Anatomy- Knee and Leg Flashcards
What bones comprise the knee joint?
- Femoral condyles
- Tibial condyles
- Patella
What 3 articulations are formed by the knee joint?
- 2 femorotibial
- 1 femeropatellar
Is the fibula associated with the knee joint?
NO
What is the role of the fibula and what articulations does it make?
- Plays little role in weight bearing and is an important site for muscle attatchments and also stabilises the ankle.
- Articulates with tibia at tibiofemoral joint
What is the allignment of the femur on the tibia like and why is this important?
- Femur is diagonal whereas tibia is vertical
- There is a Q angle between the two
- Allows knee to be positioned under the hip and distributes weight evenly across knee
- Retains centre of gravity to midline
What does the obliquety of the femur depend on?
-Depends on angle of alignment normally around 126 degrees between neck and shaft of femur.
What degrees is the Q angle usually?
around 15
but is greter in females
How can Q angle be measured?
-By drawing line from ASIS to middle of patella then a vertical line through patella and tibial tuberosity and calculating angle between them.
What is genu varum?
- When Q angle is less than 17 degrees
- Tibia adducted with respect to femur
- Bow leg
What is genu valgum?
- When Q angle is more than 17 degrees
- Tibia abducted with respect to femur
- Knock knee
Describe the stability of the knee joint and what helps to provide it?
-Not very stable, most stable when extended
-Depends on: ligaments connecting femur and tibia
Strength of its surrounding muscles (and their tendons)
What are the inner articular ligaments and where are they?
- ACL
- PCL
- Cross each other obliquely in the centre of the knee
Which of the CL ligaments is stronger?
-Posterior
Where exactly are the ACL and PCL (origins and insertions)?
- ACL: attaches to ant. intercondylar region of tibia and travels superoposteriorly to attach to lat. femoral condyle.
- PCL: attaches to post, intercondylar regions of tibia and travels superoanteriorly to insert onto medial femoral condyle.
What is the function of the ACL?
- Prevents ant. displacement of the tibia on the femur
- Prevents hyperextension
What is the function of the PCL?
- Prevents post. displacement of the tibia on femur
- Prevents hyperflexion of knee
- Main knee stabiliser when weight bearing eg. walking down hill
What are the menisci?
-2 crescent shaped fibrocartilage joints between femur and tibia
Where are menisci thicker?
At external margins
What is the function of the menisci?
- Increase joint congruency
- Shock absorbing
- Distribute weight evenly
- Assist in locking mechanism
- Aid lubrication by facilitating movement of synovial fluid
What are meniscal tears and what may cause them?
- May be due to sports injury or degenerative changes
- Displaced cartilage can become trapped during knee movements (pain or locking)
What is a potential treatment for meniscus tears and a risk associated?
-Menisectomy (associated with development of osteoarthritis)
When may ACL damage occur and how can it be tested?
- When knee is hyperextended or force applied anteriorly
- Test: tibia can be pulled anteriorly on a fixed femur
When may PCL damage occur and how may it be tested?
- When landing on the tibial tuberosity with the knee flexed.
- Test: tibia can be pushed post. on a fixed femur
What muscles are involved in stabilising the knee joint and what is the mosst important?
- Quadriceps, hamstrings, sartorius, gracilis, IT tract
- Quads most important, building up that muscle can even compensate for ligament damage
What is an arthroscopy?
-A minimally invasive technique that can be performed under local anaesthetic and allows inspection and surgical repair of ligaments and menisci
What are the extra articular ligaments of the knee joint and what is their common role?
- Fibular (lateral) collateral ligament
- Tibial (medial) collateral ligament
- Both prevent rotation during extension of the knee contributing to stability while standing
Describe the fibular collateral ligament location and structure and function?
- Cord like band
- Prevents adduction of the leg at the knee
- Not attatched to lateral meniscus
Describe the tibial collateral ligament location, structure and function?
- Flat band
- Attatches to medial meniscus
- Prevents abduction of leg at knee
What is combined knee injury and how may it be caused?
- Caused by lateral excessive twisting of the flexed knee or blow to lateral side of extended knee
- Abduction of leg ruptures medial collateral ligament, rotation ruptures ACL
- Injures ACL, collateral ligaments and may also tear menisscus
How may combined knee injury be treated?
-Would need surgical reconstruction of ligaments, attempting to save as much of menicus as possible.
What is knee bursa?
-Knee surrounded by bursa to allow free movement of skin and surrounding ligaments and tendons.
What are the most commonly involved bursa around the knee?
- Prepatellar
- Infrapatellar
- Suprapatellar
What is the largest of the knee bursas and describe its location?
- Suprapatellar and is continous with synovial cavity of knee.
- Is held in place by articularis genus muscle (part of vastus intermedius).
How may patella dislocation occur?
- Large Q angle and strong quad contraction can cause it because:
- Greater the Q angle, the greater the tendancy to move the patella laterallt againt lateral femoral condyle.
- Rectus femoris, vastus intermedius and lateralus all pulling superolaterally.
What movements occur at the knee joint?
- Flexion varied ammounts depending on whether hip is extneded or flexed or passive
- Medial rotation
- Lateral rotation
Describe the process of locking the knee and unlocking the knee?
- As joint approaches full extension, femur undergoes a few degrees of med. rotation on tibia.
- This is called locking the knee (it is very stav=ble and allows the thigh to relax)
- Knee unloocked by politeus muscle which laterally rotates femur
What are the borders of the popliteal fossa?
- Superomedial: semimembranosus
- Superolateral: biceps femoris
- Inferomedial: med. head of gastrocnemius
- Inferolateral: lat. head of gastrocnemius and plantaris
- Floor: post. surface of knee joint
What are the contents of the popliteal fossa?
- Popliteal artery and vein
- Tibial nerve
- Common fibular nerve
