The knee series is a set of radiographs taken to investigate knee joint pathology, often in the context of trauma. It usually comprises an AP and lateral projection, although other non-standard, modified projections can be used for specific indications.

See also knee radiograph (an approach).

Indications

Knee radiographs are indicated for a variety of settings including ^1,2:

• trauma

• bony tenderness at the head of the fibula

• isolated patella tenderness

• patient unable to flex the knee to 90 degrees

• if the patient is unable to bear weight

• suspected osteoarthritis

• detecting joint effusions

• infection

Projections

Standard projections

• AP view

  • demonstrates the distal femur, proximal tibia/fibula and the patella in the AP position

  • ideal projection to assess the tibial plateau and tibiofemoral alignment  

• horizontal beam lateral view

  • orthogonal projection to the AP, routinely done in trauma horizontal beam to better demonstrate any joint effusions

  • ideal projection to assess lipohemarthrosis

  • used to examine the location of the patella and the patency of the patella tendon

Additional projections

• rolled lateral view

  • often performed on bed-bound patients with suspected arthritis

  • orthogonal view of the AP projection

  • demonstrate the joint space, yet sacrifices any assessment of fluid levels

• skyline (Merchant view)

  • superior-inferior projection of the patella; this is an ideal projection for patients that are better suited in the supine position

• skyline (Laurine view)

  • inferior-superior projection of the patella; this projection is best suited to patients able to maintain a semi-recumbent position on the examination table

• knee AP weight-bearing view

  • often used in the context of orthopedic appointments to obtain images of the knees in their natural anatomical position

• knee intercondylar view

  • view utilized to demonstrate intercondylar space, often used for OA and suspected tibial plateau fractures 

• Rosenberg's view

  • weight-bearing projection used to assess joint space-related pathology such as osteoarthritis 

• oblique view

  • two views (internal and external) better demonstrating the knee joint in the absence of CT