knee joint

Question 1

Classify the knee joint

Answer 1

Type ⇒ Synovial joint

Subtype ⇒ Modified Hinge Joint (flexion and extension around a transverse plane and slight rotation around the vertical plane)

Two components:
1. Medial and lateral femorotibial joints
2. One patella-femoral joint

Question 2

Describe the articulating surfaces of the knee joint

Answer 2

Articular surfaces:
1. Medial and lateral condyles of femur (convex) and tibia (concave).
- Fibula Medial condyle is more curved and greater in anteroposterior length.
- Fibula Lateral condyle is more massive as body weight is transmitted to the knee.
- The intercondylar notch separate the two condyles postero inferiorly (lateral wall → anterior cruciate ligament. Medial wall → posterior cruciate ligament)
- Tibia medial condyle is ovoid whereas the lateral codyle is circular → separated by the intercondylar area → two intercondylar eminences.
- Anterior and posterior horns of lateral/medial meniscus, ACL, PCL within the tibia articulating surface.

2. Articulating surface of patella from the front with the femur.
   - In standing position (extension), the patella is free from articulation
   - In fully flexed knee, the patella becomes more and more present in articulating with the femur
3. Articulating surfaces are lined by hyalie articular cartilage

Question 3

Describe the extracapsular ligaments of the knee joint

Answer 3

1. Fibrous Capsule
   - Attached proximally along the articular borders of medial and lateral femoral condyles. Attachd distally to the mragins of the tibial condyles except inferioanteriorly where it extends up to the tibial tuberosity.
   - Capsule is deficient in areas where tenons are attached like the quadriceps tendon, patella, medial and lateral patellar retinacula and ligamentum patella and posteriorly by the popliteus tendon.
2. Ligamentum patellae
   - continuation of the tendon of quadriceps femoris
3. Tibial/Medial collateral ligament
   - The medial menisus attaches to the medial collateral ligament. Extends from medial condyle of femur directed downwards and forwards to the miedal condyle.
   - Detached lower part of ischial fibers (hamstring) of adductor magnus muscle
4. Fibular / lateral collateral ligament
   - Not attached to the lateral meniscus and extends from the lateral epicondyle of femur directed downwards and backwards and attaches below to the heda of styloid process of fibula
   - Derivative of the primitive origin of peroneus longus musce.
5. Oblique popliteal ligament
   - Expansion of the tendon of semimembranosus ligament. Blends with the capsule posteriorly. Pierced by the middle genicular nerve and vessels and the genicular branch of psoterior division of obturator nerve
6. Arcuate popliteal ligament
   - Y shaped - stem from the styloid process of the head of fibula to lateral condyle of the femur and posterior part of intercondylar area of tibia.

Question 4

Describe the intracapsular ligaments of the knee joint

Answer 4

1. Cruciate ligaments (ant. / post.)
   - Intracapsular but extra synovial
   - Taut in extremes of flexion and extension

• ACL starts from anterior medial (so its movement should be diagonal) (extension). Prevents backward displacement of femur and anterior dislocation of tibia.
• positive anterior drawer test
• PCL starts from the posterior lateral (flexion). Movement and displacement prevention is same logic.
• They act as the axis for which the the femur rotates during extension and flexion.
• Prevents displacement of femur in forward/backwards movement.
• positive posterior drawer test

2. Mensci or semi lunar cartilages
   - Fibrocartilage which intervene between the condyles of femur and tibia
   - Wedge shaped plates with thick periphreal and thin inner margins ot increase the concavity of articulating surfaces.
   - Peripheral part is vascular and supplied by capsular blood vessels
   - Divides into the upper menisco-femoral and lower menisco-tibial compartment.
3. Menisco-femoral ligament
   - The horns have the ant./post. meniscofemoral ligament. (ant /post are the splitting due to the posterior cruciate ligament).
4. Transverse ligament
   - Connects the anterior horn of the medial meniscus to the anterior horn of the lateral meniscus
5. Bursae around the knee joint
   - Anterior group
   - Lateral group
   - Medial group

Question 5

locking and unlocking mechanism

Answer 5

Locking:
 Medial rotation of femur during last stages of extension when the foot is on the ground
 It brings the perfect alignment between femur and tibia (close pack position)
so that a person can stand without straining many muscles at the knee
 Locking is done by vastus medialis

Unlocking:
 Lateral rotation of femur during initial stages of flexion of the knee when the foot is on the ground
 Unlocking will make the knee free for movement
 It is done by popliteus muscle

Question 6

“unhappy triad” “terrible triad” or a “blown knee”

Answer 6

Structures involved in this injury are anterior cruciate ligament, medial meniscus and medial collateral ligament of the knee