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BIOMECH SPRING - EXAM 2 > Lecture 8 - Knee Kinematics > Flashcards

Lecture 8 - Knee Kinematics Flashcards

1
Q

What is the capsule of the knee?

A
  • Encloses med/lat TF and PF joints - multiple connective tissue reinforcements:
  • Anterior, lateral, posterior and Posterior-lateral
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2
Q

What makes up the anterior capsule of the knee?

A

Anterior: patella and tendon

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3
Q

What is the connective tissue reinforcement and muscular reinforcement of the anterior knee?

A
  • Connective tissue reinforcement: reinforced by med/lat retinacular fibers.
    (These are extensions of ITB/vastus lat & med – connections to femur/tibia/patella /quads/pat tendon/collateral ligs/menisci)
  • Muscular reinforcement: quads
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4
Q

What are the connective tissue and muscular reinforement of the lateral knee?

A
  • Connective tissue reinforcement: LCL, lat patellar retinacular fibers, ITB
  • Muscular reinforcement: biceps femoris, tendon of popliteus, lat head of gastroc
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5
Q

What are the connective tissue reinforcement and muscular reinforcement of the posterior knee?

A
  • Connective tissue reinforcement: oblique popliteal lig, arcuate popliteal lig
  • Muscular reinforcement: popliteus, gastrocs, hamstrings (esp SM)
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6
Q

What are the connective tissue reinforcement and muscular reinforcement of the posterior-lateral knee?

A
  • Connective tissue arcuate popliteal lig, LCL, popliteofibular lig
  • Muscular reinforcement: tendon of the popliteus
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7
Q

What is a fabella? Where is it?Does everyone have one?

A
  • a sesamoid bone in the posterolateral capsule of the human knee joint.
  • The presence of the fabella in humans varies widely and is reported in the literature to range from 20% to 87% [1-7]. - The fabella is located in the posterior aspect of the knee where lines of tensile stress intersect.
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8
Q

What are the 3 parts of the connective tissue reinforcement of the medial knee?

A
  • Anterior 1/3: thin layer of fascia – medial pat retinacular fibers
  • Middle 1/3: medial pat retinacular fibers, superficial and deep MCL
  • Posterior 1/3: thick – starting near adductor tubercle blending with SM tendinous expansion and posterior capsule and posterior oblique ligament. Pes anserine reinforces this.
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9
Q

What is the muscular reinforcement of the medial knee?

A
  • Muscular reinforcement: SM, SGT – pes anserine
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10
Q

What is the capsule of the knee?

A

Internal capsule lined with synovial membrane

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11
Q

How many bursa in the knee? Where?

A

14 bursae at inter-tissue junctions that encounter friction with motion
Some are extensions of synovial membrane, some external to capsule

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12
Q

What are the fat pads of the knee called?

A

suprapatellar and deep infrapatellar

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13
Q

What is the TF joint made up of?

A

TF joint: large convex femoral condyles and flat, smaller tibial plateaus

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14
Q

What do the menisci act as for the femoral condyles?

A

act as gaskets to form seats for the femoral condyles

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15
Q

Where are the menisci anchored to the intercondylar region of the tibia?

A

@ anterior/posterior horns

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16
Q

What attached the external edge of each meniscus to the tibia and the capsule?

A

coronary ligaments
- allow pivoting

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17
Q

What connects the coronary ligaments anteriorly?

A

transverse ligament

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18
Q

What do the secondary attachments of muscles to mensici help stabilize?

A
  • quads (both)
  • SM (both)
  • popliteus to lateral
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19
Q

What do the medial and lateral meniscus attach to?

A
  • Medial oval shape attaches to MCL and adjacent capsule
  • Lateral more circular, only attaches to lateral capsule, popliteus passes between LCL and lateral meniscus
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20
Q

What are the red zone and white zone of the menisci?

A

– peripheral 1/3 direct from
genicular arteries (off popliteal), this zone is called the “red zone”
- inner 2/3 avascular “white-zone” and
nutrition from synovial fluid.

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21
Q

What is the primary function of the TF joint?

A

↓ compressive forces (triples joint contact area ↓ pressure on articular cartilage

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22
Q

What is the secondary function of the TF joint?

A

stabilizing joint during motion,
lubricating articular cartilage,
providing proprioception (Mechanoreceptors
have been identified in the anterior and posterior
horns of the menisci)
Help guide arthrokinematics

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23
Q

What should we know about meniscal tears?

A

MOST COMMON
- Often associated with forceful, axial rotation of the femoral condyles over a flexed WB knee (can pinch and dislodge the meniscus)
- A dislodged or folded flap (bucket handle) can mechanically block knee motion
- Medial injured twice as frequently – valgus force (large stress on MCL/post-med capsule)
- Risk increases with ligamentous laxity (esp ACL) and malalignment

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24
Q

What mechanism do we lose with a meniscal tear?

A

Loss of hoop stress capacity with meniscal tear – especially avulsion tear at medial posterior horn

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25
Q

What are the osteokinematics of flx/ext of the knee TF joint?

A
  • 2 degrees of freedom (F/E and rot)
  • Knee slightly flexed to have rotation occur
  • Frontal plane is passive only 6-7 deg
  • Flexion/extension M-L axis in sagittal plane and it moves (IAR – ‘evolute’) within the femoral condyles
  • 130-150 and 5-10 hypertext
  • Tibial-on-femoral and femoral-on-tibia
26
Q

What is axial rotation of the knee TF joint?

A

Axial rotation: Longitudinal axis through tibia (influenced by the sagittal plane motion) little in ext…

27
Q

Whats the difference in IR / ER at the TF joint?

A

At 90 deg: 40-45 deg of axial rotation; ER 2:1 exceeds IR

28
Q

What is rotation of the knee TF joint named for?

A

Rotation named by position of tibial tuberosity relative to the anterior distal femur

29
Q

What are the arthrokinematics of tibia-on-femoral ext?

A

tibia rolls and slides anteriorly on femur; meniscus pulled anteriorly by quads

30
Q

What are the arthrokinematics of femoral-on-tibial ext?

A

femoral condyles roll anteriorly and slide posteriorly on tibia

** quads direct the roll and stabilizes the meniscus vs posterior shear of femur.

31
Q

What is “screw home” during ext of the TF joint?

A

Full ext requires 10 deg ER during last 30 deg of ext (…is linked not indep motion); increases joint congruence/stability. OC tibia ER; CC femur IR

32
Q

What is “screw home” driven by?

A

Driven by:
1. Shape of the femoral condyle (tibial follows medial condyle and creates ER)
2. Passive tension in ACL
3. Slight lateral pull of quads

33
Q

What is different about the flexion screw home mechanism?

A

Flexion is the opposite:
the unlocking IR happens
first – driven by the popliteus
(can rotate the femur or tibia)

34
Q

What are the arthrokinematics of IR/ER of the TF joint?

A
  • knee must be flexed
  • Spin between the menisci and articular surfaces of tibia and femur
  • Axial rotation of femur over tibia causes menisci to deform/compress – popliteus and SM help stabilize
35
Q

What is the shape of the MCL? regions?

A

flat and broad
Superficial and deep parts

36
Q

What should we know about the superficial MCL?

A

well-defined parallel fibers @ 10 cm med epicondyle to med pat retinaculum fibers to med proximal tibia (just posterior to pes anserine)

37
Q

What should we know about the deep MCL?

A

slightly posterior and distal: shorter and oblique attaches to capsule/medial meniscus/SM tendon

38
Q

What is the shape of the LCL? Where does it run?

A

Short cord-like
Runs vertical lateral epicondyle femur to head of fibula

39
Q

Does the LCL attach to the meniscus?

A
  • Does not attach to the adjacent meniscus (tendon of popliteus runs between them)
40
Q

What muscle tendon does the LCL blend with?

A
  • Distally it blends with tendon of biceps femoris
41
Q

What are the primary functions of the MCL and LCL?

A

function to limit motion in frontal plane
Knee extended: MCL vs valgus force, LCL vs varus force

42
Q

What are the secondary functions of the MCL/LCL?

A

Secondary function – provide general stabilizing tension (esp walking near ext and loading)
Protect against rotation extremes (MCL at extreme of ER)…ex planting R foot and body cut L.

43
Q

What are the ACL and PCL’s relation to each other?

A
  • Cross within the intercondylar notch Intracapsular, covered by extensive synovial membrane
  • Poor blood supply
  • Named for attachment on tibia, are thick and strong
44
Q

What do the ACL and PCL do as a pair?

A

Together resist extremes of all motions – but primarily A-P shear forces between tibia and femur – in sagittal plane motions, cutting (frontal and horizontal planes)
Helps guide arthrokinematics and provides proprioceptive feedback (has mechanoreceptors!!!)

45
Q

What/Where is the ACL?

A

Anterior tibia

Runs posterior, superior and lateral to medial side of lateral condyle

Collagen fibers twist on each other (2 sets – Ant Med and Post Lat)

46
Q

When are the fibers of the ACL taut?

A

At any given point some of the fibers are taut in flexion – but increasingly taut as reach ext (esp post-lat bundle - along with post capsule, knee flexor muscles, parts of the collateral ligs)

47
Q

When is the tibia pulled anterior during extension of the knee? What limits this?

A

Last 50-60 deg ext – force of quads pulls tibia ant (needed slide) and thus tension in ACL limits the slide. (>est at full ext)

48
Q

What is the anterior drawer test?

A

leg in 90 deg – pull prox tibia ant. ACL is 85% of passive resistance to ant glide 8mm or 1/3 inch > contralat LE possible tear (HS spasm may prevent good test)

49
Q

What are factors in injury of the ACL??

A

speed and direction of GRF; amount and direction of compressive and shear forces; control and timing of muscular forces; integrity and strength of tissues; alignment of trunk and lower limb

50
Q

What should we know about injury of the ACL?

A
  • Most frequently ruptured lig in the knee
  • Half in ages 15-25 – high velocity sports
  • Transient subluxation with secondary trauma (menisci, cartilage, MCL)
  • Chronic instability and further degeneration
51
Q

70% of sports related ACL injuries are …

A

70% of sports related ACL are non-contact: landing, decelerating, cutting, pivoting over single limb

52
Q

Why is hyperext also a MOI for the ACL?

A

Hyperextension also a mechanism of injury- Reduced ER and abd strength might lead to this…..

53
Q

What is the PCL?

A
  • Slightly thicker than ACL
  • Post tibia – lateral medial femur
  • 2 primary bundles
  • With flexion – twists and changes length and orientation
54
Q

When is the PCL taut? slack?

A
  • Some fibers taut in F and E – however majority of PCL becomes increasingly taut with greater flexion (90-120 >est)
  • Slack in 30/40 into ext
55
Q

What tibial glide is limited by the PCL?

A

Posterior glide – tibia (as in HS contraction) partially limited by PCL

56
Q

What is the posterior drawer test?

A
  • Prox end tibia posterior, knees in 90 deg (95% of resistance) 0-30 provides no resistance
  • Limits ant translation femur
    (rapid descent into deep squat)
  • ‘sag’ @ 90/90
57
Q

What are common MOI for the PCL?

A

high-energy trauma
Rare – 2-10% of all knee injuries
Falling onto a fully flexed knee, ‘dashboard injury’

58
Q

What is the PF joint?

A

Articular side of patella and trochlear groove
Stabilizer is quad
Chronic ant knee pain and degeneration

59
Q

What glide is important with the PF joint?

A

Tibial-on-femoral patella slide relative to fixed
trochlear groove (patella pulled in direction of tibia)
Femoral-on-tibial (squat) the trochlear groove slides
relative to fixed patella.
(held by eccentric quads and patellar tendon)

60
Q

What are the patellofemoral kinematics?

A
  • 135 deg sup pole below groove @ lat and odd facets
  • 90 deg
  • 90-60 now in trochlear groove – contact area the greatest (still only 1/3 area)
  • 20-30 contact at inf pole – has lost much of its mechanical engagement with groove (45% of that at 60 deg)
  • Full ext - rests completely prox to groove, on suprapatellar fat pad (if quads relaxed pat moves freely)

BIOMECH SPRING - EXAM 2 (5 decks)

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