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ORTHO 560 > knee anatomy and biomechanics > Flashcards

knee anatomy and biomechanics Flashcards

1
Q

what joints make up the knee joint?

A

Patella-femoral joint
Tibiofemoral joint
Superior tibio-fibular joint

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2
Q

why is the knee joint susceptible to trauma

A

stuck in the center of two lever arms

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3
Q

what provides inert stability to the knee?

A

ligament
meniscuc
articular surfaces

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4
Q

what provides dynamic stability to the knee joint?

A

muscles

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5
Q

what forms the normal Q angle of the knee

A

line from asis to center of the patella and from center of patella to tibial tibercle

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6
Q

what is associated w/ an increase in Q angle of the knee

A

increased lateral translation and thus increase stress on the side of PF joint

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7
Q

what attaches the patella to tibial tuberosity

A

patellar tendon

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8
Q

what is the function of the PF joint

A

pulley for the quad muscles and allows to decrease the friction b/w the quad tendon and the femoral condyles

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9
Q

what happens at the PF joint as the knee begins to flex

A

patella moves inferiorly and engage in the intercondylar groove
shifts medially by being pushed by the large lat femoral condule and tibial MR

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10
Q

what happens at the PF joint as the knee past 30 degree flexion

A

patella will either remain stable or shift laterally

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11
Q

at 0 degree of knee flexion (knee extension) where does contact of the patella occur?

A

no contract b/w patella and torchlear groove

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12
Q

at 10-30 degrees of knee flexion where does contact of the patella occur?

A

inferior pole of patella and trochlear groove

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13
Q

45-60 degrees of knee flexion where does contact of the patella occur?

A

contact area moves towards the central pole of the patella

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14
Q

at 90 degrees of knee flexion where does contact of the patella occur?

A

the top of the patella is in contact w/ the patellar groove

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15
Q

at 135 degrees of knee flexion where does contact of the patella occur?

A

medial and lateral sides of the trochlea now serve as contact points

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16
Q

how is the congruency of the knee joint?

A

incongruent due to the different shape of the articulating surfaces; patellar surface is smaller than femoral articulating surface

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17
Q

what act as dynamic stabilizers for the patella

A

quad tendon
patellar tendon
ITB
rectus femoris muscle

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18
Q

what acts as static stabilizers of the patella

A

medial and lateral patellar retinaculum

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19
Q

what may influence the position of the patella

A

imbalances in passive tension or change ion the line of pull of the dynamic stabilizers

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20
Q

what determines the vertical position of the patella in the femoral sulcus?

A

lenght of the patellar tendon

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21
Q

what is patella alta

A

condition that arises when the patellar tendon is abnormally long; leading for a higher raised patella on the femoral sulcus

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22
Q

what are consequences associated to patella alta?

A

subluxation and PFPS

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23
Q

what is the normal and abnormal raio for modified insall-salvatti ratio and what does it measure?

A

Ratio patella tendon length: patella length
Normal ratio = 1.25 : 1
Abnormal ratio = >2: 1

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24
Q

what does the joint reaction force on the knee depend on?

A

quad force and knee angle

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25
Q

what happens to the patella and joint rxn force when the knee is in increased flexion?

A

patella gets pulled up by the quad tendon and inferiorly by the patellar tendon leading to posterior compression

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26
Q

when is the compression force on the patella minimal?

A

w/ knee extension

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27
Q

when is compression force on the patella worse?

A

in 90 degree flexion and w/ quad contractions

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28
Q

what is the approximate compression force on the patella w/walking?

A

~25-50% BW

29
Q

what is the approximate compression force on the patella w/ running

A

5-6x BW

30
Q

when does the knee joint reaction force increase w/ CKC

A

w/ knee flexion

31
Q

when does the knee joint reaction force increase w/ OKC

A

w/ knee extension

32
Q

describe the osteokinematics of the TF joint?

A

Flexion= caudal glide
Extension: cranial glide
Tibia IR: lateral glide
Tibial ER: medial glide

33
Q

what type of joint is the PF joint?

A

modified ovoid joint

34
Q

what are the articulating surfaces of the TF joint

A

Femoral condyles: convex

Tibial plateau: concave

35
Q

what are the abd and add mvmts of the knee considered as?

A

not physiological mvmt but can be assessed w/ glides

36
Q

expain the arthrokinematics of the TF joint

A

flexion: posterior glide
extension: anterior glide
abd: lateral glide
add: medial glide

37
Q

what is the resting position of the knee

A

30 degree flexion

38
Q

what is the CPP of the knee

A

full extension and ER

39
Q

what is the capsular pattern of the knee

A

greater limitation of flexion > extension

40
Q

where is the prepatellar bursae of the knee?

A

b/w skin and anterior patella

41
Q

what is the most commonly affected bursae of the knee?

A

prepatellar bursae

42
Q

what is the suprapatellar bursae?

A

located b/w rectus femoris ms and femur

43
Q

where is the deep infrapatellar bursae

A

b/w patellar tendon and tibia

44
Q

where is the superficial/subcutaneous infrapatella bursa?

A

b/w skin and tibial tuberosity

45
Q

where is the semimembranosis bursae located?

A

located b/w medial head of gastroc and capsule of the knee

46
Q

where is the semitendinosis bursa

A

between tibia and pes anserine

47
Q

when is the ST bursae generally an issue?

A

w/ knee over use injuries

48
Q

how is the MCL of the knee

A

broad and flat shapes

ranges from medial femoral epicondyle to medial proximal shaft of the tibia and attachments to medial menisus

49
Q

what happens on brush test w/ MCL tear of the knee

A

negative brush test (no effusion) since its a extra articular ligament

50
Q

what is the function of MCL of the knee

A

prevents valgus stress and tibia IR

51
Q

how is the LCL of the knee

A

round in shape

extends from lateral epicondyle of the femur to the upper end of the lateral fibula

52
Q

does the LCL of the knee attach to meniscus

A

no

53
Q

what happens on brush test w/ LCL of knee rupture?

A
  • brush test since extraarticular
54
Q

what is the function of LCL of the knee

A

prevents varus stress

55
Q

where does the ACL of knee extend from?

A

From anterior medial aspect of the tibia and extends superiorly/ posteriorly to femoral condyle

56
Q

what type of ligament is the ACL of the knee?

A

intra articular thus lot of swelling when injured

57
Q

what is the fct of ACL of the knee?

A

Restrains anterior translation of tibia on femur
Backwards sliding of the femur and hyperextension of the knee
Controls tibia IR on the femur in femoral extension of 0-30 degrees

58
Q

is there a difference b/w strain on ACL in CKC or OKC?

A

no difference

59
Q

what can help control force on ACL in CKC

A

the hamstrings co-contraction

60
Q

where does the PCL of the knee extend from

A

From posterior tibia and extends superiorly and anteriorly to medial femoral condyle

61
Q

what type of ligament is the PCL?

A

Intra-articular and extra synovial ligament: issue will lead to knee effusion

62
Q

what is the function of the PCL?

A

restrains posterior translation of the tibia on the femur

63
Q

describe the medial meniscus?

A

c shaped
longer than lateral meniscus
adherent to MCL thus less mobile than LCL
covers ~50% of medial articular surface of tibia (less than lateral) and thus more prone to OA

64
Q

describe the lateral meniscus?

A

u shaped
covers ~75% of tibial articular surface
no attachment to LCL thus more mobile

65
Q

explain the vascularization of the meniscus?

A

peripheral 1/3 is well vascularized, inner 1/3 not well

66
Q

what are the main function of the meniscus?

A
  • Vital for knee stability
  • Lubrification
  • Nutrition
  • Improve weight distribution
  • Reduce friction
  • Prevents excessive HE
  • Prevents capsule from getting into the jt
  • Shock absorption: protects/minimizes the amount of stress on articular cartilage
67
Q

what happens in the event of a hyperpronated foot?

A

clacaneal valgus and thus increased stress on tendon
halux valgus of 1st MTP
increased tibia and femur IR
leg appears shorter
increase in Q angle leadingh to increased lateral translation of the patella
increased stress on lateral side of PF joint

68
Q

what happens in a hyper supinated foot?

A

decreased shock absorption
increase stress in joint above
decreased tibia and femur IR

ORTHO 560 (7 decks)

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