Knee radiograph (an approach)
Knee radiograph (an approach)
Systematic review
Effusion?
Check for an effusion on the lateral:
- peripatellar fat pads should sit next to each other
- soft tissue density between them indicates an effusion
- if simple effusion (hemarthrosis), think severe ligamentous, meniscal or intra-articular bony injury
- if fat-fluid level (lipohemarthrosis), think an intra-articular fracture
Tibiofemoral alignment
- draw a line down the lateral margin of the lateral femoral condyle
- if > 5 mm tibia is observed outside the line, think tibial plateau fracture
Plateau review
- carefully look for a proximal tibial fracture
- pay particular attention to:
- tibial spine: avulsion
- lateral tibial plateau: small avulsion (Segond fracture)
- areas of increased density may point to underlying fracture
- medial epicondyle: don't overcall calcification adjacent to the medial femoral epicondyle (Pellegrini-Stieda lesion)
Patella
- fractures are usually easy to spot
- don't call a bipartite patella a fracture: well-corticated unfused center at the superolateral pole
- check for patella tendon disruption
- patella tendon: inferior pole of patella to tibial tuberosity
- patella tendon length = patella length ± 20%
- if increased, think patella tendon rupture
Common pathology
Lipohemarthrosis
- fat and blood from bone marrow collect in suprapatellar bursa
- a fat-fluid level may be the only sign of intra-articular fracture
- associated with tibial plateau or distal femoral fractures
- more: lipohemarthrosis
Tibial plateau fracture
- 80% involve the lateral plateau
- fall from height or car bumper impact
- associated significant cruciate and medial collateral ligament damage
- more: tibial plateau fracture
Segond fracture
- avulsion fracture; bony fragment adjacent to lateral tibial plateau
- internal rotation and varus stress; falls or sports
- 75% associated with anterior cruciate ligament injury
- more: Segond fracture
Intercondylar eminence fracture
- typically avulsion fracture of tibial attachment of anterior cruciate ligament
- mechanism: rapid deceleration or hyperextension of the knee
- most common in adolescents
- more: intercondylar eminence fracture
Patella fracture
- majority transverse, also vertical or comminuted
- direct blunt force or violent contraction of quadriceps
- oblique or skyline views will confirm fractures
- more: patella fracture
Distal femoral fracture
- 6% of all femur fractures
- bimodal distribution
- high energy blunt trauma; falls in elderly
- more: distal femoral fracture
Proximal fibula fracture
- typically occur with lateral tibial plateau fractures, but may be isolated
- varus force
- associated with lateral collateral ligament damage
- more: proximal fibula fracture
Don't miss...
Pellegrini-Stieda lesion
- post-traumatic soft-tissue calcification adjacent to medial epicondyle of femur
- ossification following injury to medial collateral ligament
- do not misdiagnose as a fracture
- more: Pellegrini-Stieda lesion
Related Radiopaedia articles
Approaches to radiographs
- adult
- head, neck and spine
- skull radiograph
- facial radiographs
- cervical spine radiograph
- thoracolumbar spine radiograph
- upper limb
- chest
- frontal
- lateral
- decubitus
- abdomen
- lower limb
- head, neck and spine
- child
- head, neck and spine
- skull radiograph
- facial radiographs
- cervical spine radiograph
- thoracolumbar spine radiograph
- upper limb
- shoulder radiograph
- elbow radiograph
- wrist radiograph
- hand radiograph
- chest
- abdomen
- lower limb
- pelvic radiograph
- knee radiograph
- ankle radiograph
- foot radiograph
- head, neck and spine
