Trauma and orthopaedics (2): The knee Flashcards
Bony surfaces of the knee joint
- Condyles of femur
- Condyles of the tibia
- Patellar surface of femur
- Articular surface of patella
the distal femur anatomy
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intercondylar area
Provides attachments for the cruciate ligaments and the lateral and medial meniscus
femoral condyles vs epicondyles
Epicondyles originate above the condyles
- medial larger of two
- medial and lateral collaterals originate from respective epicondyles
Condyles
- Medial is larger than later-takes more weight
how the knee joint all comes together
Distal femur (trochlea)
Anteriorly- shallow depression for articulation with patella
- Trochlea or patellofemoral groove
- Lateral lip of trochlear groove is more prominent- resist patellar dislocation
Posteriorly- deep notch
- Intercondylar fossa
Proximal tibia
- Intercondylar eminence fits into intercondylar fossa
the patella
- Largest sesamoid bone
- Its superior aspect is attached to the quadriceps tendon, and its inferior aspect to the patellar ligament
The posterior surface of the patella articulates with the femur, and is marked by two facets:
- Medial facet: articulates with the medial condyle of the femur.
- Lateral facet: articulates with the lateral condyle of the femur.
main functions of the patella
- By enabling the quadriceps muscle to directly cross the anterior aspect of the knee and by acting as a fulcrum, the patella enhances the leverage that the quadriceps tendon can exert on the femur, increasing the mechanical efficiency of the muscle by 33-50%.
- Protection. It protects the anterior aspect of the knee joint from physical trauma.
- It reduces the frictional forces between the quadriceps and the femoral condyles during extension of the leg
the tibia
- Main bone forming the leg (shinbone)
- Expansion at proximal (medial and lateral condyles) and distal ends where it articulates at the knee and ankle
- Second largest bone in the body- weight bearing structure
Tibial plateau
Condyles form a flat surface called the tibial plateau
- Articulates with the femoral condyles
- Head of the fibula articulates with the proximal tibia at the proximal tibiofibular joint (not forming part of the knee joint)
tibial shaft has 3 borders
-
Anterior border
- Marked by the tibial tuberosity
- Insertion site for the patellar ligament
-
Posterior border
- Marked by a ridge of bone known as soleal line
- Site of origin for part of the soleus muscle
-
Lateral border
- Interosseous border
- Site of attachment for the interosseous membrane that binds the tibia and fibula together
distal tibia
- Widened due to medial and lateral malleolus → assists with weight bearing
- Articulates with tarsal bones to form part of the ankle joint
- Laterally, there is the fibular notch, where the fibula is bound to the tibia, forming the inferior tibiofibular joint.
fibula
- Located in the lateral aspect of the leg
- Attachment site for muscles rather than bearing weight
3 major articulation of fibula
- Proximal tibiofibular joint- articulates with the lateral condyle of the tibia
- Distal tibiofibular joint- articulates with the fibular notch of the tibia
- Ankle joint- articulates with the talus bone of the foot
proximal fibula
At the proximal end, the fibula has an enlarged head, which contains a facet for articulation with the lateral condyle of the tibia.
The common peroneal (common fibular) nerve winds around the posterior and lateral surface of the neck of the fibula, so is vulnerable to damage in a proximal fibular fracture.
distal fibula
Lateral surface continues inferiorly to the lateral malleolus
- The lateral malleolus of the fibula is more prominent than the medial malleolus of the tibia and can be palpated at the ankle on the lateral side of the leg
articulating surfaces of the knee
-
Tibiofemoral- medial and lateral condyles of the femur articulate with the medial and lateral tibial condyles
- Weight bearing joint
-
Patellofemoral- the patella articulates with the femur at the trochlear (patellofemoral) groove
- Both joints lined with hyalineà single joint cavity
Factors which stabilise the knee joint
- Menisci
- Capsule
- Ligaments
- Muscles
Menisci
The medial and lateral menisci (figure 4.13) are fibrocartilaginous structures in the knee that serve two functions:
- To deepen the articular surface of the tibia, increasing the stability of the joint.
- To act as shock absorbers by increasing surface area to further dissipate forces.
Menisci and collateral ligaments
In addition to the intercondylar attachments medially, the medial meniscus is attached peripherally to the medial (tibial) collateral ligament and the joint capsule. Damage to the medial collateral ligament therefore often results in a medial meniscal tear