semimembranousus and tibia

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25
Q

Describe the lateral menisci shape and attachments

A

~ O shaped due to the rotation of the femur on the tibia
~ more mobile
~ attached to PCL, popliteus, Joint capsule, and coronary ligament, sometimes ACL

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26
Q

Describe the normal forces that the menisci receive in weight bearing
-walking
-ascending stairs
-running
-max isokinetic knee extension

A

-walking: 2.5-3 x body weight
-ascending stairs: 4 times BW
-running: 5-6 body weight
-max isokinetic knee extension: 9x body weight
- 40%-60% of the force is absorbed by the menisci and ligaments and muscles absorb the rest of the force

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27
Q

Clinical considerations when removing the meniscus versus a meniscus repair

A

Remove the meniscus:
- changes in Weight bearing
- increase contact pressures by 230%

Repair:
- considerations for healing

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28
Q

What are the osteokinematics of the knee

A

flexion: 0-140
extension: 0-5-10

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29
Q

what happens with knee movement such as ER/IR in a flexed versus extended position

A
  • in a flexed position you can get one medial and lateral rotation where as in extension you cannot because this is closed pack position
    -this rotation occurs as well during movement due to th medial condyle being longer anterior to posterior
30
Q

ROM for knee
-sitting
-walking
-other activities like squatting, sitting cross legged on the floor ETC

A
  • sitting: 90º of flexion
    -Walking:
    • level surface: 0-70º
    • up and down the stairs 0-80º
      -other: 115º
31
Q

Describe the screw home mechanism

A

-medial is longer anterior to posterior and therefore causes a rotation around the lateral side
-ER of tibia on femur as you come into terminal extension in last 35º
-IR of the femur on the tibia as you come into terminal extension in closed chain

32
Q

Contributions to screw home mechanism

A
  1. shape of medial condyle
  2. tension in ACL
  3. Lateral pull of quads
33
Q

What adds to tibiofemoral joint stability

A
  1. capsule
  2. extension retinaculum
  3. synovial lining
  4. ligaments:
  5. muscles
34
Q

What does the ACL resist

A

anterior translation of tibia on femur and controls rotation (always under tension)

35
Q

What does PCL resist

A

posterior translation of tibia on femur and controls rotation
(always under tension)

36
Q

Arthrokinematics of flexion and extension in open chain

A

flexion: posterior roll and glide and a medial pivot to unlock the knee

Extension: anterior roll and glide

37
Q

Arthrokinematics of flexion and extension in closed

A

flexion: posterior roll and anterior glide/lateral rotation

extension: anterior roll and posterior glide/medial rotation

38
Q

Describe the pressure points on the patella during flexion

A

20º flexion: towards apex
60º flexion: superior to 20º
90º flexion: towards the base of the patella
135º flexion: towards the odd facets (get tilted due to rotation)

39
Q

Anterior/posterior stability

A

ACL/PCL
-synovial membrane wraps around them
-more elastin in ligaments
-interwoven to increase strength against tensile forces
-good vascular supply

40
Q

Medial/lateral stability

A

MCL/LCL

41
Q

rotational stability

A

Medial: MCL is twisted
Lateral: LCL is twisted

42
Q

ACL
-resists
-mechanism of injury

A

Resists:
1. anterior shear/translation
2. extension
3. varus/valgus/axial rotation

Mechanism of injury:
1. hyperextension
2. large valgus force
3. axial rotation with valgus or extension

43
Q

PCL
-resists
-mechanism of injury

A

-resists
1. posterior shear/translation
2. flexion
3. hyperextension
4. varus/valgus/axial rotation

-mechanism of injury
1. hyper flexion
2 posterior translation of tibia on fetus
3. hyperextension
4. valgus or varus

44
Q

MCL
-resists
-mechanism of injury

A

-resists
1. valgus
2. extension
3. axial rotation

-mechanism of injury
1. valgus force
2. hyperextension

45
Q

LCL
-resists
-mechanism of injury

A

-resists
1. varus
2. extension
3. axial rotation

-mechanism of injury
1. varus force
2. hyperextension

46
Q

Anterior drawer test

A

pulling the tibia out to see if it is restricted
-anterior shear created by the quads

47
Q

Posterior drawer test

A

pushing the tibia to see if it is restricted
-tibia gets posterior shear from the hamstrings

48
Q

Ratio of length of patellar tendon to patella

A

1:1

49
Q

Patella baja

A

when the tendon is shorter than patella and therefore the patella sits more distal in the leg

50
Q

Patella alta

A

the tendon is longer and the knee is more likely to dislocate or sublux
-the patella sits more proximal

51
Q

Patella tracking patterns (how can it move)

A

-the patella can tilt, rotate and more side to side

52
Q

Patella stability in flexion and extension

A

Full extension: passive and active tension
- muscles, tendons and retinaculum

as flexion increases more stability from boney contact

53
Q

Patellectomy

A

the patella increases the moment arm of the quads, need this for terminal extension
-extensor lag can occur without the patella and therefore they will not get into terminal extension (an active lag with full PROM)
- a lot of swelling can also call extensor lag

54
Q

Where is the resultant force vector for the quads pointed

A

up and laterally in the same direction the patella moves

55
Q

Where is the major force on the patella from the quads?

A

Superior and laterally

56
Q

Where is the more torque generated during knee extension by the quads?

A

about 45 degrees of flexion
(due to the two joint muscles if causes the force to shift away from mid range)

57
Q

Where is the most torque generated during knee flexion by the hamstrings

A

Maximum torque is generate at 5 degrees of knee flexion

58
Q

Which muscles produces the most torque at the knee

A

-the vastus
-hamstrings
-rectus femoris (designs motion not torque production)
-gastrocnemius
-other (popliteus and planteris)

59
Q

Shearing in the tibiofemoral joint

A

also increases when the quads are working

60
Q

Shear/compressive forces as you go into extension during Open chain

A
  • as you go into extension compressive forces decrease
    -shearing forces increase as you go into OC terminal extension due to patella pulling anteriorly
61
Q

Shearing and compressive forces as you go into extension in Closed chain
-flexion closed chain

A

-as you go into extension there is higher compressive forces and decreased shearing by activating hamstrings - as you go into flexion: patella compressive forces increases and the shear forces increase

62
Q

How can you reduce shearing and compression to protect the ACL

A

-OC: in more flexion; Go from 90-30 to reduce the rotation that occurs in terminal rotation
-CC: in more terminal extension; control the tibia by cocontracting with the hamstrings

63
Q

How can you reduce shearing and compression to protect the Patella

A

OC/CO: outside of the painful arc (above and below)

64
Q

How can you reduce shearing and compression to protect the meniscus

A

OC in mid range limit WB/terminal extension to limit the rotation and watch the activation of the hamstings

65
Q

Where in the gait cycle are you closetes to full extension and then closest to most flexion?

A

-extension: mid stance
-flexion: from toe off to mid swing due to bringing it closest to the axis of rotation and use less energy

66
Q

What are the knee kinematics in the front plane during gait?

A

-condyles can rock a little bit
-switching sides are the peaks of of the rocking
-motion is minimal
-abduction and adduction

67
Q

Internal and external rotation of the knee during gait

A

-internal rotation is associated with the knee flexion
-external rotation is associated with knee extension

68
Q

What is the unhappy triad?

A

-mutlidirection instability of rotation instability (ligament injuries)
-usually ACL, MCL, and medial or lateral meniscus
-medial = valgus force and more anterior; tears are normally in the perpherial
-lateral = varus, posterior, compressive or central tears

69
Q

Osteochondritis Dissecans

A

-Stage 1 a bulge on medial femoral condyle
-stage 2: separation of the medial condyle
-stage 3: fragment of cartilage and bone separates
(loose body)
-ROM is sometimes limited when it is stuck

70
Q

Osteoarthritis cause

A

-reduces hip abductor torque potential
-abnormal forces due to weak hip ER and ABD

71
Q

Genu valgum vs varus

A

-genu valgum corresponds to coxa vara, and excessive pronation
- genu varum corresponds to coxa valgum and excessive supination

72
Q

Genu Recurvatum

A

-young females are more prone to this
-hyper extended knees cause stretch in the posterior structures
-change in compressive foreces in the anterior
-quads are weak and therefore the screwhome mechanism makes it more stable

Movement Science (17 decks)

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