9. Knee joint

Question 1

What is the name for the indent where the patella slides in and out of, between the two condyles

Answer 1

Trochlea groove / patella groove

Question 2

Whats the strengths of Lateral view vs Horizontal view

Answer 2

Lateral view is good to asses position of patella and see weight bearing alignment in erect xrays whereas
Horizontal view is good to assess joint effusion and lipohaemarthrosis by exploiting the different physical and XR densities of bodily substances –(not erect)

Question 3

What is the skyline view used for - requires flexing of the knee.

Answer 3

Allows better look at patellofemoral joint for patella fracture/ dislocation or osteoarthritis- narrower joint space

Question 4

How do you tell the femoral condyles apart on a skyline view

Answer 4

Lateral condyle projects more anteriorly than medial

Question 5

What is a hallmark of osteoarthritis

Answer 5

reduction of joint space leading to abnormal alignment when on one side more than other due to cartilage getting worn down

Question 6

Which side does the patella commonly dislocate- causing instability of the knee

Answer 6

lateral due to more vastus muscles with lateral origin

Question 7

What is a lipohaemarthrosis

Answer 7

Fat from medullary cavity and blood from a fracture getting into the joint space. As fat is less dense than blood it is shown as darker on xray as liquid is close to muscle density. It also means it rises to the surface on a horizontal scan. In the knee it goes in the suprapatella bursa

Question 8

In what order are dislocations described in the knee - and in general

Answer 8

The distal fragment is described relative to the proximal fragment.
Therefore tibia position relative to femur

Question 9

What structures are likely to be damaged in a dislocation

Answer 9

Ligaments, menisci, popliteal artery and common peroneal nerve