Anatomy of the knee

Question 1

Knee joint

Answer 1

Articulation between distal demur and proximal tibia

Synovial bicondylar hinge joint

Articulation between femur and patella

Question 2

Functions of the knee

Answer 2

Weight bearing

Mobility

• extension/ flexion
• some rotation when flexed

Question 3

Factors strengthening the joint

Answer 3

Bony factors

• bony expansion
• locking mechanism
• femoral angle

Soft tissue factors

• ligaments
• menisci
• muscles

Question 4

Bony expansions

Answer 4

Provides strong base

Epicondyles

Femoral condyles

Tibial condyles

Intercondylar fossa

Question 5

Locking mechanism

Answer 5

Shape of femur

Rotation

Centre of gravity

Question 6

Shape of femur

Answer 6

In flexion
- femoral surfaces round

In extension
- femoral surfaces flat

Question 7

Rotation

Answer 7

Medial rotation of femur on tibia in extension

Tightens ligaments of the knee

Question 8

Centre of gravity

Answer 8

Centre of gravity in front of knee

Maintains extension

Question 9

Femoral angle

Answer 9

Adducted femur brings knee joint under pelvis

Critical for weight bearing

Occurs during development

Question 10

Varus deformity

Answer 10

Deformity in the angle between femur and tibia

Medial displacement of the tibia
- common in children under 2, rickets

Bow legged

Question 11

Valgus deformity

Answer 11

Lateral displacement of the tibia
- common in children aged 2-4, rickets, arthritis

Knock kneed

Question 12

Ligaments of the knee

Answer 12

Provide stability

Two groups of strong ligaments

Extracapsular

• medial collateral
• lateral collateral

Intracapsular

• anterior cruciate
• posterior cruciate

Question 13

Lateral/ fibular collateral ligament

Answer 13

Strong round cord

Prevents medial displacement of tibia

Tear of LCL= varus deformity (medial)

Question 14

Medial/ tibial collateral ligament

Answer 14

Broad flat band

Reinforces joint capsule

Prevents lateral displacement of tibia

Tear of MCL- valgus deformity

Question 15

Intracapsular ligaments

Answer 15

Anterior cruciate ligament

Posterior cruciate ligament

Cruciate= cross shaped

Question 16

Function of cruciate ligaments

Answer 16

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

Question 17

Cruciate ligaments

Answer 17

Posterior cruciate ligament
- passes upward, forward and medially

Anterior cruciate ligament
- passes upwards, backwards and laterally

Question 18

Anterior cruciate ligament

Answer 18

Weaker- can become injured

• common sports injury
• caused by sharp twisting of knee
• immediate decreased range of movement

Lachman test
- patient in supine position with knee ben 20-30’ of flexion

Move tibia anteriorly and posteriorly while maintaining position of femur

Laxity during this manoeuvre indicates anterior cruciate ligament injury

Question 19

Posterior cruciate ligament

Answer 19

Stronger- rarely injured

Principle stabiliser when knee flexed

Question 20

Menisci of joint

Answer 20

Crescent shaped plates of fibrocartilage

Deepen the articulating surfaces/ stability

Shock absorbers

Provides smooth viscous film for joint

Question 21

Menisci attachments

Answer 21

Horns of menisci attached to intercondylar area of tibia

Mobile- accommodates rolling of femoral condyles

Medial meniscus less mobile
- attached to medial collateral ligament

Question 22

Unhappy triad

Answer 22

Twisting on a flexed knee/ blow to lateral side

Contact sports

Locking of the knee

Rupture

• anterior cruciate ligament
• medial collateral ligament
• medial meniscus

Poor blood supply to intracapsular structures so doesn’t repair easily

Question 23

Muscles acting on knee joint

Answer 23

Knee reinforced by tendons from surrounding muscles and iliotibial tract

Iliotibial tract

• reinforces joint capsule
• stabilises extended knee

Question 24

Extensors of leg

Answer 24

Quadriceps extends leg

Major stabilising muscles of the knee

4 heads

• rectus femoris
• vastus lateralis
• vastus intermedialis
• vastus medialis

Question 25

Patella

Answer 25

Protects quadriceps tendon from stresses during locomotion Smooth oval facet of posterior surface for articulation with femur

Question 26

Extensor mechanism injury

Answer 26

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

Question 27

Flexors of leg

Answer 27

Hamstrings and gastrocnemius flex leg Hamstrings are three muscles - biceps femoris - semimembranosus - semitendinosus Also medially and laterally rotates leg when knee flexed and extends thigh

Question 28

Unlocking of extended leg

Answer 28

Popliteus unlocks knee joint Laterally rotates femur on tibia when foot is on ground

Question 29

Synovial membrane

Answer 29

From margins of articular surfaces of femur to tibia Attached to patella Extends superiorly behind quadriceps tendon Cuffs anterior surface of cruciate ligament

Question 30

Bursae

Answer 30

Synovial fluid filled sac lined by synovial membrane Protection Reduce friction

Question 31

Bursitis

Answer 31

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

Question 32

Baker's (popliteal) cyst

Answer 32

Abnormal fluid filled sacs in popliteal fossa - due to herniation of synovial membrane/ bursa Common in patients with chronic inflammatory joint disease Presents as welling in the popliteal fossa Can affect joint movement

Question 33

Vascular supply

Answer 33

Anastomosis around knee Femoral artery Popliteal artery Genicular branches come from these Limited blood supply to intracapsular structures - poor repair following injury