Joint of the Knee

Question 1

What bones does the femur articulate with

Answer 1

Medial + lateral condyle of femur articulates with teh condyle of the tibia ( form the tibiofemoral joint)

Femir also articulates with teh patella, the seasmoid bone of the quad tendon ( forms the patallofemoral joint)

They are synovial joints, knee is a modified hinge joint with a relatively large ROM, and is most stable in extension ( closed packed position)

Question 2

Articular Surface? Describe medial and lateral condyles of the tibia and femur, which is longer in the A-P direction?

Answer 2

Medial condyle of both femur and tibia are longer than lateral in the A-P direction, medial femoral condyle projects/ more distal and bears 75 % of the weight

Question 3

What is genuvalgum & what is genuvarum?

Answer 3

Genuvalgum is the when the femur points inward even more than normal, relatively the leg is displaced more laterally

Genuvarum is the opposite it is when the femur points more outward than normal, and the weight of the limb passes more medially

Question 4

Why is the knee joint intrinsically insecure?

Answer 4

This is because the femoral condyles are round, whilst the tibial plateau is rather flat, poor congruency.

Question 5

Why is knee more susceptible to injury in flexion

Answer 5

In extension the knee joint articulations are more congruient and does not allow rotation due to the tightness of ligaments, in a flexed position there is laxity and thus rotation is allowed endangering the joint.

Question 6

Capsule of the knee joint, what does it entail?

Answer 6

It encases both tibiofemoral and patello femoral joints + various intracapsular structures such as the ACL. The synovial membranes cover everythign but articular surfaces ( intracpasular but extrasynovial)

Synovial membrane lines the margins of meniscus
ACL and PCL originate at the back moving forward, they push synovial membrane in front, hence they have synovial fluid anteriorly and laterally but not posteriorly

Question 7

Describe the pathology of synovial Joints, what is the implications of tearing a synovial joint?

Answer 7

It could result in effusion of synovial fluid ( more), or haemathrosis ( bleeding), tearing of ligament coudl take some synovial membrane too

Question 8

What is the anterior reinforcement of the Knee joint?

Answer 8

Quadricepts become the quadriceps tendon, and then terminates at the patellar tendon. The patellar releases retinacular fibres, which pass down alongside patella and terminate at the tibia.

Question 9

What is the lateral reinforcement of the knee joint capsule?

Answer 9

Illiotibial tract
popliteal muscle
Biceps femoris

Question 10

What is the medial reinforcement of the capulse of the knee? The PES Anserinus

Answer 10

From muscles which emerge at the medial apsect of the the tibia.

” Say grace before tea”

Sartorius, gracillis, bursa, semi tendonosis
Referse to insertion of muscle from top down

Question 11

What is the posterior reinforcement of the capulse of the knee?

Answer 11

THis is the oblique popliteal ligament an epansaion of the semimembranosis.

Question 12

Describe the origins & Insertions of the ACL

Answer 12

The anterior cruciate ligament originates on the angetior region of the tibia & inserts into the lateral condyle of the femur at the intercondylar notch.

Question 13

Describe the origins & insertions of the PCL

Answer 13

The posterior cruciate ligament originates at the posterior region of the tibia and then inserts into the medial condule of the femur.

Question 14

What is the function of the ACL & PCL

Answer 14

The functionof ACL & PCL is to strengthen the articulation between the femur and the tibia by resisting/ stabilising Anterior/Posterior movements

Question 15

In which direction does the ACL prevent displacement? When is the ligament taut?

Answer 15

The ACL prevents forward displacement of tibia on femur. The ligaments are taut in full flexion and full extension, loose in semi flexion ( loose packed position - when injury is most likley to occur)

Question 16

Common ACL tears, explain mechanism? Refer to how it is stabilised and taught in extension & what type of movement it allows?

Answer 16

ACL is taught in the last 15 to 20 degrees of extension & given its orientation allows some medial rotation of the femur on the tibia. When the femur however rotates laterally instead, this might cause the ACL to tear. Happens during extension on weight bearing leg

In injury, skin grafts commonly derived form middle third of the patella tendon

Question 17

In which direction does the PCL prevent dispacement?

Answer 17

It prevents posterior displacement of the tibia in knee flexion.

Question 18

Which ligament is the PCL supported by?

Answer 18

Meniscofemoral ligaments

Question 19

When is the TIbia most prone to injury?

Answer 19

Tibia is most prone to injury when we fall on a flexed knee, or there is a bumper bar injury.

Question 20

Which muscle is involved in flexion of the knee? How does it occur name origin and insertion?

Answer 20

Popliteus muscle, this muscle attaches to the proximal tubia and then to the lateral condyle of the femus pulling the femur down intiating flexion. It also intiates thus a lateral rotation of the femur, reversing the medial rotation which occured in flexion.

Question 21

Medial Collateral ligament, attachments & insertions?

Answer 21

Originates on medial femur

• Long, flat superficial part
• Deep part blends in with the capsule and attached to the medial meniscus

Question 22

What type of movement does the MCL resist?

Answer 22

• Abduction forces ( resists valgus) resists tibia flipping sideways
• Limits lateral rotation of the tibia on the femur
• Limits anterior movement of tibia on the femur, when ACL damaged

Question 23

Unhappy Triad?

Answer 23

Injury of

• MCL
• Medial meniscus
• ACL

Commonly occur due to their close relationship

Question 24

Lateral collateral ligament? Attachments? What is its function?

Answer 24

Attached to lateral epicondyle of femur

• seperated from lateral meniscus by popliteus tendon
• resists varus ( adduction forces)

Question 25

What type of cartilage is the meniscus? What its innervation and blood supply like?

Answer 25

• Fibrocartilage
• Typically receives good nerve and blood supply to peripheral outer thurd
• Good nerve supply but poor blood fibrous capsule, so its painful but takes a long time to recover

Question 26

What is the function of the meniscus

Answer 26

• shock absorbers help bear weight
• increase congruency
• increasing SA articulation which would otherwise be concentrated on the middle of the bone –> arthritic changes
• seperates joint into two cavities

Question 27

How does lateral meniscus compare in size to medial meniscus

Answer 27

Lateral meniscus is thicker, more rounded, and covers more articular surface. The lateral meniscus bears more weight than the medial meniscus but the medial tibia bears more weight than the lateral.

Question 28

Which cruciate ligament does the lateral meniscus attach to?

Answer 28

It attaches to the posterior crcuiate ligament via the meniscofemoral ligaments, which pulls it posteriorly upon flexion

Question 29

Which ligament is the medial meniscus attached to?

Answer 29

The medial meniscus is attached to the medial collateral ligament, hence movement is restricted

Question 30

Which meniscus is injured more and why?

Answer 30

Medial meniscus

• Horns are further apart
• It is longer
• It is firmly attached to medial collateral ligament (less mobile)

May be nipped or turn, longitudinal tearing –> framgent flips into joitn space causing locked knee in some flexion & difficult to extend

Question 31

What is the function of bursa?

Answer 31

• Protect tendon and ligaments against bone (reduce friction)

Question 32

Name the two communicating Bursa? Its locations & its pathologies

Answer 32

SUprapatellar bursa & semimembranosus bursa

Supra patellar bursa
- communicates with joint cavity ( fluid, pus, blood) - pathologies cause knee inflammation above the knee joitn

Semimembranosus/ popliteal bura
- lies deep to tendinous insertion of semimambranosus, beneath quadrriceps and politeus myscke.

Pathology
Bakers cyst - thickening and enlargement of bursa form excessive flexion

Question 33

Name the three non communicating bursa

Answer 33

Prepaterllar bursa
Infrapaterllar bursa
Deep infrapaterlla bursa

Question 34

What to infrapaterllar fat pads do?

Answer 34

fill out irregularities  intracapsular but extra-synovial
Pushes out and forms folds of synovial membrane = plicae

It is in between front of tibia and patella

Question 35

Patellofemoral joint, how is its normal alignment maintained

Answer 35

Strong vastus medialis muscle
medial paterllar retinacular
Raised lip on lateral femoral condule, in order to maintian the patella within the trochlear groove- prevents it from sliding laterally out of the groove

The patella can move up and down in this groove during flexion and extension.

Question 36

Talk about the pull of the quadriceps on patella

Answer 36

During flexion the quadricepts muscle pulls the patella obliquely laterally, whilst the patellar tendon will pull it vertically down, this can cause the patella to displace laterally. hence stabilised by

• vastus medialis
• raised laterla lip
• medial retinacular fibres

Question 37

What is the Q angle

Answer 37

Angle between the tendon of the quad and the patella tendon

Question 38

What makes you more susceptible to patella dislocation

Answer 38

If vastus medialis is weak

A woman due to Q angle

Question 39

Patella Dislocation, what does chrondomalacia patellae mean

Answer 39

Patella dislocation

• abnormal alignment of patella with femur
• cartilage on lateral side involved in articulartion
• cartilage degeneration occurs

Knee cap rubbing against one side of knee joitn despite there being smooth cartilage on posterior surface of patella for it to glide smoothly over surface

Question 40

Biparitite patellae

Answer 40

Patella has centre of ossificaiton with in it, two parts seperated by a growth plate. May appear as a fracture on xray