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BSMS204 Theme 2 Musculoskeletal > 15. Anatomy of the knee > Flashcards

15. Anatomy of the knee Flashcards

1
Q
A
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2
Q

Functions of the knee

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3
Q

Factors strengthening the joint

A

Several factors help improve stability and strength:

Bony factors

  • Bony expansions
  • Locking mechanism
  • Femoral angle

Soft tissue factors

  • Ligaments
  • Menisci
  • Muscles
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4
Q

Bony expansions

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5
Q

Locking mechanism

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Reduces amount of energy required when extended

3 components:

  1. Shape of femur
  2. Rotation
  3. Centre of gravity
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6
Q
  1. Shape of femur
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7
Q
  1. Rotation
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Medial rotation of femur on tibia in extension

  • Tightens ligaments of the knee
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8
Q
  1. Centre of gravity
A

Centre of gravity in front of knee

  • Maintains extension
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9
Q

Femoral angle

A
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10
Q

Varus deformity (Genu varum)

A

Deformity in the angle between femur and tibia

Medial displacement of the tibia

  • Common in children under 2, rickets

Pushes knees apart - ‘Bow-legged’ = Decrease in Q angle

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11
Q

Valgus deformity

A

Lateral displacement of the tibia

  • Common in children aged 2-4, rickets, arthritis

Brings knees together - ‘Knock-kneed’ = increase in Q angle

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12
Q

Ligaments of the knee

A

Provide stability

Two groups of strong ligaments:

Extracapsular – outside capsule

  • Medial collateral
  • Lateral collateral

Intracapsular – inside capsule

  • Anterior cruciate
  • Posterior cruciate
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13
Q

Lateral/fibular collateral ligament

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14
Q

Medial/tibial collateral ligament

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15
Q

Intracapsular ligaments

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16
Q

Function of cruciate ligament

A

Anterior cruciate

  • Prevents anterior displacement of tibia on femur

Posterior cruciate

  • Prevents posterior displacement of tibia on femur

Maintain femur against tibia

  • Always one ligament tense
17
Q

Cruciate ligaments

A
18
Q

Anterior cruciate ligament

A

Weaker - can become injured

  • Common sports injury
  • Caused by sharp twisting of knee
  • Immediate decreased range of movement

Lachman test (variation of Drawer test):

  • Patient in supine position with knee bent 20-300 of flexion
  • Move tibia anteriorly and posteriorly while maintaining position of femur
  • Laxity during this manoeuvre indicates anterior cruciate ligament injury
19
Q

Posterior cruciate ligament

A

Stronger - Rarely injured

  • Principle stabilizer when knee flexed

(Especially when walking down hill)

20
Q

Menisci of joint

A

Crescent-shaped plates of fibrocartilage

  • Deepen the articulating surfaces/stability
  • Shock absorbers
  • Provides smooth viscous film for joint
21
Q

Menisci attachments

A

Horns of menisci attached to intercondylar area of tibia

Mobile - Accommodates rolling of femoral condyles

Medial meniscus less mobile

  • Attached to medial collateral ligament
22
Q

Unhappy triad

A

Twisting on a flexed knee/blow to lateral side

Contact sports (rugby tackle)

Locking of the knee

Rupture:

  • Anterior cruciate ligament
  • Medial collateral ligament
  • Medial meniscus (attached to MCL)

Poor blood supply to intracapsular structures

Doesn’t repair easily

23
Q

Muscles acting on knee joint

A

Knee reinforced by tendons from surrounding muscles and iliotibial tract

Iliotibial tract

  • Reinforces joint capsule
  • Stabilizes extended knee
  • (gluteus maximus, tensor fascia lata)
24
Q

Extensors of leg

A

Quadriceps extends leg

Major stabilizing muscle of the knee

4 heads:

  • Rectus femoris
  • Vastus lateralis
  • Vastus intermedialis
  • Vastus medialis
25
Q

Quadriceps femori

A
26
Q

Extensor mechanism

A
27
Q

Extensor mechanism injury

A

Rupture of quadriceps tendon or patellar ligament

Fracture of the patella

  • Due to fall or blow to knee
  • Results in loss of active extension

Dislocation of patella common

  • Due to sudden twisting/jumping or ligamentous laxity
28
Q

Flexors of leg

A

Hamstrings and gastrocnemius flex leg

Hamstrings actually three muscles:

  • Biceps femoris
  • Semimembranosus
  • Semitendinosus

Also medially and laterally rotates leg when knee flexed

And extends thigh

29
Q

Hamstrings

A
30
Q

Unlocking of extended leg

A

Popliteus unlocks knee joint

  • Laterally rotates femur on tibia when foot is on ground
31
Q

Synovial membrane

A

From margins of articular surfaces of femur to tibia

Attached to patella

Extends superiorly behind quadriceps tendon

Cuffs anterior surface of cruciate ligaments

32
Q

Bursae

A

Synovial fluid filled sac lined by synovial membrane

  • Protection
  • Reduce friction

Many bursae associated with the knee

occur at tendon insertions

33
Q

Posteriolateral and posteriomedial aspects of knee

A
34
Q

Bursitis

A

Inflammation of bursae

  • Due to repetitive movements or direct pressure

Prepatellar bursitis (‘housemaid’s knee’)

  • Seen in carpet fitters

Leaning forward on the knees brings the prepatellar bursa in contact with floor

35
Q

Infrapatellar bursitis

A

(clergyman’s knee’)

After prolonged periods of prayer clergymen sat back on their heels bringing infrapatellar bursa in contact with floor

36
Q

Popliteal/Baker’s cyst

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

37
Q

Vascular supply

A

Anastomosis around knee

  • Femoral artery
  • Popliteal artery

Limited blood supply to intracapsular structures

  • Poor repair following injury

BSMS204 Theme 2 Musculoskeletal (22 decks)

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