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Biomechanics I > Knee > Flashcards

Knee Flashcards

1
Q

With excessive genu varum, what compartment (medial or lateral) will have increased loading?

A

Medial compartment

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2
Q

With excessive genu valgum, that compartment (medial or lateral) will have increased loading?

A

Lateral compartment

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3
Q

What are the anterior knee joint capsule reinforcements?

A
  • Medial & Lateral patellar retinacular fibers
  • Quadriceps tendon
  • Patellar tendon
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4
Q

The tendons of what muscles insert at the pes anserine? What nerve are they each innervated by?

A

S artorius F emoral N
G racilis O bturator N
T (semiTendinosis) T ibial N

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5
Q

What are the lateral knee joint capsule reinforcements?

A
  • LCL (not a part of capsule)
  • Lateral patellar retinaculum
  • IT band
  • Lateral coronary ligaments (small fibers that run vertically from lat meniscus –> tibia)
  • Biceps femoris
  • Popliteus
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6
Q

What bony landmark does the IT band and tibialis anterior insert?

A

Gerdy’s tubercle (lateral condyle of tibia)

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7
Q

What knee joint capsule reinforcements make up the posterolateral complex (PLC)?

A
  • LCL
  • Arcuate lig
  • Popliteofibular lig (head of fibular –> tendon of popliteus)
  • Popliteus tendon
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8
Q

What are the posterior knee joint capsule reinforcements?

A
  • Oblique popliteal lig (lat femoral condyle –> medial tibia)
  • Arcuate popliteal lig (fibular head –> lat femoral condyle)
  • Gastroc
  • HS
  • Popliteus
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9
Q

What are the medial knee joint capsule reinforcements?

A
  • Medial patellar retinaculum
  • MCL (part of capsule - NOT outside like LCL)
  • Medial coronary ligs (medial meniscus –> tibia)
  • Pes anserine group (Sartorius, gracilis, semitendinosus
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10
Q

T of F: the cruciate ligaments are inside the fibrous capsule but outside the synovial capsule

A

True

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11
Q

What are the names of the 4 synovial capsule outpouching (bursae) of the knee?

A
  1. Suprapatellar
  2. Popliteal
  3. Gastrocnemius (lat and med)
  4. Semimembranosus
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12
Q

What are 3 bursae of the knee that are NOT connected to the synovial capsule?

A
  1. Prepatellar bursa (in front of knee)
  2. Deep infrapatellar (behind patellar tendon)
  3. Pes anserine

When these are filled with fluid, its called extraarticular swelling since it’s outside the joint.

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13
Q

What are 2 purposes of fat pads of the knee (“Hoffa’s fat pad”)

A
  1. Protection
  2. Lubrication
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14
Q

What are plicae of the knee?

A

Synovial folds

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15
Q

What are the 4 specific plicae of the knee?

A
  1. Suprapatellar
  2. Mediopatellar
  3. Infrapatellar (ligamentum mucosum)
  4. Lateral
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16
Q

What is the clinical implication/”so what” of plicae?

A

They can become inflamed/fibrotic and be painful (plicae syndrome)

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17
Q

Which of the 4 plicae of the knee is the most problematic?
A. suprapatellar
B. mediopatellar
C. infrapatellar
D. lateral

A

B. Mediopatellar plica

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18
Q

What kind of joint is the tibiofemoral joint?

A

Bicondyloid –>
- med femoral condyle & med tibial plateau
- lat femoral condyle & lat tibial plateau

condyloid jts = 2 degrees of freedom –> for knee: sagittal plane - flex/ext, transverse plane - med/lat rot

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19
Q

What are menisci composed of?

A

Fibrocartilage

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20
Q

What purpose/functions do menisci serve?

A

-Convert relatively flat tibial plateaus to concave sockets for femoral condyles –> guides knee motion & contributes to jt stability
-Absorb shock
-Distribute force
-Lubrication of tib-fem articulation

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21
Q

How are menisci anchored to the tibia?

A
  • Ant/post meniscal horns
  • coronary ligs (meniscotibial)
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22
Q

Describe the vascularity of menisci

A

Outer 1/3: LOTS
Middle 1/3: Some
Inner 1/3: Little

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23
Q

Describe the innervation of menisci

A

Aneural except at the meniscal horns

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24
Q

What are the clinical implications of meniscal vascularity and innervation?

A

Where the tear occurs matters - does it have the vascular supply to heal? Or is surgery required? Age also matters!

25
Q

Compare and contrast the medial and lateral menisci in shape, attachments, and mobility

A

Medial:
- Shape: C
- Attachments: MCL, Semimembranosus, quadriceps
- Mobility: less

Lateral:
- Shape: O
- Attachments: popliteus, semimembranosus, quadriceps
- Mobility: greater

26
Q

Which menisci is more commonly injured?

A

Medial meniscus is more commonly injured.

27
Q

Why does the lateral meniscus have greater mobility than the medial?

A

-LCL doesn’t attach to lateral meniscus but the MCL does attach to medial meniscus
-Coronary ligs on lateral side are less dense then medial side

28
Q

Removing an entire meniscus increases peak contact pressure by ___%

A. 50%
B. 100%
C. 150%
D. 230%

A

D. 230%

29
Q

What is the MOI for meniscus?

A

ROTATION of femur over FLEXED knee in WBing

30
Q

What is the primary function of the MCL?

A

Resist external valgus force

31
Q

Based off of when the MCL is taut versus relatively slack, what motion would cause increased pain? Flex or ext?

A

Extension

32
Q

What is the primary function of the LCL?

A

Resist varus stress/force

33
Q

What is the primary purpose of the cruciate ligs: ACL and PCL?

A

Control of knee arthrokinematics

34
Q

T or F: Mechanoreceptors are present in ACL and PCL

A

True.

35
Q

Where does the ACL attach?

A

Anterior tibial spine > medial aspect of lateral femoral condyle

36
Q

T or F: the ACL has 2 portions, one that is tight in flex and one tight in ext

A

True.
Posterolateral: tightest in ext
Anteromedial: tightest in flex

37
Q

In what ways does the ACL become taught? aka how can you tear your ACL?

A
  • Ant translation of tibia on femur
  • Post translation of femur on tibia
  • End range ext
  • Extremes of varus, valgus, and tibiofemoral rot
38
Q

Assign the Quads and Hamstrings as either ACL agonist or antagonist.

A

Quads: Antagonist (quad contraction –> ant glide of tibia –> tensions ACL)
HS: Agonist (HS contraction –> post glide of tibia –> ACL on slack)

39
Q

What are the MOI for ACL?

A

Usu NON-contact (or limited):
- Rot of trunk over planted foot
- Deceleration w/ knee hyperext
Contact:
- Varus/valgus force
- Hyperext force

40
Q

Where does the PCL attach?

A

post tibia below plateau to lat aspect of med femoral condyle

41
Q

Is the ACL or PCL injured more frequently?

A

ACL

42
Q

T or F: the PCL has 2 portions, one that is tight in flex, the other in ext

A

True.
Anterolateral: more taut in flex
Posteromedial: more taut in ext

43
Q

PCL resists/becomes taut w/:

A
  • Ant translation of femur on tibia
  • Post translation of tibia on femur
  • End range FLEX
  • Extremes of varus, valgus, and rot
44
Q

Assign the Quads and HS as either PCL agonist or antagonist

A

Quads: PCL agonists
HS: PCL antagonists

45
Q

What ligament would you be concerned about for a MOI of falling onto a flexed knee w/ the foot plantar flexed (applies post force to prox tibia)?

A

PCL

46
Q

Name to extensors of the knee

A
  1. Quadriceps (rec rem, vasti group)
  2. TFL: weak (20 flex - 0 full ext)
  3. Gastroc: in closed chain ONLY (mid-late stance in gait)
47
Q

Name the primary knee flexors

A
  1. Semitendinosis
  2. Semimembranosus
  3. Biceps femoris (short & long head)
48
Q

Name knee flexor synergists (not the main knee flexors)

A
  1. TFL: weak (>20 deg flex)
  2. Popliteus
  3. Gastroc: in OKC
  4. Sartorius
  5. Gracilis
49
Q

Suppose you have an injury to the tibial nerve, how would that affect movement at the knee?

A

Decreased knee flexion strength (since the 3 primary knee flexors are innerv by the tibial n)

50
Q

Suppose you have any injury to the femoral nerve, how would that affect movement at the knee?

A

Decreased knee ext strength (since the quads are innervated by the femoral n and they ext the knee)

51
Q

How would knee flexor strength be affected by injury to:
- Tibial div of sciatic n?
- Fibular div of sciatic n?
- Femoral n?
- Obturator n?

A
52
Q

What are the functional sagittal plane motion requirements for:

  • Normal gait
  • Stairs
  • Sit to stand
A
  • Normal gait: Full ext –> 60-70 flex
  • Stairs: Full ext –> 80-85 flex
  • Sit to stand: 100-115 flex
53
Q

At what degree of flex is voluntary axial rotation motion the greatest?

A

90 deg flex

54
Q

What is the “screw home” mech of the tibiofemoral joint?

A

Mechanically involuntary coupled rotation that occurs in final 15 deg of ext –> “locks” knee in full ext

Caused by:
- Asymmetry of femoral articular surfaces
- Tension in ACL and PCL
- Lateral “pull” of quads

55
Q

In OKC, how does the tibia rotate on the femur during the screw home mech/automatic rotation into ext?

A

Tibia ext/lat rotates on femur

56
Q

In CKC, how does the FEMUR rotate on the TIBIA during the screw home mech/automatic rotation into ext?

A

Femur int/med rotates on tibia

57
Q

How does popliteus function to “unlock” the knee from a fully extended/locked position? Consider OKC and CKC.

A

OKC: int/med rot tibia on femur
CKC: ext/lat rot of femur on tibia

58
Q

What is the closed packed position of the knee?

A

Full ext
Ext/lat rot of tibia on femur (or med/int rot of femur on tibia in CKC)

59
Q

What is the loose-packed position of the knee?

A

25-30 deg flex

Biomechanics I (6 decks)

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