Week 5: Menisci & Knee Joint Motion Flashcards
Describe the shape of the medial and lateral menisci when viewed from above:
- Medial: Larger and more oval (C shaped) than the lateral menisci
- Lateral: Nearly circular
What are the specific attachment sites of the medial meniscus?
- Anterior horn: Anterior intercondylar area of tibia in front of the ACL
- Posterior horn: Posterior intercondylar area in front of the PCL
- Margin: To joint capsule & deeper fibers of the MCL
What are the specific attachment sites of the lateral meniscus?
- Anterior horn: Anterior intercondylar area lateral to and behind attachment of ACL
- Posterior horn: Posterior intercondylar area in front of the end of the medial meniscus
- Margin: To joint capsule
What is the unhappy triad?
Trauma to the knee joint which results in injury of the medial meniscus, MCL and ACL
What is the role of the coronary ligaments?
Attaches menisci to the margins of the tibial plateau and to the knee joint capsule
Describe the shape of the menisci when viewed in the coronal plane:
Wedge shaped; thicker at their external margins and taper to thin unattached edges in the interior of the joint
Why are the upper surfaces of the menisci slightly concave?
Deepen the articular fossae for the reception of the convex femoral condyles
What are some of the functions of the menisci?
- Distribution of loads
- Improve congruence
- Aid in stability of the joint/shock absorption
- Aid in distribution of synovial fluid (joint nutrition)
Describe the vascular supply to the menisci and the implications of this supply to healing:
Outer 1/3 well vascularised, therefore tears to the inner 2/3rds do not heal well
Describe the gross structure and function of the transverse ligament:
- Band of transverse fibres joining the anterior horns of the menisci
- May be absent, or sometimes a second intermeniscal ligament is present at the posterior horns
Describe the motion of the femoral condyles relative to the tibial articular surfaces (arthrokinematics) during extension and flexion (osteokinematics) at the knee joint:
- Extension:
Femoral condyles roll anteriorly and translate posteriorly - Flexion:
Femoral condyles roll posteriorly and translate anteriorly
Why do the menisci move slightly forward during extension of the knee joint?
The femoral condyles (passively) push the menisci forwards during extension and
surrounding ligaments also contribute to pulling the menisci anteriorly
Why do the menisci move slightly backward during flexion of the knee joint?
They are pulled posteriorly via attachments to muscles which contract – popliteus (lateral), semimembranosus expansion (medial)
What ligametn attaches the meniscus to the patella?
Patellomeniscal/meniscopatellar ligament