Knee Joint, Tibiofibular Joints, Ankle Joint and Joints of the Foot

Question 1

[4-minute video]: Knee Joint dissection

Answer 1

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Question 2

Study the two femoral condyles and state which condyle:
(a) is wider transversely?
(b) has a longer antero-posterior tibial articular surface?
(c) is more curved?
(d) has a more prominent buttress?
(e) groove for insertion of the tendon of popliteus muscle?

Answer 2

(a) lateral condyle
(b) lateral condyle
(c) medial condyle (It has a more symmetrical curvature, while the lateral condyle has a sharply increasing radius of curvature posteriorly)
(d) lateral condyle
(e) lateral condyle

NOTE:
The popliteus muscle originates from the lateral condyle of the femur by a strong tendon called the popliteus tendon. This tendon courses in the groove for the popliteus muscle on the lateral aspect of the lateral femoral condyle. This muscle plays an important role in the gait cycle by initiating the flexion of the fully extended (“locked”) knee. Thus, the popliteus is referred to as the “key to unlock the knee”.

[Diagram: femoral condyles] [Diagram: popliteus]

Question 3

State the functions of the ACL.

Answer 3

● Prevent posterior displacement of the femur on a fixed tibia or anterior displacement of the tibia on the femur
● Limits posterior rolling of the femoral condyles on the tibial plateau during flexion
● Prevents hyperextension of the knee joint (this ligament is taut during knee extension)
● [Diagram] [Cadaveric image]

Question 4

State the function of the PCL.

Answer 4

It is taut during knee flexion and prevents anterior dislocation of femur on tibia, and posterior dislocation of tibia on femur.

Question 5

Name the superior and inferior attachments of the anterior cruciate ligament.

Answer 5

Superior: posteromedial surface of the lateral condyle of the femur

Inferior: anterior intercondylar area of the tibia

Question 6

Name the superior and inferior attachments of the posterior cruciate ligament.

Answer 6

Superior: anterolateral surface of medial condyle of the femur

Inferior: posterior part of intercondylar area of tibia

Question 7

Which ligaments maintain side-to-side stability of the knee joint?

Answer 7

Medial and lateral collateral ligaments

Question 8

State the key function of the:
1. medial collateral ligament
2. lateral collateral ligament

Answer 8

1. prevent valgus stability to the knee joint
2. prevent excess varus stress and posterolateral rotation of knee

Question 9

Which ligaments maintain anteroposterior stability of the knee joint?

Answer 9

The cruciate ligaments

Question 10

Describe the points of attachment of the tibial (medial) collateral ligament.

Answer 10

Superiorly: the medial condyle of the femur, just below the adductor tubercle

Inferiorly: medial condyle and medial surface of the proximal part of shaft of tibia

Question 11

Describe the points of attachment of the fibular (lateral) collateral ligament.

Answer 11

Superiorly: the lateral epicondyle of the femur

Inferiorly: the lateral surface of the fibular head

Question 12

State the significance of the intercondylar eminence of the tibia with respect to the stability of the knee joint.

Answer 12

It helps to prevent the sideways slipping of the femur on the tibia.

Question 13

State 5 factors that maintain the stability of the knee joint (other than the intercondylar eminence of the tibia).

Answer 13

1. The strength and actions of the surrounding muscles and tendons
2. The medial and lateral collateral ligaments maintain the side-to-side stability of the knee joint.
3. The cruciate ligaments maintain anteroposterior stability.
4. The iliotibial band helps in stabilizing a partly flexed knee.
5. The menisci increase the concavities of the tibial condyles for better congruence with the femoral condyles.

Question 14

Name the artery that supplies the cruciate ligaments.

Answer 14

Middle genicular artery

Question 15

Name the arteries that supply the superior tibiofibular joint, and the artery from which they branch.

Answer 15

1. the anterior and posterior recurrent tibial arteries
2. they are branches of the anterior tibial artery

Question 16

State three differences between the medial and lateral menisci of the knee joint.

Answer 16

1. The medial meniscus is semilunar in shape whereas the lateral meniscus is circular in shape.
2. The medial meniscus is attached to the medial collateral ligament whereas the lateral meniscus is attached to the tendon of popliteus.
3. The medial meniscus is more prone to injury than the lateral meniscus.

Question 17

Name three structures that pass through the oblique popliteal ligament.

Answer 17

(a) Middle genicular nerve
(b) Middle genicular vessels
(c) Posterior division of obturator nerve

Further notes:
The middle genicular nerve is a branch of the tibial nerve. It pierces the posterior capsule of the knee joint to supply the structures located in the intercondylar notch of the femur. This nerve is one of the three articular branches that arise from the upper part of the fossa, the other two being the superior medial genicular nerve and the inferior genicular nerve.

Question 18

Why is the ankle joint unstable during plantar flexion?

Answer 18

This is because the narrow posterior part of the trochlea does not fit properly in the tibiofibular mortise during plantar flexion.
(During dorsiflexion, the wider anterior part of the trochlea moves posteriorly and fits properly into the tibiofibular mortise.)
[Diagram: tenon and mortise of the ankle joint]

Question 19

State the functions of the menisci of the knee joint.

Answer 19

1. They increase the concavities of the tibial condyles for better congruence with femoral condyles.
2. They act as swabs to lubricate the joint.
3. They act as shock absorbers to protect the articular cartilage during weight transmission.
4. They adapt the varying curvatures of the femoral condyles.

Question 20

Why is the medial meniscus more prone to meniscal tears than the lateral meniscus.

Answer 20

This is because of its firm fixity to tibial collateral ligament, and greater excursion during the rotatory movements. The lateral meniscus is protected by the popliteus muscle because its medial fibres pulls the posterior horn of meniscus backward, so that it is not crushed between the articular surfaces.

Question 21

What is the unhappy triad with respect to the knee joint?

Answer 21

This refers to a combination of injury of the medial (tibial) collateral ligament, the medial meniscus and the ACL.

Question 22

State the attachments of the meniscofemoral ligaments.

Answer 22

Origin: From the posterior convexity of the lateral meniscus
Insertion: medial femoral condyle, in front and behind the posterior cruciate ligament as anterior meniscofemoral ligament of Humphrey and posterior meniscofemoral ligament of Wrisberg respectively.
[Diagram]

Question 23

What is the common name for prepatellar bursitis and how does it come about?

Answer 23

1. Housemaid’s knee
2. The superficial prepatellar bursa is located superficially between the skin and the patella. The bursa may become inflamed due to excessive friction against the patella when it comes in contact with the ground during scrubbing of the floor by a housemaid, or through similar actions. Such a bursa may get very large and drop by its weight to much below its original position. [Image: clinical presentation of prepatellar bursitis]

Question 24

What type of joint is the talocalcaneonavicular joint?

Answer 24

synovial ball and socket joint

Question 25

State the myotomes of the following movements of the knee joint:
a) extension
b) flexion

Answer 25

a) L3, L4
b) L5; S1

Question 26

State the myotomes of the following movements of the ankle joint:
a) dorsiflexion
b) plantar flexion

Answer 26

a) L4, L5
b) S1, S2

Question 27

State the functions of the patella.

Answer 27

1) Protects the quadriceps tendon against wear and tear
2) Aligns the oblique pull of the quadriceps unit, by acting as a pulley mechanism
3) Increases the mechanical advantage of the quadriceps pull, hence reducing effort

Question 28

The apex of suprapatellar bursa attaches to which muscle?

Answer 28

Articularis genu muscle
[Diagram: bursae of the knee joint] [Diagram: articularis genu muscle]

Question 29

The inflammation of subcutaneous infrapatellar bursa is called?

Answer 29

Clergyman’s knee: It is the inflammation of the subcutaneous infrapatellar bursa (subcutaneous infrapatellar bursitis). It occurs due to the friction of bursa against the tibial tuberosity due to kneeling (e.g., kneeling during prayer by Christian priests/clergymen, roofers, and floor tilers. [Image: infrapatellar bursitis clinical presentation]

Question 30

State the five major arteries that give branches that form the genicular anastomosis and list the branches from each of these arteries that participate in the genicular anastomosis.

Answer 30

(1) Popliteal artery
superior medial genicular artery, superior lateral genicular artery, inferior medial genicular artery, inferior lateral genicular artery
(2) Anterior tibial artery
anterior and posterior recurrent branches
(3) Posterior tibial artery
circumflex fibular branch
(4) Femoral artery
descending genicular artery and its branch: the saphenous artery
(5) Profunda femoris artery
descending branch of the lateral circumflex femoral artery

Question 31

Outline the formation of the genicular anastomosis.

Answer 31

📝 The superior medial genicular artery anastomoses with the inferior medial genicular artery and the descending genicular branch of the femoral artery.
📝 Besides the superior medial genicular artery, the inferior medial genicular artery anastomoses with the saphenous artery, a branch of the descending genicular artery.
📝 The superior lateral genicular artery anastomoses with the inferior lateral genicular artery and the descending branch of the lateral circumflex femoral artery.
📝 Other than the superior lateral genicular artery, the inferior lateral genicular artery anastomoses with anterior and posterior recurrent branches of the anterior tibial artery and the circumflex fibular branch of the posterior tibial artery.
📝 [3-minute video] [Diagram 1] [Diagram 2]