Updated: 9/17/2018

Adult Knee Trauma Radiographic Evaluation

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NORMAL ANATOMY
 Osteology
  • Distal femur
    • anterior/posterior view
    • lateral view 
  • Proximal tibia
    • anterior/posterior view 
  • Patella
    • anterior/posterior view 
 Attachments
  • Muscle
    • anterior view 
    • posterior view 
    • lateral view 
  • Ligament/tendon
    • anterior/posterior view
    • lateral view
RADIOGRAPHIC VIEWS
 AP/PA view
  • Positioning
    • patient
      • supine (AP) vs. prone (PA) 
      • knee extended + leg IR 3-5°
    • beam
      • aim 1.5cm distal to apex of patella
  • Indications
    • fracture
    • joint alignment
    • OA
      • PA view preferred over AP view
      • weightbearing view preferred over non-weightbearing view
  • Critique 
    • symmetrical femoral + tibial condyles
    • fibular head should be bisected by the tibia
    • visualization of intercondylar eminence in intercondylar fossa
 Lateral view
  • Positioning
    • patient
      • rolled lateral (mediolateral) = lateral decubitus on ipsilateral side + knee flexed 20-30°
      • horizontal ray (lateromedial) = supine + knee extended
    • beam
      • aim 2.5cm distal to medial epicondyle
      • tilt 5-7° cephalad (if rolled lateral)
  • Indications
    • patella fracture = horizontal ray view to avoid displacement
    • patella alta/baja = requires knee in 30° flexion
    • trochlear dysplasia
    • OA
    • joint effusion
  • Critique 
    • visualization of suprapatellar fat pad = via knee flexion < 30°
    • appropriate IR/ER
      • superimposition of posterior aspect of femoral condyles
      • superimposition of fibular head + tibia
      • open patellofemoral joint
      • no visualization of adductor tubercle
    • appropriate cephalad angulation = open tibiofemoral joint
  Oblique view 
  • Positioning
    • patient
      • AP = supine + knee extended + leg IR/ER 45°
      • PA = prone + knee flexed 10° + leg IR/ER 45°
    • beam
      • aim 1.5cm distal to apex of patella
  • Indications
    • fracture = femoral condyle, patella
    • OA
    • intercondylar fossa pathology = loose bodies
  • Critique 
    • superimposition of patella + ipsilateral femoral condyle
    • asymmetrical tibiofemoral joint spaces
 Tangential view
  • Positioning 
METHOD
PATIENT
BEAM
Sunrise/Settegast supine vs. prone knee flexed 90° inf-sup
10-20° cephalad
Hughston
prone knee flexed 50-60° inf-sup 45° cephalad
Merchant supine knee flexed 40° sup-inf 30° caudad
Laurine
semi-recumbent knee flexed 30° inf-sup 30° cephalad
  • Indications
    • patellar malalignment
    • trochlear groove depth
    • OA
    • vertical patella fracture
  • Critique 
    • visualization of femoral condyles + trochlear groove
    • no superimposition of patella + femur
    • open patellofemoral joint
 Intercondylar view 
  • Positioning
METHOD
PATIENT
BEAM
Beclere supine knee flexed 40° AP 40° cephalad
Camp Coventry/Tunnel
prone knee flexed 40° PA 40° caudad
Holmblad erect vs. kneeling knee flexed 70° PA
  • Indications
    • OCD = displaced cartilage
    • congenital slipped patella = flattening/underdevelopment of lateral femoral condyle
    • hemophilia = intercondylar widening
    • intercondylar fossa pathology = loose bodies
  • Critique 
    • superimposition of patella + ipsilateral femoral condyle
    • asymmetrical tibiofemoral joint spaces
NORMAL FINDINGS
  • Normal anatomy anatomy chart
  • Normal variants
    • fabella
      • sesamoid bone in lateral head of gastrocnemius
      • best seen on lateral view
    • cyamella
      • sesamoid bone in popliteus tendon
      • usually present in lateral aspect of distal femur in popliteal groove
      • best seen on AP view
    • cortical desmoid
      • cortical lucency in posteromedial aspect of distal femur
      • represents origin of medial head of gastrocnemius + insertion of adductor magnus
      • seen in adolescents (10-15 yo)
    • bipartite/tripartite patella
      • usually superolateral with smooth margins
    • double-layered patella
      • rare form of bipartite patella
      • multiple fragmented patella with smooth well-corticated borders
      • pathognomonic for multiple epiphyseal dysplasia
CLINICAL PEARLS
 Ottawa knee rules
  • XRs are indicated if any of the following criteria are met 
    • > 55yo
    • TTP of fibular head
    • isolated TTP of patella
    • inability to flex knee 90°
    • inability to bear weight, i.e. ambulate >4 steps
 Knee effusion
  • Fluid density in suprapatellar pouch + around Hoffa’s triangle (anterior femoral condyles) 
    • can estimate volume of effusion from width of suprapatellar pouch 
  • Anterior displacement of patella
  • Lipohemarthrosis 
  • Bowing vs. blurring of posterior aspect of quads tendon
  • Joint space widening
  • Bulging of posterior fat lines
  • Displacement of fabella
 Distal femur fracture  
  • Recommended views
    • AP
    • lateral
  • Optional views
    • traction views
      • AP, lateral, and oblique traction views can help characterize injury but are painful for patient
    • adjacent joints
      • always obtain views of joint above and below
    • conralateral femur
      • consider views of contralateral femur for pre-operative planning and templating
  • Findings
    • Hoffa fracture
      • intra-articular supracondylar distal femoral fracture in the coronal plane
      • may be seen on lateral view
    • in elderly patients, evaluate for any pre-existing knee DJD
  • Treatment criteria
    • nonoperative treatment rarely indicated but can attempt if:
      • non-displaced
      • non-ambulatory
      • multiple medical co-morbidities
    • retrograde IM nail if
      • supracondylar fracure
      • osteoporotic bone
    • ORIF if
      • intra-articular
      • displaced
      • nonunion
    • distal femoral replacement if
      • unreconstructable fracture
      • fracture around prior total knee arthroplasty with loose component
 Patella fracture  
  • Recommended views
    • AP
    • lateral
      • best view to see transverse fx
    • tangential
      • best view to see vertical fx
  • Findings
    • fracture displacement
      • degree of fracture displacement correlates with degree of retinacular disruption
    • patella alta
  • Treatment criteria
    • nonoperative treatment acceptable if
      • intact extensor mechanism = able to perform straight leg raise
      • non-displaced/minimally displaced
      • vertical fracture
    • ORIF if
      • failed extensor mechanism
      • open fracture
      • articular step-off > 2mm
      • displacement > 3mm
    • partial patellectomy if comminuted superior or inferior pole fracture measuring <50% patellar height only if ORIF is not possible
    • total patellectomy if severe and extensive comminution not amenable to salvage
 Tibial plateau fracture  
  • Recommended views
    • AP
    • lateral
    • oblique
      • oblique is helpful to determine amount of depression
  • Optional views
    • plateau view
      • 10 degree caudal tilt
  • Findings 
    • on AP view
      • depressed articular surface
      • sclerotic band of bone indicating compression fx
      • abnormal joint alignment
    • on lateral view
      • posteromedial fracture lines must be recognized 
  • Treatment criteria
    • nonoperative treatment acceptable if
      • minimally displaced split or depressed fractures
      • low energy fracture stable to varus/valgus alignment
      • nonambulatory patients
    • ex-fix (temporizing or definitive) if
      • significant soft tissue injury
      • polytrauma
      • highly comminuted fractures where internal fixation not possible
    • ORIF if
      • articular step-off > 3mm
      • condylar widening > 5mm
      • varus/valgus instability
      • involvement of medial plateau
      • bicondylar
 Proximal tibia fracture  
  • Recommended views
    • AP
    • lateral
    • ipsilateral knee, tibia, and ankle
  • Findings
    • proximal fragment extended, apex anterior, varus
      • extended and apex anterior due to patellar tendon
      • varus due to pes anserinus + anterior compartment
    • distal fragment flexed
      • flexed due to hamstrings
  • Treatment criteria
    • nonoperative treatment acceptable if
      • < 1cm shortening
      • < 5° varus-valgus angulation
      • < 10° AP angulation
      • < 10° rotational deformity
      • > 50% cortical apposition
    • IM nail if enough proximal bone to accept two locking screws (5-6 cm)
    • percutaneous locking plate if inadequate proximal fixation for IM nailing
 

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