15. Anatomy of the Knee

Question 1

Knee Joint

Answer 1

Bicondylar

Articulation between distal femur and proximal tibia

Question 2

Locking Mechanism

Answer 2

1. Shape of femur
   flexion: femoral surfaces round
   extenstion: femoral surfaces flat
2. Rotation: medial rotation of femur on tibia in extension- tightens ligaments of the knee
3. Centre of gravity
   - maintains gravity

Question 3

Femoral angle

Answer 3

femurs are slighty adducted, bringing knee joint under pelvis

critical for weight bearing

anatomical axis- follows adductions of femur

Question 4

Q angle

Answer 4

difference between anatomical axis and mechanical axis

~15degrees

Question 5

Varus deformity

Answer 5

where tibia is medially displaced relative to femur

Decrease in Q angle

‘Bow legged’

This causes increased stress which can lead to joint degeneration

tear of LCL

Question 6

Valgus deformity

Answer 6

where tibia is laterally displaced relative to femur

Increase in Q angle

This causes increased stress which can lead to joint degeneration

Tear of MCL

Question 7

Ligaments of the knee

Answer 7

Extracapsular- medial and lateral collateral- prevent valgus and varus movement

intracapsular- anterior and posterior cruciate- prevent anteroposterior movement

Question 8

Lateral collateral ligaments

aka fibular ligaments

Answer 8

Extend from lateral epicondyle to head of fibula

strong round cord

prevents medial displacement of tibia
-prevents varus deformity

Question 9

Medial collateral ligaments aka tibial ligaments

Answer 9

Extends from medial epicondyle to tibia

broad flat band
longer than lateral ligament

Prevents lateral displacement of tibia
-prevents valgus deformity
tearing this ligament is more common

Question 10

Where is the medial meniscus attached to?

Answer 10

attached to medial collateral ligament

Question 11

Anterior cruciate ligament

Answer 11

anterior in relation to tibia

• Attached to intercondylar fossa
• prevents anterior displacement of tibia relative to femur

weaker

commonly injured in sports

Question 12

Posterior cruciate ligament

Answer 12

Posterior in relation to tiba

• Attached to intercondylar fossa
• prevents posterior displacement of tibia relative to femur
• Principle stabilizer when knee is flexed

Question 13

Injury of anterior cruciate ligament

Answer 13

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

Question 14

Lachman test

Answer 14

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

Question 15

Lateral and Medial menisci

Answer 15

Lateal- smaller, more circular
Medial menisci- larger

• Deepen articulating surfaces, stability
• Shock absorbers
• Provides smooth viscous film for joint

Question 16

Medial menisci

Answer 16

Less mobile than lateral menisci

attached to medial collateral ligament

Question 17

Unhappy triad

Answer 17

blow to side of knee
sudden twisting
locking of the knee

Rupture of

• anterior cruciate ligament
• medial collateral
• medial meniscus

poor blood supply to intracapsular structures- doesnt repair easily

Question 18

Quadriceps function

Answer 18

• Extends leg
• Stabilizes muscles of the knee
• forms quadriceps tendon

Question 19

Vastus medialis oblique

Answer 19

prevents lateral trafficking of patella

Question 20

Extensor mechanism of knee

Answer 20

consists of quadriceps, quariceps tendon, patella, patellar ligament

Question 21

Lateral and medial patellar retinaculum

Answer 21

help stabilised the knee

Question 22

Patella

Answer 22

largest sesamoid bone

protects quadriceps tendon from stresses f

Question 23

Extensor mechanism injury

Answer 23

Rupture of quadriceps tendon or patellar ligament

-Fracture of patella
-Dislocation of patella (common due to sudden twisting)
results in loss of active extension

Question 24

Extensors of leg

Answer 24

Quadriceps

Question 25

Flexors of leg. What are their other functions

Answer 25

Hamstrings and gastrocnemius

medial/lateral rotation of leg when knee is flexed and extends thigh

Question 26

Gastrocnemius

Answer 26

powerful flexor of the leg at the knee joint

Question 27

Popliteus muscle

Answer 27

Unlocks knee joint

origin: tibia
inserts: lateral condyle

Laterally rotates femur on tibia when foot is on ground

Question 28

Bursae

Answer 28

fluid filled synovial sacs

protection of quadriceps tendon from sheering forces, reduce friction

suprapatellar- continuous with synovial membrane

Prepatellar

Infrapatellar bursa

Question 29

Bursitis

Answer 29

-Inflammation of bursae

• Prepatellar bursae (seen in carpet fitters)
• Infrapatellar bursitis (‘clergyman’s knee’)

-due to repetitive movements or direct pressure

Question 30

Baker’s (popliteal cyst) cyst

Answer 30

Accumulation of synovium in the poplital fossa
due to herniation or swelling of bursae

reduce movement at joint
Presents as swelling in the popliteal fossa

Treat by aspiration and cortisone injection

Question 31

Blood Supply

Answer 31

-Anastomosis around knee
femoral artery and popliteal artery

-Limited blood supply to intracapsular structures