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204- MSK > Anatomy of the knee > Flashcards

Anatomy of the knee Flashcards

1
Q

What kind of joint is the knee?

What bones form its articulation?

A
  • Synovial bicondylar hinge jont
    (articulation between distal femur and proximal tibia)

+ articulation between femur and patella (fibrous joint capsule formed by a network of tendons and ligaments)

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2
Q

What are the functions of the knee

A
  • weight bearing
  • mobility (extension/flexion, some rotation when flexed)

**Incompatible functions –> frequent injury

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3
Q

State the bony and soft tissue factors which improve the stability and strength of the knee

A

BONY FACTORS
- Bony expansions, locking mechanism, femoral angle

SOFT TISSUE FACTORS
- ligaments, menisci, muscles

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4
Q

Name the bony expansions involved in the knee joint

A

FEMUR
- Epicondyles, condyles, intercondylar fossa (posterior)

TIBIA
- condyles (tibial plateau)

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5
Q

What is the first function of the locking mechanism?

How is it facilitated?

A
  • Reduces amount of energy required when extended

- Facilitated by the shape of the femur. In flexion, femoral surfaces round, in extension, femoral surfaces flat

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6
Q

The locking mechanism also facilitates rotation and acts as centre of gravity. How so?

A
  • Medial rotation of femur on tibia in extension tightens ligaments of the knee
  • Places centre of gravity in front of knee which maintains extension
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7
Q

What is the femoral angle? When does it occur?

A

Adducted femur brings knee joint under pelvis which is critical for weight bearing

  • Normal alignment of joint (mechanical axis): vertical line through centre of femoral head, centre of knee, centre of ankle
  • As opposed to anatomical axis which forms a Q angle (approx 15 degrees)

Occurs during development

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8
Q

What is varus deformity (Genu varum)?
Effect on Q angle?
Who is commonly affected?

Consequence?

A
  • Deformity in the angle between femur and tibia
  • Medial displacement of tibia
  • Pushes knees apart (bow legged)
  • Decrease in Q angle
  • Common in children<2, rickets

Increased stress at medial condyle –> joint degeneration

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9
Q

What is valgus deformity (Genu valgum)?
Effect on Q angle?
Who is commonly affected?

Consequence?

A
  • Deformity in the angle between femur and tibia
  • Lateral displacement of tibia
  • Pushes knees together (knock kneed)
  • Increase in Q angle
  • Common in children aged 2-4, rickets, arthritis

Increased stress at lateral condyle –> joint degeneration

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10
Q

What is the function of the ligaments of the knee?

State the names of the extracapsular and intracapsular ligaments

A

Provide stability

Extracapsular:
- medial and lateral collateral

Intracapsular:
- anterior and posterior cruciate

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11
Q

Describe the lateral collateral ligament

Shape
Function
Between which bony features?
Pathology

A
  • Strong round cord
  • Prevents medial displacement of tibia
  • From lateral epicondyle to fibular head. Space underneath
  • Tear of LCL = varus deformity, less common
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12
Q

Describe the medial collateral ligament

Shape
Function
Between which bony features?
Pathology

A
  • Broad flat ligament
  • Prevents lateral displacement of tibia and reinforces joint capsule (via attachment to medial meniscus)
  • Medial epicondyle and tibia
  • Tear of MCL= valgus deformity
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13
Q

Where do the anterior and posterior cruciate ligaments lie?

A
  • In intercondylar fossa of femur and intercondylar area of tibia
  • Anterior: anterior relative to tibia
  • posterior: relative to tibia
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14
Q

What is the function of the cruciate ligaments?

A

ACL- prevents anterior displacement of tibia on femur

PCL- prevents posterior displacement of tibia on femur

Together they maintain femur against tibia, always one ligament tense

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15
Q

Describe the trajectory of the cruciate ligaments

A

ACL- passes up, backwards and laterally

PCL- passes up, forwards and medially

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16
Q

In a flexed knee what does medial and lateral rotation do to the cruciate ligaments

A

Medial rotation tightens ligaments, limits rotation (10degrees)

Lateral rotation unwinds ligaments (approx 0 degrees)

17
Q

Which cruciate ligament is most prone to injury? Why?
Which kinds of injuries cause this? Result

How can you test the integrity of the ligament

A

ANTERIOR because it is weaker

  • Sports injury caused by sharp twisting of knee
  • Immediate decreased range of movement

LACHMAN TEST

  • Patient supine with knee bent to 2-30 degree flexion
  • Move tibia anteriorly and posteriorly while maintaining position of femur
  • Laxity during this manoeuvre indicates ACL injury
18
Q

When might the PCL become injured?

A

Walking down hill
- Rarely injured as stronger

It is the principle stabiliser when knee is flexed

19
Q

What are menisci?
What are their functions?
Describe the menisci of the knee joint

A
  • Crescent shape plates of fibrocartilage
  • Deepen the articulating surfaces for increased stability; shock absorbers; provide smooth viscous film for joint
  • Lateral meniscus is smalled and more circular; larger medial meniscus. Surrounded by horns of menisci
20
Q

What are the attachments of the menisci?

How does this affect mobility?

A
  • Horns of menisci attaches to intercondylar area of tibia
  • This accomodates rolling of femoral condyles

Medial meniscus less mobile as its attaches to MCL

21
Q

The unhappy triad results in rupture of which structures? Why dont they repair easily?

How do they become ruptures?

A
  • Medial meniscus
  • MCL
  • Anterior cruciate
    Poor blood supply to intracapsular structures

Twisting on a flexed knee/blow to lateral side; contacts sports; locking of knee

22
Q

What is the function of the iliotibial tract

A
  • Reinforces joint capsule

- Stabilises extended knee (glut max, tensor fascia lata)

23
Q

What are the muscles important in extension of the leg

A

Quadriceps

  • Vastus medialis
  • Vastus Intermedialis
  • Vastus lateralis
  • Rectus femoris

Major stabilizing muscle of knee

24
Q

What is the functions of the oblique fibres of vastus medialis?

A

Prevents lateral tracking of patella

25
Q

What is the function of the patella?

A
  • Protects quadriceps tendon from stresses during locomotion

- Provides a smooth oval facet for articulation with femur

26
Q

Which tendon lies superior to the patellar?

Which ligament lies inferior to the patellar?

Which structures lie medially and laterally to the patellar?

A

FORM EXTENSOR MECHANISM

  • Quadriceps tendon
  • Patella ligament
  • Medial patellar retinaculum which helps stabilise the patella
  • Lateral patellar retinaculum
27
Q

What are the main injuries to the extensor mechanism that occur?

A
  1. Rupture of quadriceps tendon or patellar ligament
  2. Fracture of patella: due to fall or blow to knee

RESULTS IN LOSS OF ACTIVE EXTENSION

  1. Dislocation of patella common- due to sudden twisting/jumping or ligamentous laxity
28
Q

What are the flexors of the leg?

A

HAMSTRINGS

  • Biceps femoris, semitendinosus, semimembranosus
    • Also medially and laterally rotate leg when knee flexed
  • Extend thigh

GASTROCNEMIUS

29
Q

What is the function of semimembranosus?

A

Reinforces joint capsule

30
Q

Which muscle is involved in unlocking knee?

What is its origin, insertion and function?

A

Popliteus unlocks the knee
- it passes through joint capsule

Origin: lateral condyle of femur
Insertion: posterior tibia

Laterally rotates femur on tibia when foot is on ground

31
Q

Outline the extent of the synovial membrane

A
  • From margins of articular surfaces of femur to tibia
  • Attached to patellar
  • Extends superiorly behind quadriceps tendons
  • Cuffs anterior surface of cruciate ligaments
32
Q

What is the function of the infrapatellar fat pad?

Where is it found?

A
  • Seperates synovial membrane from patellar ligament

- Behind patellar ligament

33
Q

What are bursae?
Function?

What are the three main bursae associated with the knee joint?

A
  • Synovial fluid filled sac lined by synovial membrane
  • Protection, reduce friction
  1. Suprapatellar bursa- continuous with synovial membrane
  2. Prepatellar bursa
  3. Infrapatellar bursa
34
Q

Where do other bursa associated with knee occur?

A
  • Occur at tendon insertions

Iliotibial tract, biceps femoris, semimembranosus, semitendinousis, gracilis, sartorius

35
Q

What is bursitis?

What is housemaids knee?

A

Inflammation of bursae due to repetitive movements or direct pressure

Prepatellar bursitis seen in carpet fitters
- leaning forward on the knees brings the prepatellar bursa in contact with floor

36
Q

What is clergyman’s knee?

A
  • Infrapatellar bursitis
  • After prolonged periods of prayer clergyman sat back on their heels bringing infrapatellar bursa in contact with floor
37
Q

What is a bakers cyst?

Amongst whom is it common?

Presentation?

Treatment?

A

Abnormal fluid filled sacs in popliteal fossa
- Due to herniation of synovial membrane/bursa
Common in patients with chronic
inflammatory joint disease (e.g. arthritis)
- Presents as swelling in the popliteal fossa
- Can affect joint movement

Treat by aspiration and cortisone injection

38
Q

What is vascular supply to the knee?

A
  • Anastomosis around knee between femoral and popliteal artery (genicular braches)
  • Limited blood supply to intracapsular structures

204- MSK (16 decks)

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