l15:anatomy of the knee

Question 1

what is the articulation between the distal femur and proximal tibia

Answer 1

The knee aka synovial bicondylar hinge joint

Articulation between femur and patella

Question 2

what are the functions of the knee

Answer 2

-Weight-bearing

• Mobility
• -extension/flexion
• -some rotation when flexed

Question 3

what are the different factors that help improve stability and strength

Answer 3

Bony factors:

• Bony expansions
• Locking mechanism
• Femoral angle

Soft tissue factors:

• Ligaments
• Menisci
• Muscles

Question 4

go over bony expansions and what they provide for the leg

Answer 4

intercondylar fossa

tibial condyles

epicondyles

femoral condyles

Provides a strong base

Question 5

locking mechanism 1: describe the shape of the femur

Answer 5

• in flexion:- femoral surfaces round

- in extension- femoral surfaces flat

Question 6

locking mechanism 2 : describe rotation of the knee

Answer 6

Medial rotation of femur on tibia in extension

- Tightens ligaments of the knee

Question 7

locking mechanism 3 :describe the centre of gravity

Answer 7

Centre of gravity in front of knee

- Maintains extension

Question 8

what is the importance of the femoral angle

Answer 8

Adducted femur brings knee joint under pelvis

Critical for weight bearing

Occurs during development

Question 9

what is the femoral angle made up of

Answer 9

• anatomical axis
• mechanical axis
• forming the Q angle

Question 10

what is the normal alignment of the knee

Answer 10

Normal alignment of joint (mechanical axis) :
Vertical line through centre of femoral head,
centre of knee and centre of ankle

Question 11

what is the anatomical axis and mechanical axis

Answer 11

Anatomical: follows Asis

mechanical: vertical line through centre of femoral head, centre of knee and centre of ankle

where weight and force are distributed

Question 12

describe the varus deformity Genu Varum

Answer 12

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

caused by increased stress which causes joint degeneration

Question 13

describe Valgus deformity (Genu valgum)

Answer 13

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

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

the stress also results in joint degeneration

Question 14

what are the ligaments of the knee

Answer 14

2 groups:

Extracapsular – outside capsule

	- Medial collateral 
	- Lateral collateral

&

Intracapsular – inside capsule

	- Anterior cruciate
	- Posterior cruciate

Question 15

describe the lateral/fibular collateral ligament

Answer 15

Strong round cord

- Prevents medial displacement of tibia

Question 16

what does a tear in the LCL cause

Answer 16

Tear of LCL = Varus deformity (medial)

Question 17

describe the Medial/tibial collateral ligament

Answer 17

Broad flat band

• Reinforces joint capsule
• Prevents lateral displacement of tibia

Question 18

what does a tear of the MCL cause

Answer 18

= Valgus deformity (lateral)

Question 19

what is the intracapsular ligament

Answer 19

divided into the anterior cruciate ligament

• posterior cruciate ligament
• anterior and posterior in relation to tibia

Question 20

what is the function of the posterior and anterior cruciate

Answer 20

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 21

describe the cruciate ligaments

Answer 21

look at slide 16

Question 22

what is the Lachman test

Answer 22

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 23

what happens with the weakness of Anterior cruciate ligament

Answer 23

Weaker - can become injured

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

Question 24

does the posterior cruciate ligament

Answer 24

Stronger - Rarely injured

• Principle stabilizer when knee flexed

Question 25

describe the menisci of the joint

Answer 25

Crescent-shaped plates of fibrocartilage - Deepen the articulating surfaces/stability - Shock absorbers - Provides smooth viscous film for joint

Question 26

what are the menisci attachments

Answer 26

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 27

what is the unhappy triad

Answer 27

``` 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) ```

Question 28

what is the iliotibial tract

Answer 28

Iliotibial tract - Reinforces joint capsule - Stabilizes extended knee (gluteus maximus, tensor fascia lata)

Question 29

what muscles are involved in extension of the leg

Answer 29

Quadriceps extends leg Major stabilizing muscle of the knee 4 heads - Rectus femoris Vastus lateralis Vastus intermedialis look at slide 24 Vastus medialis

Question 30

what is the extensor mechanism

Answer 30

Patella - Protects quadriceps tendon from stresses during locomotion - Smooth oval facet of posterior surface for articulation with femur - Lateral patellar retinaculum - Medial patellar retinaculum

Question 31

what is the extensor mechanism injury

Answer 31

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 32

what are the flexors of the leg

Answer 32

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

Question 33

describe unlocking of extended leg

Answer 33

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

Question 34

what is the synovial membrane

Answer 34

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

Question 35

describe the bursae

Answer 35

Synovial fluid filled sac lined by synovial membrane - Protection - Reduce friction

Question 36

describe other bursae

Answer 36

32

Question 37

describe bursitis

Answer 37

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 38

describe Infrapatellar bursitis (‘clergyman’s knee’)

Answer 38

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

Question 39

describe the Bakers (popliteal) cyst

Answer 39

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

Question 40

describe the vascular supply

Answer 40

Anastomosis around knee - Femoral artery - Popliteal artery Limited blood supply to intracapsular structures - Poor repair following injury