Knee joint Flashcards
Which articulation is the weight bearing joint of the knee
Tibiofemoral - particularly medial condyle as it is larger
What lines the articulating surfaces
Hyaline cartilage
Patella is formed inside which tendon
Quadriceps femoris (main knee extensor) tendon which inserts directly over the knee, increasing the muscle’s efficiency
What is between the femoral condyles and what is the significance
Anteriorly - shallow depression to allow knee articulation
Posteriorly - intercondylar fossa
Significance of femoral epicondyles (above condyles)
Site of attachment for collateral ligaments
Medial epicondyle of femur has adductor tubercle (insertion of hamstring part of adductor Magnus)
Describe surface of tibia
Medial surface is concave
Lateral surface is convex
Medial and lateral surfaces are separated by intercondylar eminence
What strengthens the knee joint
Menisci,
Ligaments,
Capsule,
Muscles
How does the menisci strengthen the knee joint
Deepens the articulation (of tibial element)
Act as shock absorbers
Features and attachments of menisci
Crescentric plates of fibrocartilage,
Thicker at edges (wedge shaped),
Attached to intercondylar areas,
Attached to joint capsule via coronary ligaments,
Anteriorly connected (medial and lateral menisci) by transverse ligament of knee
What intracapsular ligaments are involved in the knee joint
Anterior cruciate ligament,
Posterior cruciate ligament
How are cruciate ligaments named
Attachment to tibia
Course of anterior and posterior cruciate ligaments
Posterior passes anteriorly and inserts medially (posterior intercondylar region of tibia to femoral intercondylar fossa)
Anterior passes posterior and inserts laterally (anterior intercondylar region of tibia to femoral intercondylar fossa)
Pam’s apples!
Features of anterior cruciate ligament
Weaker than posterior cruciate ligament,
Relatively poor blood supply,
Limits anterior movement (prevents anterior dislocation) of tibia on femur,
Limits knee hyperextension
Features of posterior cruciate ligament
Stronger than anterior cruciate ligament,
Main stabiliser in weight bearing flexed knee,
Limits posterior movement (prevents posterior dislocation) of tibia on femur,
Limits knee hyperflexion
Where is joint capsule absent and why
Anteriorly
Allows synovial membrane to extend up beneath patella
How is the joint capsule strengthened laterally
Inferior fibres of vastus lateralis and medialis
How is the joint capsule strengthened posteriorly
Oblique popliteal ligament (an expansion of semimembranosus)
What are the extra capsular ligaments of knee joint
Medial (tibial) collateral ligament,
Lateral (fibular) collateral ligament
attachments of lateral collateral ligament
Proximally - lateral epicondyle of femur
Distally - depression on lateral fibular head
Attachments of medial collateral ligament
Proximally - medial epicondyle of femur
Distally - medial tibia
Attaches to medial menisci at its midpoint (clinically important)
What reinforces the lateral collateral ligament
Ilio-tibial tract
What is the patellar ligament
Where does it attach
Continuation of quadriceps femoris tendon, distal to patella.
It attaches to tibial tuberosity
What muscles permit knee extension
Quadriceps femoris
Which muscles permit knee flexion
Hamstrings, gracilis, sartorius, popliteus
Which muscles permit lateral rotation of knee (knee must be flexed)
Biceps femoris
Which muscles permit medial rotation of knee (knee must be flexed)
Semimembranosus, Semitendinosus, Gracilis, Sartorius, Popliteus
Benefit of locking knee in extension
Uses less energy to stand
How does the knee lock in extension
Femur rotates internally over tibia
How does the knee unlock
Popliteus helps to rotate femur externally
Why is the lateral menisci injured less than the medial
Smaller and doesn’t have any extra attachments (this makes it less likely to be damaged)
What is torn in an unhappy triad
Medial collateral ligament, medial menisci,
Anterior cruciate ligament
How do you obtain the unhappy triad
Blows to side of extended knee,
Lateral twisting of flexed knee (ACL is taut during flexion)
How can ACL be torn
Hyperextension of knee joint,
Large force to back of knee with the joint partly flexed
Test for ACL damage
Anterior draw test -
Attempt to pull the tibia forwards, positive test if it moves
How can PCL be torn
- ‘Dashboard injury’ - large force applied to shins when knee is flexed.
This pushes tibia posteriorly - Hyperextension of knee joint
- Damage to upper tibial tuberosity
Test for PCL damage
Posterior draw test -
Hold knee in flexed position and attempt to push shin posteriorly, positive test if it moves
Why do peripheral menisci tears usually heal easily
Reasonable blood supply
Articulating surfaces of knee joint
Tibiofemoral - medial and lateral condyles of femur with tibia
Patellofemoral - anterior and distal part of femur with patella
Describe patella dislocation
Patella displaced out of patellofemoral groove.
Mostly occurs laterally
How do patella dislocations occur
Direct trauma on patella,
Forceful sudden twisting of knee
How are patella fractures obtained
Direct trauma to patella,
Sudden contraction of quadriceps femoris
Consequence if patella fractures into fragments
Fragments usually separate:
Proximal fragment - displaced superiorly by quadriceps femoris tendon
Distal fragment - displaced inferiorly by patellar ligament
Important bursae in knee
Supra-patellar,
Pre-patellar,
Superficial infrapatellar
Location of supra patellar bursa
Extension of synovial cavity of knee.
Found between quadriceps femoris and femur
Location of pre patellar bursa
Between apex of patella and skin
Location of superficial infrapatellar bursa
Between patella ligament and skin
What is Housemaids knee and how is it caused
Inflammation of pre patellar bursa which produces swelling on anterior side of knee.
Caused by chronic friction/direct trauma between skin and patella
What is clergyman’s knee and how is it caused
Inflammation of superficial infrapatellar bursa
Caused by chronic friction/direct trauma between skin and tibia
Arthritis in knee
Osteoarthritis is common as knee is weight bearing
Rheumatoid occurs in severe progression of disease
How do you investigate the knee
MRI,
Arthroscopy (camera into joint)
Aspiration (removal of fluid from joint)
Clinical examination
