The Knee Joint

Question 1

What is the knee joint?

Answer 1

Bicondylar modified hinge joint which is the largest synovial joint in the body, consisting of the femur, tibia and patella.
Movements: flexion, extension, internal and external rotation.

Question 2

What are the articulations of the knee?

Answer 2

Tibofemoral: articulation of the femoral condyles with the fibula

Patellofemoral: articulation of the femoral condyles with patella.

These are lined with hyaline cartilage and contained in a joint cavity.

Question 3

What is the weight bearing joint of the knee?

Answer 3

Tibiofemoral joint

Question 4

What is the role of the patellofemoral joint?

Answer 4

Allows for attachment of the quadriceps muscle for increasing efficiency for knee extension

Question 5

What is the composition of the knee capsule?

Answer 5

Outer layer is formed of fibrous connective tissue.
Inner layer is formed of the synovial membrane. It contains the patella, ligament, menisci and bursa.

Question 6

What is the bursa of the knee?

Answer 6

4 bursa are found in the knee:
Suprapatellar bursa: located superiority between quadriceps femoris and femur
Pre-patella bursa: most superficially between the skin and the apex of patella
Semimembranosus patella: located posteriorly
Infrapatella bursa which a superficial one is anterior to patella ligament and deep is posterior to patella ligament.

Question 7

What is the role of the anterior cruciate ligament?

Answer 7

Attaches from the intercondylar eminence near the medial menisci to the anteriorly to the femur,. Role is to limit anterior displacement of tibia relative to femur, providing rotational stability. It is taut in knee extension to stabilise it.

Question 8

What is the role of the posterior cruciate ligament?

Answer 8

Attaches from the intercondylar eminence of tibia posteriorly to the femur. Role is to limit posterior displacement of tibia relative to femur, providing rotational stability. It is taut in knee flexion to stabilise it.

Question 9

What is the role of the lateral collateral ligament?

Answer 9

Limits varus force on the knee when bending the knee away from the body. It has a cord-like structure which attaches from the lateral epicondyle to the head of the fibula.

Question 10

What is the role of the medial collateral ligament?

Answer 10

Limits valgus forces on the knee when in flexion towards midline, located between medial epicondyle of femur to tibia. It is attached to the medial menisci.

Question 11

Which muscles are involved in knee flexion?

Answer 11

Hamstrings formed of semitendinous, semimembranosous and biceps femoris, innervated by sciatic nerve on L4 and L5.

Question 12

Which muscles are involved in knee extension?

Answer 12

Quadriceps consisting of recuts femoris and vasta medialis and vasta lateralis, innervated by femoral nerve on L2-L4. Action of knee extension is myotome L3 and L4.

Question 13

Which muscles are involved in knee rotation?

Answer 13

Hamstrings, gracilis, sartorius, gastrocnemius, plantaris and popliteus.

Question 14

Which muscles attach to the fibula laterally?

Answer 14

Hamstrings
Biceps femoris
Lateral collateral ligament

Question 15

What is the role of the menisci?

Answer 15

Shock absorption and increases joint stability for fibulotibial articulation and synovial fluid distribution. They are located on top of the tibia and consist of medial menisci and lateral menisci, and their anterior horns are connected by transverse ligaments.

Question 16

What is the medial menisci attached to?

Answer 16

Medial collateral ligament. It is C shaped and the least mobile menisci which is more prone to tearing.

Question 17

What is the role of the menisci?

Answer 17

Act as shock absorbers
Deepen the articulation for the tibia for joint stability with tibiofemoral joint.

Question 18

What is the patella ligaments?

Answer 18

Continuation of the quadriceps tendon, formed of the recuts femoris, vastus medialis and vastus lateralis. Patella ligament engulfs patella and joins onto tibial tuberosity.

Question 19

What is genu Valgum?

Answer 19

A lateral force on the knee tears the opposite ligament being the medial collateral which is meant to limit valgus forces, causing the knees to move inwards. This generally leads to medial menisci damage.

Question 20

What is genu Vara?

Answer 20

Medial Varus force on the knee tears the opposite lateral collateral ligament, causing the knees to move outwards in a bow leg appearance. Associated with rickets which are higher in malnourished areas.

Question 21

What is the terrible triad?

Answer 21

Lateral blow to the knee results in damage to the medial menisci, resulting in tearing of the medial collateral ligament and anterior cruciate ligament.

Question 22

What are the features of the lateral menisci?

Answer 22

Lateral menisci is mobile and O-shaped, with attachments for popliteal tendon.

Question 23

How does knee locking work?

Answer 23

When in extension, the knee joint internally and medially rotates between the tibia and fibula via the quadriceps tendon to tighten ligaments of anterior cruciate, medial collateral and oblique popliteal. Tensor fascia lata and gluteus maximus act on the iliotibial band to tighten and bring the knee into hyper extension.
When foot is planted: femur internally rotates
When foot is free: tibia internally rotates

Question 24

How does knee unlocking work?

Answer 24

Popliteal muscle will:
Foot is free: internally rotate the tibia
Foot is planted: externally rotate the femur
This causes the lateral menisci to move to prevent impaction

Question 25

How does patellar subluxation occur?

Answer 25

blow to the knee causes the Quadriceps tendon to pull the patella upwards in the angle of the anterior superior iliac spine, which increases the risk of lateral patella subluxation, greater in females because of a wider pelvis. The vasta medialis of the quadriceps must be strengthened to overcome the large vasta lateralis action.

Question 26

What is the role of the iliotibial band on the knee?

Answer 26

Runs from the iliac crest to the lateral tibial condyle, receiving fibres from tensor fascia lata and gluteus maximum. Causes hyperextension

Question 27

What are the boundaries for the popliteal fossa?

Answer 27

Boundaries are formed by the semitendinosus, biceps femoris and gastrocnemius muscle. It contains the popliteal artery, popliteal vein and the tibial and common fibula nerve.

Question 28

What are the bursa in the knee?

Answer 28

Fluid filled structure in the knee which reduces friction and wear and tear, located superiorly and inferiorly both superficially/subcutaneously and deep inferiorly. Kneeling for long periods of time causes bursitis.

Question 29

What is the anterolateral ligament?

Answer 29

Attached to the tibia to limit lateral rotation. It is commonly damaged when anterior cruciate ligament is affected, causing long term rotational instability.

Question 30

How does posterior cruciate ligament rupture occur?

Answer 30

Blow to the knee in the flexed position. It is tested with the posterior draw test where leg is pulled downward while in a fixed position. Posterior sag test can also be done, comparing the level of both legs in the flexed position.

Question 31

What is the test for the anterior cruciate ligament?

Answer 31

Blow to the knee while extended
-> Anterior draw test where leg is pulled upwards and anteriorly while in fixed position.

Question 32

What is the test for the medial collateral ligament?

Answer 32

Holding patient’s leg slightly flexed against hip and medially rotating it and pulling it towards you.

Question 33

What is the test for the lateral collateral ligament?

Answer 33

Holding patient’s leg slightly flexed while you stand on inside of their leg and laterally rotate and push leg out.

Question 34

What is knee arthroscopy?

Answer 34

Used to view structures inside the knee using an arthroscope camera with a light source in order to assess damage.

Question 35

What are the static stabilisers of the knee?

Answer 35

Ligaments of the knee and the Menisci

Question 36

What are the dynamic stabilisers of the knee?

Answer 36

Muscles and their aponeuroses such as quadriceps femoris and popliteus.

Question 37

Which part of the knee is taut in extension?

Answer 37

Anterior crucial ligament.

Question 38

What is the blood supply to the knee?

Answer 38

Middle genicular artery

Question 39

What is the suprapatellar bursa?

Answer 39

AKA quadriceps bursa, Llcated betweeen the quadriceps tendon and the femur