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4O39 > Knee Anat, Patho & MRI apperance > Flashcards

Knee Anat, Patho & MRI apperance Flashcards

(52 cards)

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1
Q

What type of joint is the knee and what two joints does it consist of?

A

The knee is a compound synovial joint consisting of:

  • Tibiofemoral joint
  • Patellofemoral joint
    It serves as a hinge joint allowing flexion and extension movements.
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2
Q

What are the range of motion capabilities of the knee joint?

A
  • Flexion and extension (primary movements)
  • Internal rotation (~10 degrees)
  • External rotation (~30-40 degrees)
  • Valgus and varus movements
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3
Q

What are the 3 bones that form the knee joint and their articulations?

A

Bones:
- Femur
- Tibia (fibula is NOT part of knee joint)
Patella (largest sesamoid bone)

Articulations:

-Tibiofemoral: medial and lateral femoral condyles articulate with tibial condyles
-Patellofemoral: patella articulates with anterior aspect of distal femur

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4
Q

What is articular cartilage made of and what is its function?

A

Made of chondrocytes which produce extracellular matrix containing:

  • Collagen fibres
  • Proteoglycan
  • Elastin fibres

Function: Covers articular surfaces and allows bones to freely glide across one another.

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5
Q

What is the gold standard MRI technique for imaging cartilage and what are the advanced techniques mentioned?

A

-Gold standard: T2 sequence MRI

Advanced techniques:
- QDESS (Quantitative Double Echo Steady-State)
- T2 mapping
- Quantification of cartilage changes at different points

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6
Q

What is QDESS and how does it work?

A

QDESS (Quantitative Double Echo Steady-State) is a pulse sequence that generates 2 distinct echo times with different contrast properties from a single acquisition:

  • First echo (S+): More T1/PD-weighted (captures signal before refocusing pulse)
  • Second echo (S-): More T2-weighted (captures signal after refocusing pulse)
    Combined data allows quantitative mapping of T2 relaxation times, correlating with cartilage water content and collagen fiber integrity
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7
Q

Define T1 and T2 relaxation and their characteristics

A
  • T1 relaxation (longitudinal): Time for protons to realign with main magnetic field
  • T2 relaxation (transverse): Time for protons to dephase/lose synchronization
  • Water: long T1 and T2
  • Fat: short T1 and medium T2
  • Solid tissues: short T1 and T2
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8
Q

What are the characteristics of T1-weighted vs T2-weighted images?

A

T1-Weighted:

  • Shows anatomy clearly
  • Fat appears bright (white)
  • Water/fluid appears dark
  • Good for brain structure, fatty tissues, contrast enhancement

T2-Weighted:

  • Shows pathology clearly
  • Water/fluid appears bright (white)
  • Fat appears grey
  • Good for detecting edema, inflammation, pathological processes
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9
Q

What are TE and TR parameters and their values for different weightings?

A

TE (Time to Echo)

= Time between initial RF pulse and signal measurement
- Short TE (<30ms): T1-weighted
- Long TE (>80ms): T2-weighted

TR (Time to Repetition)

= Time between successive pulse sequences
- Short TR (<1000ms): T1-weighted
- Long TR (>2000ms): T2-weighted

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10
Q

What is FLAIR and when is it used?

A

FLAIR (Fluid Attenuated Inversion Recovery):

  • Special T2-weighted image that suppresses cerebrospinal fluid signal
  • Makes lesions near fluid-filled spaces more visible
  • Particularly useful for brain imaging
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11
Q

What are the 4 main muscle groups around the knee and their functions?

A
  1. Quadriceps: 4 parts connecting into quadriceps tendon (extension)
  2. Hamstrings: 3 parts (flexion)
  3. Popliteus: allows slight rotation
  4. Gastrocnemius: connects femur to calcaneus posteriorly
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12
Q

Name the 4 components of the quadriceps muscle.

A
  • Vastus lateralis
  • Vastus medialis
  • Vastus intermedius
  • Rectus femoris
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13
Q

Name the 3 components of the hamstring muscles and their attachments.

A
  • Biceps femoris: connects to fibula
  • Semimembranosus: connects to medial tibia
  • Semitendinosus: connects to medial tibia
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14
Q

Describe the popliteus and gastrocnemius muscles.

A

Popliteus: Connects lateral femur to medial tibia

Gastrocnemius: Connects femur to calcaneus posteriorly

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15
Q

What are the main ligament groups in the knee?

A
  • Cruciate ligaments (ACL and PCL)
  • Collateral ligaments (MCL and LCL)
  • Patellar ligament
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16
Q

Describe the anatomy and function of the ACL

A

Anatomy: Runs from intercondylar fossa of femur to anterior intercondylar area of tibia

Primary function: Limit anterior movement of tibia relative to femur

Secondary functions: Prevent hyperextension, limit rotation and valgus forces

Bundles: Anteromedial and posterolateral bundles

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17
Q

Describe the anatomy and function of the PCL

A

Anatomy: Runs from anteromedial intercondylar area of tibia to femur

Subdivisions: Anterolateral (65%) and posteromedial (35%)

Primary function: Limit posterior movement of tibia relative to femur

Secondary functions: Prevent hyperflexion, limit internal valgus and varus rotations

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18
Q

What is the patellar ligament and its alternative name?

A
  • Continuation of quadriceps femoris tendon attaching distal patella to tibial tuberosity
  • Also called “patellar tendon” as it technically extends from quadriceps muscle to patella
  • Tendons connect muscles to bone
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19
Q

What are the meniscofemoral ligaments and their names?

A

Connect posterior horn of lateral meniscus to lateral aspect of medial femoral condyle:

  • Anterior: Ligament of Humphrey
  • Posterior: Ligament of Wrisberg
    They become 2 distinct bands at the PCL
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20
Q

Compare the medial and lateral menisci characteristics.

A

Medial Meniscus:

  • Open C shape
  • Posterior horn larger than anterior
  • Covers 50% articular surface
  • Less mobile due to tight meniscocapsular junction

Lateral Meniscus:

  • Tight symmetrical C shape
  • Covers 70% articular surface
  • More mobile due to looser capsular attachments
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21
Q

What are the functions of the menisci?

Study These Flashcards
A
  • Absorb acute shocks
  • Contribute to joint stability
  • Act like a wedge
  • Secondary stabilizer in ACL deficiency
  • Aid in distribution of synovial fluid
  • Take up to 55% of total load when standing
22
Q

How do menisci appear on MRI and what attachments do they have?

Study These Flashcards
A

MRI Appearance: Normally hypointense (black) structures

Attachments: Strong central tibial attachments called root ligaments

Assessment: Use axial to identify, then confirm injuries on coronal and sagittal planes

23
Q

Describe the three main MRI planning orientations for knee imaging

Study These Flashcards
A

Axial Planning:
- Parallel to tibial plateau
- Include patellar ligament insertion inferiorly and patella superiorly

Coronal Planning:
- Parallel to posterior femoral condylar line
- Include patella and slices posterior to condyles to include popliteal artery

Sagittal Oblique Planning:
- Parallel to lateral condyle (results in slices parallel to ACL)
- Include all of both condyles

24
Q

What is the recommended sequence for reviewing knee MRI?

Study These Flashcards
A

Review in order: Coronal → Sagittal → Axial (opposite to acquisition order)

25
How do different structures appear on MRI sequences?
Normal Structures: - Tendons, ligaments, menisci: Dark (hypointense) on all sequences - Fat: Bright on all sequences - Fluid: Dark on T1-W, bright on T2-W Pathological: - Damaged structures appear bright (especially on T2-W) - Bone marrow edema: Bright signal on PD or PD FS
26
What is the "Magic Angle" effect and how is it avoided?
- Artifact making normal tendons appear abnormally bright when running at ~55° to main magnetic field - Prevention: Use TE of 37ms or above in PD-W sequences -Helps reduce false positives
27
What should be assessed on coronal knee MRI images?
- Bones and marrow signal: Osteophytes, joint space, patella cortical bone - Bone marrow edema: Bright signal on PD or PD FS - Fluid signal: Normal/abnormal patterns and quantities - Ligaments and menisci: Check for black appearance and bright fluid around/within - Cartilage: Well-delineated against fluid and bone on PD FS
28
What is MR arthrography and what is the protocol?
Definition: Procedure enhancing internal joint visualization by injecting contrast into joint space Protocol: 1. Inject 10-20ml contrast (dilute gadolinium, 1:100) under fluoroscopic guidance 2. Minimize knee movement 3. Scan within 15-20 minutes 4. All sequences are T1-W FS Use: Helpful in meniscus retear cases
29
List the common acute knee pathologies
- Dislocation - Fracture - ACL tear - PCL tear - Collateral ligament tears - Meniscal tears - Tendon tears (quadriceps and patellar)
30
What are the 5 types of femoral-tibial dislocation?
1. Anterior: Forced hyperextension (MVAs, sporting collisions) 2. Posterior: Direct force on flexed knee (dashboard injury) 3. Medial: Valgus/varus forces 4. Lateral: Lateral displacement 5. Rotary: Rotary force
31
What is the most common mechanism for patellar dislocation?
Most common in active young adults in sport Knee flexion and valgus stress (over 90% of cases)
32
What are the specific fracture types mentioned and their mechanisms?
- ACL avulsion: Severe hyperextension - PCL avulsion: Dashboard injury or severe hyperextension - Segond fracture: Cortical avulsion of tibial attachment of anterolateral ligament/IT band - Arcuate complex avulsion: Avulsion at fibular head level - Patellar: Chondral/osteochondral lesions following dislocation
33
What are the mechanisms of ACL injury and their frequencies?
Non-contact (70-80%): - Running and cutting to same side - Pivoting - Landing - Hyperextension Contact (associated with meniscus/ligament injuries): - Clipping injury - Hyperflexion - Hyperextension
34
What are the direct and indirect signs of ACL tear on MRI?
Direct Signs: - Loss of ligament continuity Indirect Signs: - Buckled PCL - Abnormal PCL line - Abnormal femoral line Ancillary Findings: - Bone bruising pattern - Other bony injuries
35
What characterizes partial ACL tears?
- Anteromedial bundle more commonly torn Difficult MRI diagnosis in acute phase due to hematoma Best seen on fluid-sensitive axial images
36
What meniscal tears are associated with ACL injury?
- Popliteomeniscal fascicles - Corner tears, Wrisberg Rip - Vertical longitudinal tears
37
Describe PCL anatomy and injury characteristics.
Anatomy: - Arises from posterior tibial shelf - Broad femoral fan-like insertion to lateral surface of medial femoral condyle - 12 to 7:30 orientation Injury Characteristics: - Less commonly injured than ACL - Twice as strong as ACL - Often partial tears from trauma - Potential to scar and reconstitute (may appear lax/wavy on MRI)
38
What are the mechanisms of PCL injury?
- Anterior force to flexed knee (dashboard injury) - Hyperflexion injury - Hyperextension injury - Distraction
39
How are PCL injuries graded?
- Grade I to III where Grade III is non-functioning ligament - MRI highly accurate in diagnosing acute tears
40
Describe MCL anatomy and injury grading.
Anatomy: Broad, flat ligament attached to medial condyle, adheres to medial meniscus, inserts posteriorly into medial tibial condyle Mechanism: Direct blow to outside of knee (valgus stress) Grading: - Grade 1: Minor sprain, high signal medial to normal-appearing ligament - Grade 2: Severe sprain/partial tear, high signal medial to ligament with partial disruption - Grade 3: Complete ligament disruption
41
Describe LCL anatomy and injury mechanism
Anatomy: - Rounded and much smaller than MCL - NOT fused to lateral meniscus or capsular ligament Mechanism: Blow to medial side (varus stress) or hyperextension
42
Describe the different types of meniscal tears
Radial Tear/Root Tear: - Absent/empty meniscus sign on sagittal images adjacent to PCL - Confirmed on coronal images Longitudinal Tears: - Parallel to meniscus long axis - Never reaches inner margin Parrot Beak Tear: - Complex displaced radial/oblique tear - Curved crescent appearance on axial images - Curved V-shaped tear gap
43
What is a bucket handle tear and its MRI signs?
Definition: Meniscal tear with fragment in intercondylar notch MRI Signs: - Double PCL sign (fragment flips centrally, appears anteroinferior to PCL) - Double delta sign (inner fragment flipped anteriorly) - More common in medial than lateral meniscus
44
What is O'Donoghue (unhappy/terrible) triad?
45
Describe patellar tendon tears and associated conditions
Characteristics: - Usually traumatic - Complete or partial Most common at proximal tendon/inferior pole junction Associated Conditions: Diabetes mellitus Chronic renal failure Rheumatoid arthritis
46
Describe quadriceps tendon tears and risk factors
Mechanism: Direct blow or forced knee flexion Type: Complete or partial Risk Factors: - Connective tissue disorders (SLE, RA) - Corticosteroid use - Renal impairment - Spontaneous rupture uncommon
47
What is patellar tendinopathy (Jumper's knee)?
48
Describe meniscal degeneration characteristics
- Significant role in knee pain with aging - Macroscopic and microscopic degeneration - Result from repetitive wear and tear - Similar tear patterns to acute scenarios but more complex - Usually involve posterior horns and mid-body
49
What is bursitis and its cause?
- Bursae irritation from repetitive trauma - Increased synovial fluid production - Swelling causes pain and limited movement
50
Describe osteoarthritis in the knee.
- Most common form of arthritis (then RA) - Joint cartilage degeneration from wear and tear - End result may be bone-on-bone contact
51
What are isotropic voxels and their advantage?
Definition: Voxels with same dimensions on X, Y, Z planes Advantage: Allows reconstructions for all 3 planes with equal resolution
52
What is the significance of high-resolution sequences for ACL imaging?
- Needed to see fine details like anteromedial/posterolateral ACL bundles - Without high resolution, can only see one hypointense structure instead of separate bundles -Critical for accurate ACL assessment

4O39 (6 decks)

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