Anatomy of knee

Question 1

Knee joint articulation description

Answer 1

Articulation b/w distal femur and proximal tibia [tibiofemoral]
- Articulation between femur and patella [patellofemoral]

Joint type
- Synovial bicondylar hinge joint

Question 2

Factors that stabilise the knee joint

Answer 2

Bony

• Locking mechanism
• Bony expansion
• Femoral angle

Soft tissues

• Ligaments
• Muscles
• Menisci

Question 3

Locking mechanism

Answer 3

Aims to reduce the amount of energy required when knee is extended.

Features:
1. Femur is round in flexion and flat in extension.

2. The femur medially rotates into tibia during extension= tightens ligament
3. Centre of gravity anterior to knee= maintains extension

Question 4

Q angle

Answer 4

Angle between anatomical and mechanical axis

• Normal = 15 degrees
• Larger in females due to wider pelvic bone

Question 5

Anatomical and mechanical axis

Answer 5

Anatomical axis
- Line through greater trochanter to patella

Mechanical axis

• Line through centre of femoral head, central knee and central ankle
• Key for weight bearing

Question 6

Varus deformity

Answer 6

Bow leg
- Medial displacement of the tibia= decrease in Q angle

Increases stress on medial condyle of femur and tibia—>
lead to joint degradation.

Causes: Age<2, rickets, LCL tear

Question 7

Valgus deformity

Answer 7

Knocked knees
- Lateral displacement of the tibia= increases the Q angle

• Increases stress on the lateral condyle of femur and tibia.

Causes: arthritis, age 2-4, rickets, MCL tear

Question 8

Medial [tibial] collateral ligament

Answer 8

Between medial epicondyle of femur and tibia.

• Prevents lateral displacement of knee
• Connects directly to middle meniscus
• Weaker, more commonly torn–> valgus deformity

Question 9

Lateral [fibular] collateral ligament

Answer 9

Between lateral epicondyle and fibular head.

Prevents medial displacement of the knee [prevents varus deformity]

Very strong, injury is less common than MCL.

Question 10

Anterior cruciate ligament

Answer 10

Between lateral intercondylar fossa of femur and medial intercondylar area of tibia.
- passes upwards, backward and laterally

• Prevents anterior displacement of the tibia on femur

Question 11

Function of cruciate ligaments

Answer 11

Prevents anterior and posterior displacement of tibia on fibula.

When knee is flexed

• Allows medial rotation by tightening [limited]
• Allows lateral rotation by loosening [60 degrees]

Question 12

Posterior cruciate ligaments

Answer 12

Between medial intercondylar fossa of femur and lateral intercondylar area of tibia.
- Passes upwards, forwards and medially.

Prevents posterior displacement of the tibia
- rarely injured

Question 13

Lachman test

Answer 13

Test that assesses ACL injury

Patient is in supine position, with knee flexed slightly.

Tibia moved anterior and posterior, with femur held still.
- Laxity indicates ACL injury

Question 14

Menisci of joint

• Description
• Function

Answer 14

Fibrocartilage

• Lateral and medial
• Horn attach to intercondylar area of tibia

Function

• Deepens the articulating surfaces= stability
• Shock absorption
• Lubrication

Question 15

Medial meniscus

Answer 15

Larger of the two

- Connected directly to the MCL [Popliteus ligament passes between]

Question 16

Unhappy triad

Answer 16

Rupture of the MCL, MCL and medial meniscus

• Due to twisting of a flexed knee/ blow to lateral side
• Intracapsular ligaments does not heal easily due to poor blood supply.

Causes
- Contact sports [i.e rugby tackle]

Question 17

Iliotibial tract

Answer 17

Thickening of fascia lata
- From gluteus Maximus, tension fascia lata

Stabilises the extended knee laterally

Question 18

Action of extensors on knee

Answer 18

Quadriceps

• Rectus femoris
• Vastus lateralis
• Vastus medialis= medial fibres pull medially to prevent lateral tracking of the patella
• Vastus intermedialis

Question 19

Patella retinaculum

Answer 19

Medial and lateral

- Stabilises the patella.

Question 20

Flexors of the leg on the knee

Answer 20

Hamstrings and gastronemius

Hamstrings

• Biceps femoria
• Semimembranous
• Semitendinosus

Medially and lateral rotates leg when knee is flexed

Extends thigh

Question 21

Hamstrings

Answer 21

Biceps femoris

Semimembranosus
- Reinforces joint capsule

Question 22

Popliteus muscle

Answer 22

Passes through joint capsule
- Between MCL and medial meniscus

Unlocks the knee joint by laterally rotating the femur on the tibia

Question 23

Synovial membrane

Answer 23

Margins the articular surfaces of femur to tibia

Attached to patella

Cuffs anterior surface of cruciate ligaments

Question 24

Bursae

Answer 24

Synovial fluid filled sac, lined by synovial membrane
- Between tendon and bone

Protects tendon, reduces friction

3

• Suprapatellar
• Prepatellar
• Infrapatellar

Question 25

Bursitis

Answer 25

Inflammation of bursae due to repetitive movements/ direct pressure.

Question 26

Prepatellar bursitis

Answer 26

Inflammation caused by leaning forward on knees.

Question 27

Infrapatellar bursitis

Answer 27

Inflammation caused by continuous sitting back on heels bringing infrapatellar bursa in contact with floor

Question 28

Baker’s cyst

Answer 28

Popliteal cysts
- Fluid filled sacs caused by herniation of synovial membrane/ bursa

cause

• arthritis
• other chronic inflammatory joint disease

Presents
- Swelling in fossa

Question 29

Vascular supply of knee

Answer 29

Anastomosis from popliteal artery and femoral artery.
- Genicular branches

Limited blood supply to intracapsular artery