MSK 8 - Anatomy of the Knee Joint Flashcards
What are the 4 bony surfaces that the knee joint consists of?
1) The femoral condyles
2) The tibial condyles
3) Patellar surface of the femur
4) Articular surface of the patella
NB: Fibula is not involved.
Which femoral condyle is larger?
What 2 features can be found in-between the femoral condyles?
- The medial femoral condyle is larger and takes more weight.
1) Anteriorly, there is a trochlear groove, which is more prominent on the lateral lip (a shallow depression for articulation with the patella)
2) Posteriorly, there is the intercondylar fossa
Describe the surface features of the proximal tibia (where it articulates w/the knee joint)
- You have your medial (larger) and lateral condyles, which are smooth surfaces for articulation w/the knee joint.
- A rough surface in between the condyles which is for attachment of ligaments and other structures (see slide 7)
- You can also locate the lateral and medial intercondylar tubercles + the intercondylar eminence.
What is the patella?
What does it provide to the quadriceps tendon?
- The largest sesamoid bone in the body, embedded into the quadriceps tendon
- Provides mechanical advantage when extending the knee joint
- Posterior surface is smooth for articulation with the distal femur.
Why is the knee joint not particularly stable on its own?
How is this problem overcome?
- Due to the mismatch of articulating shapes
- Overcome by tibial menisci which deepen the articular surface of the tibia and by various supporting structures (capsule, ligaments & muscles).
Describe the structure + role of the menisci in the knee joint?
Is the medial or lateral menisci more likely to be damaged + why?
- C-shaped plates of fibrocartilage that deepen the surface of articulation for stability + act as shock absorbers.
- They are wedge shaped (thicker peripherally), attached to the intercondylar area of the tibia.
- Anteriorly connected by transverse ligament of the knee.
- Medial meniscus is attached more firmly to other structures so is more likely to be damaged.
What are the 3 types of ligaments involved in the knee joint?
1) Intra-capsular (cruciate ligaments)
2) Ligaments strengthening the capsule (oblique popliteal)
3) Extra-capsular (collateral ligaments)
What are the 2 cruciate ligaments and where do they insert?
What movements do they each limit?
Which one is the strongest
1) ACL - passes anteriorly, inserts medially
2) PCL - passes posteriorly, inserts laterally
ACL (weaker) = Limits anterior movement of tibia on femur
PCL (strongest) = limits posterior movement of tibia on femure.
PCL = main stabiliser in weight bearing flexed knee,
Describe the anatomical structure of the knee joint capsule.
What is the joint capsule strengthened by?
- Surrounds the side and posterior aspect of the joint, but deficient anteriorly to allow synovial membrane to extend up beneath patella.
- Strengthened laterally and medially by fibres of the vastus lateralis/medialis.
- Strengthened obliquely by popliteal ligament (on posterior aspect)
What are the 2 main extra-capsular ligaments of the knee joint and their roles?
1) Medial collateral ligament - runs from medial femoral condyle to tibia (attaching to medial meniscus). Resists valgus forces (lateral) on tibia.
2) Lateral collateral ligament = runs from lateral femoral condyle to lateral surface of fibula head. Resists varus forces (medial) on tibia
What are bursae?
What are the 6 bursae within the knee joint?
- Bursa are fluid filled sacs with a synovial membrane which reduce friction and provide some movement around the joint.
- Suprapatellar, prepatellar, subcutaneous infrapatellar, deep infrapatellar, semimembranosus + subsartorial.
Which muscles provide knee flexion?
Hamstrings = biceps femoris, semimembranosus + semitendinosus
Assisted by gracilis, sartorius, popliteus + gastrocnemius.,
Which muscles provide knee extension?
Quadriceps femoris = rectus femoris, vastus medialis, vastus lateralis + vastus intermedius.
Think about knee extensions - 4 quad muscles being used
When can knee rotation occur?
Which muscles provide medial and lateral rotation of the knee?
- When knee is flexed, some rotation can occur (flexion + extension still the primary movements)
- Medially = Semitendinosus, semimembranosus, gracilis + sartorius
- Laterally = biceps femoris
Describe the mechanism of locking the knee in extension and unlocking in flexion.
- When locking, the femur rotates internally by 5 degrees + cruciate ligaments tighten. Knee becomes more solid column and thigh/leg muscle can relax.
- When unlocking, popliteus contracts and rotates femur laterally (externally)
- So when standing up, we lock our knee in extension, and it become unlocked upon flexion.
