S4L1 - Anatomy of the knee, anterior and medial thigh and femoral triangle Flashcards
What form of joint is the knee joint?
Hinge-type synovial joint. Allows for flexion and extension with a small degree of medial and lateral rotation.
What 2 articulations form the knee joint
- Tibiofemoral - medial and lateral condyles of the femur articulate with the medial and lateral tibial condyles. The weight bearing joint of the knee.
- Patellofemoral - the patella articulates with the femur at the trochlear groove.
Both joint surfaces are lined with hyaline cartilage and enclosed within a single joint cavity.
How is the efficiency of the quadriceps femoris increased?
The patella allows the tendon of the quadriceps femoris to be inserted directly over the knee, increasing the efficiency of the muscle by using the patella as a fulcrum to increase the power of knee extension.
Describe the blood supply to the knee joint.
Blood supply is by the genicular branches of the femoral and popliteal arteries.
What is the clinical relevance of the popliteal and genicular arteries?
The popliteal artery is gradually occluded by atheroma, the genicular anastomoses can dilate to maintain the blood supply to the leg.
What nerves supply the knee joint?
Nerve supply is by the nerves that supply the muscles which cross the joint. These are femoral, tibial and common peroneal nerves.
How is the stability of the knee joint improved?
- The tibial Articular surface is deepened by the menisci
2. Joint is supported by the joint capsule, ligaments and surrounding musculature.
What are the menisci?
The medial and lateral menisci are fibrocartilaginous structures in the knee. The lateral meniscus is smaller than the medial meniscus. They are crescentric (c shaped), thicker peripherally than centrally and attach at both ends to the intercondylar area of the tibia.
Medial is attached to joint capsule, intercondylar area of tibia and medial collateral ligament so immobile.
Lateral meniscus in not attached to the lateral collateral ligament so is more mobile.
What is the function of the menisci?
- 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.
What is the medial menisci connected to?
It is connected to the intercondylar area of the tibia medially.
Peripherally to the medial tibial collateral ligament and joint capsule.
How are the two menisci connected?
By the transverse ligament of the knee
How is the posterior horn of the lateral meniscus stabilised?
The posterior meniscofemoral ligament helps stabilise the posterior horn of the lateral meniscus by attaching it to the medial femoral condyle.
How are the menisci stabilised?
They are loosely attached to the joint capsule and to the tibia by coronary ligaments.
Why does healing of the menisci impair with age?
As blood supply to the menisci is from the periphery, blood flow decreased with age, and the central meniscus is avascular by adulthood, leading to impaired healing after trauma.
What are the main intracapsular ligaments of the knee joint?
The cruciate ligaments which connect the femur and the tibia and cross each other. There are two cruciate ligaments; the anterior cruciate ligament and the posterior cruciate ligament.
Describe the location of the anterior cruciate ligament
Attaches proximally to the posterolateral aspect of the femoral intercondylar fossa (medial surface of the lateral condyle) and passes distally and anteromedially to attach to the anterior aspect of the intercondylar eminence of the tibia, where it is also adherent to the medial meniscus. It resists anterior translation and medial rotation of the tibia in relation to the femur.
Describe the location of the posterior cruciate ligament
Attaches proximally to the medial border and roof of the intercondylar fossa. It passes distally and posterolaterally to attach to the posterior intercondylararea of the tibia.
What is the purpose of the posterior cruciate ligament?
The posterior crucitate ligament is the main stabiliser of the weight-bearing flexed knee and prevents the femur from sliding off the anterior edge of the tibia. Also prevents posterior dislocation of the tibia on the femur.
What does the mnemonic PAMs APpLes stand for?
Posterior passes Anterior inserts Medially
Anterior passes Posterior insert Laterally.
What is the suprapatellar bursa?
The suprepatellar bursa is located at the anterior of the knee joint where there is a deficiency in the knee capsule. Here the synovial membrane extends up beneath the patella.
What strengthens the joint capsule?
Laterally = inferior fibres of the vastus lateralis
Medially = inferior fibres of vastus medialis.
Posteriorly = oblique popliteal ligament
What are the medial and lateral collateral ligaments?
Strap like ligaments that act to stabilise the hinge motion of the knee, preventing excessive medial or lateral angulation of the tibia on the femur.
Describe the location of the medial tibial collateral ligament
A wide flat ligament found on the medial side of the joint. Proximally it attaches to the medial epicondyle of the femur, distally it attaches to the medial condyle of the tibia. It is also adherent to the medial meniscus.
The medial tibial collateral ligament resists valgus (lateral) angulation of the tibia on the femur.
What does valgus mean?
Knock knee. Lateral angulation on the tibia to the femur. The medial collateral ligament prevents this.
VaLgus = Lateral