S4: the lower limb (2)

Question 1

Why is the medial femoral condyle bigger than the lateral femoral condyle?

Answer 1

Bears more weight in the standing position because the centre of mass of the body passes medial to the knee joint

Question 2

Describe the importance of the prominent lateral femoral condyle

Answer 2

Helps prevent lateral displacement of the patella during patellar tracking

Question 3

List the functions of the patella

Answer 3

1) The patella enhances the leverage that the quadriceps tendon can exert on the femur, increasing the mechanical efficiency of the muscle
2) Protection
3) It reduces the frictional forces between the quadriceps and the femoral condyles during extension of the leg

Question 4

Name the three borders of the tibia

Answer 4

• anterior border: proximal aspect is marked by the tibial tuberosity
• posterior border: marked by a ridge called the soleal line
• lateral border: interosseous border

Question 5

What are the two articulations of the knee joint?

Answer 5

Tibiofemoral

Patellofemoral

Question 6

What are the two functions of the meniscal ligaments?

Answer 6

To deepen the articular surface of the tibia, increasing the stability of the joint
To act as shock absorbers by increasing surface area to further dissipate forces

Question 7

Where do they meniscal ligaments get their blood flow from?

Answer 7

From the periphery

Blood flow decreases with age and central meniscus is avascular by adulthood -> impaired healing after trauma

Question 8

Name the major ligaments in the knee joint

Answer 8

Intracapsular ligament: cruciate ligaments
Ligaments that strengthen the capsule: oblique popliteal ligaments
Extracapsular ligaments: collateral ligaments, patellar ligament

Question 9

Describe the orientation of the cruciate ligaments (mnemonic)

Answer 9

PAMs APpLes
Posterior passes anterior inserts medially
Anterior passes posterior inserts laterally

Question 10

Describe the oblique popliteal ligament

Answer 10

Strengthens knee joint posteriorly

Continuation of some of the fibres from semimembranosus tendon

Question 11

Describe the patellar ligament

Answer 11

Continuation of the quadriceps femoris tendon distal to the patella
Inserts onto the tibial tuberosity

Question 12

Describe the collateral ligaments

Answer 12

Stabilise the hinge motions of the knee, preventing excessive medial or lateral angulation of the tibia on the femur
MCL: resists valgus forces
LCL: resists varus forces

Question 13

What is a bursa? Name the six bursae found at the knee joint

Answer 13

Bursa = small sac lined by synovial membrane, containing a thin layer of synovial fluid
Suprapatellar, prepatellar, superficial infrapatellar, deep infrapatellar, semimembranosus bursa, subsartorial bursa

Question 14

Name the muscles which produce knee extension

Answer 14

Rectus femoris, vastus medialis, vastus lateralis, vastus intermedius

Question 15

Name the muscles which produce and assist with knee flexion

Answer 15

Produce: biceps femoris, semimembranosus, semitendinosus
Assist: gracilis, sartorius, popliteus, plantaris & gastrocnemius

Question 16

Name the muscles which lateral rotate the knee

Answer 16

Biceps femoris

Question 17

Name the muscles which medially rotate the knee

Answer 17

Semimembranosus, semitendinosus, gracilis, sartorius & popliteus

Question 18

Explain the importance of the locking mechanism of the knee

Answer 18

Knee is fully extended = ‘lock’ -> thigh and leg muscles can relax briefly without making the knee joint become unstable
Unlock = popliteus contracts, rotating the femur laterally so flexion of the knee can occur

Question 19

Name the muscles within the anterior compartment of the thigh

Answer 19

Quadriceps (4 muscles), iliopsoas, sartorius, pectineus

Question 20

Name the muscles, blood supply and innervation of the quadriceps

Answer 20

Blood supply: lateral and medial femoral circumflex arteries and the profunda femoris branch
Innervation: femoral nerve
Insertion: at the base of the patella via the tendon
Action: extend the leg at knee joint (RF flexes thigh)
Vastus lateralis = originates at greater trochanter & lateral lip of linea aspera
Vastus intermedius = originates at anterior & lateral surfaces of the femoral shaft
Vastus medialis = originates at intertrochanteric line of femur & medial lip of the linea aspera
Rectus femoris = anterior tendon originates at ASIS, posterior tendon originates at groove above acetabulum

Question 21

Name the origins, insertions, blood supply and innervation of iliopsoas, sartorius, pectineus

Answer 21

Innervation: femoral nerve (EXCEPT psoas major which is anterior rami of L1-L3)
Blood supply: lateral and medial femoral circumflex arteries and the profunda femoris branch
Iliopsoas = psoas major originates at transverse processes of the T12-L5 vertebrae & lateral margins of the intervertebral discs between them, iliacus originates at iliac fossa; insert into lesser trochanter of femur; flex the leg & laterally rotate femur
Sartorius = originates at ASIS; inserts at medial aspect of the proximal tibia; flexes, abducts & externally rotates thigh, flexes & internally rotates tibia
Pectineus = originates at pectineal line on anterior surface of superior pubic ramus; inserts into pectineal line on the posterior surface of the femur; adducts & flexes thigh

Question 22

Name the muscles, blood supply and innervation of the medial compartment of the thigh

Answer 22

Adductor magnus, adductor longus, adductor brevis, gracilis, obturator externus
Action: adduct thigh
Innervation: obturator nerve
Blood supply: obturator artery and vein
Adductor magnus (only adductor portion) = originates at inferior ramus of pubis; inserts onto linea aspera of femur; also flexes thigh
Adductor longus = originates at body of pubis; inserts onto middle 1/3 of linea aspera of femur
Adductor brevis = originates at body of pubis & inferior pubic ramus; inserts into linea aspera of the femur
Gracilis = originates at body of pubis & inferior pubic ramus; inserts into medial surface of proximal tibia; flexes leg at knee
Obturator externus = originates at external surface of obturator membrane; inserts into posterior aspect of greater trochanter; laterally rotates thigh

Question 23

What are the three borders of the femoral triangle and what does it contain?

Answer 23

Superior border = inguinal ligament
Lateral border = sartorius muscle
Medial border = medial border of adductor longus
Contains femoral canal (deep lymph nodes & vessels), femoral nerve, femoral artery, femoral vein

Question 24

What are the four borders of the femoral canal?

Answer 24

Medial border = lacunar ligament
Lateral border = femoral vein
Anterior border = inguinal ligament
Posterior border = pectineal ligament

Question 25

What are the three borders of the adductor canal?

Answer 25

Anterior = sartorius
Lateral = vastus medialis 
Posterior = adductor longus & magnus