Anterior surface anatomy

Anterior thigh muscles

Posterior surface anatomy

Posterior thigh muscles

• Dedicated knee coil
• Don’t angle for ACL
• Routine protocol and then assess

• Sagittal PD (TE<30) and fat sat PD (TE36) FOV14, slice 3mm
  • ACL, PCL, menisci, cartilage Coronal T1 and fast STIR (or fat sat PD)
• Coronal T1 and Fast STIR (or fat sat PD) FOV14
  • LCLC, MCL, menisci, cartilage
• Axial STIR FOV14
  • Confirm, support especially ACL, MCL and posterolateral corner pathology
  • Patellofemoral joint
• Review areas
• Common pathology

• Menisci
• Bone
• Cartilage: each compartment
• Ligaments: ACL, PCL, Collateral ligaments, capsule
• Extensor mechanism

Miscellaneous:

• Loose bodies
• Synovium/plicas
• Masses and cysts

• Bow ties: at least two
• Morphology
  • Blunted apex – Surgery
  • Discoid
  • Bucket handle tear
  • Flipped meniscus
  • Cyst

Meniscus Vascular Anatomy

• Signal change – Meniscus windows
  • Grade 1-3
  • 2=enclosed tear
  • 3=tear
  • Sag > Cor to pick up tears
• Pitfalls
• • Transverse meniscus ligament
  • Popliteal tendon
  • Ligament of Humphrey

• Type 3 change
• Abnormal morphology
• Fluid signal intensity on all sequences

Bone

• Bone bruise
• Subchondral infraction
• OCD
• SONK
• Subchondral cysts

Cartilage

• Femorotibial compartments
• Look for subchondral bone changes
• Look for subchondral bone changes

• Spectrum of injuries
  • Bone bruise
  • Osteochondral fracture
  • Osteochondritis dissecans
• Stable, unstable in-situ, loose
• Instability
  • High SI beneath fragment
  • Subchondral cyst
  • Cartilage fracture
  • Displaced fragment

• • • Sprain: clinical grading
    • Partial vs full-thickness tears
    • Tell tale bone contusions to reflect the mechanism of injury
    • Healing/repair can be followed
    • Ganglion formation
    • Some joints: see ligaments better with intra-articular contrast (wrist, elbow, shoulder)

Football/skiing

• External rotation/abduction/hyperextension
• Direct anterior tibia displacement
• Internal rotation, tibia hyperextension (isolated)
• Valgus or varus stresses
• Valgus in extension rotation (MC)
• Deceleration pivot and internal rotation femur

Complete

• Proximal segment
• ⇧ SI
• Angled/wavy fragments
• Cloud, oedema/blood
• Complete absence

Accuracy

• > 90%

• Bone contusions
  • Post lat tibia and lat fem condyle
  • Post med tibia
• Segond fracture
• Anterior drawer
• Uncovered meniscus
• Buckled PCL
• Absent ACL, coronal
• Fluid in the notch on axial
• Meniscus tear (70%) especially LM
• Ligament (MCL 30 %) or capsule tears (post-lat)

Bone Bruise

• Microfracture with haemorrhage in the subchondral bone
• Second “pop” felt at time of injury
  Persists for 6-12 weeks
• Pain proportional to size of bone bruise
• Geographic better prognosis than focal
• Major prognostic indicator- treat as fracture and don’t weight bear
• Career ending injury- osteoarthritis (die is cast)

• Patellar tendon
• More recently hamstring
• Notch width and osteophytes
• Arthrofibrosis/cyclops lesion
• Graft impingement
• Re-rupture

• Arthrofibrosis post ACL reconstruction
• May limit extension and cause locking
• Easily surgically removed

• PCL discontinuity
• Focal or diffuse SI, size
• Anterolateral fem/tib contusions
• Tibial avulsion fx
• MRI > 90% accurate
• Associated MCL, ACL tears common

• Major stresses: athletic, MVA
• Knee: hyperextension, hyperflexion
• Post tibial displacement, knee flexed (dashboard injury)

MCL

• Valgus stress to flexed knee
• Clinical grading system: MRI findings
• Partial, complete MCL tears
  • Peripheral medial meniscus tear
  • Meniscocapsular separation

LCL ligament

Popliteus

• Valgus stress to flexed knee
• Clinical grading system: MRI findings
• Partial, complete MCL tears
  • Peripheral medial meniscus tear
  • Meniscocapsular separation

• Patellar tendon
  • Sag and ax-uniform thickness and black
  • Tendinosis often asymptomatic
• Hoffa’s fat
  • Fat pad impingement
  • Old surgery fibrosis
• Patellar cartilage
  • Chondromalacia
  • softening, fissuring and defects

Intact extensor mechanism allow knee range of motion

• Tenosynovitis peritendinitis
• Tendinosis
• Partial thickness tear
• Full thickness tear
• Complete tear ± retraction

• Common cause of haemarthrosis
• Present after relocation
• Associated with osteochondral fractures
• Bone contusion present: lateral femoral condyle & medial patellar
• Partial/complete tears of the medial retinaculum

• Loose bodies
  • Axials & sag
  • Suprapatella pouch, ant recess and popliteal cyst
• Tendinosis
  • PVNS, erosions
• Masses and cysts
  • Popliteal cyst
  • Bursitis
  • Ganglion