The knee complex Flashcards
What type of joint is the knee complex?
It is a compound joint; meaning that there is more than one joint within the complex.
It is also a modified hinge joint that is most stable in extension.
There is the tibiofibular joint and the patellofemoral joint.
Where is the tibiofemoral joint and what type of joint is it?
The tibiofemoral joint is between the femur and the tibia below.
It is a weightbearing joint, with minimal bony contact (poor bony congruence). This is because the femoral condyles are round and not flat, to enable flexion and extension. The tibial condyles are flat, so the femur rolls ontop of the flat tibial condyles.
Where is the synovial membrane within the knee complex?
The synovial membrane lines only the bottom floor of the capsule, which are the tibial condyles.
The internal ligaments of the knee fuse into and arise from the synovial membrane and ripping these ligaments can result in the swelling of the knee joint.
where are the bursae within the knee complex?
There are a gazillion bursae within the knee complex, all there to prevent friction between the synovial capsule and the tendons around it.
The most popular one is the patella bursa, which sits between the front of the knee capsule and the patella tendon.
Name the major ligaments that support the knee complex?
The medial and lateral collateral ligaments; run down the medial and lateral sides of the knee complex and protect against lateral and medial sliding of the femur.
The anterior and posterior cruciate ligaments are internal ligaments that keep each side of the femur connected to the tibia below. They prevent the fibula sliding forward or backwards off the tibia.
There are transverse ligaments that run directly underneath the femoral condyles, ontop of the tibia like a carpet.
Lastly, there are the oblique and arcuate popliteal ligaments. The oblique popliteal runs within the posterior of the knee diagonally whilst the arcuate popliteal one forms a curved ācā shape along the back of the knee.
What is the unhappy triad with regards to injury of the knee?
The unhappy triad- this is when a tear of the anterior cruciate ligament results in the ripping of the medial meniscus and the medial collateral ligament. This is because the three of them are connected.
What are the tibial and fibular collateral ligaments of the knee?
The medial is sometimes called the tibial collateral and the lateral is sometimes called the fibular collateral.
The medial collateral ligament is wider and attached to the medial meniscus. It resists abduction and external rotation.
The lateral collateral ligament is shorter and seperated from the lateral meniscus by the popliteal tendon. It resists adduction .
Both are most stable in extension.
How do the cruciate ligaments function in the knee?
The anterior cruciate ligament arises from the front of the knee and inserts onto the inner back side of the capsule.
It stretches and gets tighter during extension, to prevent anterior shear forces pushing the femur forward off the tibia.
The posterior cruciate ligament arises from the back of the knee and inserts onto the front side of the capsule. It tightens during flexion to prevent the femur sliniging backwards off the tibia.
where are the menisci within the knee complex?
The menisci are fibrocartilaginous wedges that assist with weightbearing.
There are two, the medial and lateral menisci, that sit where the femoral condyles do.
The medial meniscus is part of the unhappy triad and the lateral meniscus is seperated by the popliteal tendon.
what is the blood supply of the knee?
The genicular arteries form a large anastomoses network around the knee, coming off the popliteal artery.
which muscles act upon the knee?
The quadriceps contract to extend a flexed leg, whilst the hamstrings contract to flex an extended leg.
Internal and external rotation of the leg conducted by semitendinous (medially) and biceps femoris laterally.
What is the difference between genu varum and genu valgum?
Note: the Q-angle refers to the angle formed between the femur and tibia.
Genu varum: bowleggedness. The medial condyles are squashed together and are the only ones making contact, The lateral condyles are opened and this is what is making the q-angle. This increased pressure on the medial condyle causes them to break. The tibia is abducted.
Genu valgum: Walking like a dork. The lateral condyles are the only ones making contact this time and they are the ones susceptible to breaking. The q-angle is formed by the opened medial condyles.
Where is the patellofemoral joint and how does it work?
The whole point behind the design of the patellofemoral joint was just to increase the leverage of the leg.
The quadriceps muscles contract to pull the flexed leg back down to the ground. It could do this without the patella, but the patella being there increases the leverage (force able to be exerted) on the leg.
The patella is a small, sesamoid bone embedded in the quadriceps tendon. It glides over the front of the knee with a bursa behind it.
How do the quadriceps muscles affect the patella within the quadriceps tendon?
The four muscles all insert to form the one quadriceps tendon. But rectus femoris has a tendency to pull the tendon laterally. So vastus medialis also contracts to counteract this lateral force and pull the quadriceps tendon with the patella medially again.
These two opposing forces keep the patella within the quadriceps tendon in place.
