Knee Comp Flashcards
What are the prominences on the intercondylar eminence called?
Intercondylar tubercles
How do the tibial plateaus slope?
Slope posteriorly 10-20 deg, 5 deg slope from anterior to posterior margin
What attaches to the tibial tuberosity?
Patellar tendon
How does the fibula sit in relation to the tibia?
Lateral and posterior
What does the fibular head articulate with?
Lateral posteroinferior aspect of lateral condyle
Parts of the fibular head?
Apex, head, neck
What is the largest sesamoid bone?
Patella
Where is patella in relation to knee joint?
Most distal portion (apex) is 1/2” superior to knee joint
Another name for the intercondylar sulcus?
Patellar surface, trochlear groove
Which condyle is more distal?
Medial
What is the surface above the intercondylar fossa (notch)?
Popliteal surface
What attaches to the adductor tubercle? Where?
Tendon of adductor muscle attaches to posterolateral aspect
Which epicondyle is more prominent?
Medial
What attaches to the epicondyles?
Collateral ligaments
What is the patella embedded in?
The tendon of the quadriceps femoris muscle
Flexion vs. Patellar position
45 degrees: patella pulled part way down
90 degrees: patella pulled all the way down
What pass over popliteal surface?
Popliteal blood vessels and nerves
Parts of the patella?
Base (top), apex (bottom), anterior (convex, rough) and posterior surfaces (smooth)
Purpose of the patella?
- Protects the anterior aspect of the knee joint
- Acts as a pivot to increase the leverage of the quadriceps femoris muscle
What does the patella articulate with?
The femur
Major knee ligaments?
- Lateral (fibular) collateral ligament (LCL) : femur to lateral proximal fibula
- Medial (tibial) collateral ligament (MCL): femur to tibia
- Posterior cruciate ligament (PCL): within knee joint capsule
- Anterior cruciate ligaments (ACL): within knee joint capsule
What are collateral ligaments for?
Strong bands at sides, prevent adduction and abduction
What are cruciate ligaments for?
Strong, rounded cords that cross and attach to anterior/posterior aspects of the intercondylar eminence of tibia, prevent anterior/posterior movement
Where is the infrapatellar fat pad located?
Posterior to the patellar ligament, aids in protection of the knee joint
Parts of the bursa of the knee joint?
- Suprapatellar bursa
- Infrapatellar bursa
-separated by the infrapatellar fat pad
Menisci of the knee?
Medial and lateral
Fibrocartilgenous discs between the tibial plateaus and femoral condyles
Crescent shaped
Thicker at external margins, thin in middle
Shock absorbers
Produce synovial fluid along with synovial membrane
What are the articulating ends of the femur and tibia covered in?
Hyaline membrane
Frequent knee trauma?
Torn ACL and MCL associated with tear of medial meniscus
-MRI or arthrography used to visualize
What classification is the femorotibial joint?
- Bicondylar
- flexion/extension/some gliding and rotation when knee is partially flexed
What classification is the patellofemoral joint?
- sellar/saddle
- considered saddle because of shape and relationship of patella to anterior distal femur
Joints that make up the knee joint?
Femorotibial joint
Patellofemoral joint
Flexion of the knee vs patellar position on an AP knee?
20 degrees: patella on patellar surface
30-70 degrees: patella is demonstrated between the patellar surface and IC fossa
90 degrees: patella within the IC fossa
Where is the patella located when it is subluxed?
More lateral than normal
On an AP knee, how does flexion relate to the amount of IC fossa demonstrated?
More flexed = more IC fossa
When is the IC fossa in profile?
Femur at 60-70 degrees to table, 20-30 degrees with CR
How do you align the CR with a non-extendible knee?
Align CR perpendicular to lower leg, then decrease the angle 5 degrees
(Increased foreshortening with increased angle)
2 types of joint space narrowing?
Valgus: lateral compartment narrower than medial
Varus: medial compartment narrower than lateral
AP knee: if fibular head is foreshortened and demonstrated more than 1/2” distal to tibial plateau, what is wrong with the angle?
Cephalic angle too great
Fat pads of the knee
-Anterior suprapatellar fat pad
-Posterior suprapatellar fat pad
Both anterior to patellar surface of femur
What indicates joint effusion on a knee?
Separation of the anterior and posterior suprapetallar fat pads
When will an AP knee be magnified?
- if a curved detector is not used
- if OID is present
What is the air gap technique?
Increased OID = decreased scatter caught by the IR (no grid needed) = increased contrast
Technique for knee?
60-70 kVp
How to demonstrate a subluxed patella?
Quadriceps femoris must be relaxed, patella could appear normal if not
What happens if the distal femur is lower than the proximal femur when using an axial viewer?
Anterior soft tissue will be projected into the joint space and it will appear open, but underexposed
What is a bone cyst?
A well circumscribed lucency
What is chondromalacia patella?
Pathology of the femoropatellar joint space, possible misalignment of the patella
What is chondrosarcoma?
Bone destruction with calcifications in cartilagenous tumours
What is enchondroma?
Benign cartilagenous tumour, well defines radiolucent with thin cortex, causes pathological fractures
What is Ewing’s sarcoma?
Malignant bone tumour, ill-defined area of bone, onion peel
What is extosis?
Projection of bone with cartilagenous cap, grows parallel to shaft away from joint
What is multiple myeloma?
Cancerous bone tumour, punched out osteolytic lesions
What is osgood schlatters disease?
Detachment of the tibial tuberosity by patellar tendon
What is osteoclastoma?
Radiolucent lesions with thin strips of bone
What is osteogenic sarcoma?
Destructive lesion with periosteal reaction, sunburst pattern
Osteoid osteoma?
Oval density with lucent center
Osteomalacia?
Rickets
Decreased bone density, bowing, softening of bone
Pagets
Dense, soft bone
Reiter?
Erosion of the tibial tuberosity due to achilles tendon pulling
Rosenburg method?
Standing PA, 45 degree flexion of knee
CR angle for lateral knee based on pelvis size and femur length?
Wide pelvis and short femur = increase angle
AP knee CR angulation based on pevis size?
Less than 19cm: 305 deg caudad
19-24cm: 0 deg
Greater than 24 cm: 3-5 deg cephalad
What line is parallel to the IR for an AP knee?
Interepicondylar line
If medial oblique knee is over-rotated, what happens?
Femoral condyles demonstrate superimposition
Lateral oblique: fibula is demonstrated without complete tibial superimposition
The patient knee was rotated less than 45 degrees (under rotated)
Lateral oblique: the fibula is seen with posterior placement on the tibia?
The knee was over-rotated
X-table knee: the lateral condyle is proximal to medial and the fibular head is less than 1/2” from the tibial plateau?
Leg was abducted from body
What is the IC fossa view used to demonstrate?
Loose bodies, split and displaced cartilage is osteochondritis dissecans, and flattening or underdevelopment of the lateral femoral condyle is congenital slipped patella
Patella view: tibial tuberosity is demonstrate in the joint space?
Knee not bent enough
Patella view: medial and lateral condyles demonstrate the same height, patella is lateral?
Leg is not rotated enough to place epicondyles parallel to IR (lateral condyle should be higher)
What is a merchant view?
Patella
40 degrees flexion
CR 30 deg caudad
(Axial viewer?)
Inferosuperior patella
AP
Pt supine, 45 degrees flexion
CR 10-15 degrees from lower leg
Hughston patella
PA
55 deg flexion (greater than 45)
CR 15-20 degrees from lower leg
Settegast method patella
Pt prone
90 degrees flexion
CR 15-20 degrees from lower leg
Hobbs method patella?
Superoinferior
Camp coventry method IC fossa?
Prone
40-50 degrees flexion
Holmblad method IC fossa
Prone
60-70 deg flexion
Beclere method IC fossa
Supine, AP
40-45 deg flexion
What is best demonstrated on a x-table lateral knee?
joint effusion, lipohaemarthrosis, and intra-articular fracture
