PA AXIAL WEIGHT-BEARING BILATERAL KNEE PROJECTION: KNEE

Rosenberg Method
Pathology Demonstrated:

• Femorotibial joint spaces of the knees are demonstrated for possible cartilage degeneration or other knee joint pathologies. Demonstrates knee joint spaces, as well as intercondylar fossa. Both knees are included on the same exposure for comparison.

Technical Factors

• IR size - 30 x 35 cm (11 x 14 inches) or 35 x 43 cm (14 x 17 inches), lengthwise
• Moving or stationary grid
• 70 +- 5 kV range
• mAs 6

Shielding: Shield gonadal area.

Patient and Part Position:

Rosenberg Method

• Take radiograph with patient erect, standing on attached step of x-ray table or on step stool if the upright-bucky is used, so that patient is placed high enough for 10 degree caudad angle.
• Position feet straight ahead with weight evently distributed on both feet and knees flexed to 45 degree; have patient use Bucky device for support, with patella touching the upright Bucky.
• Align and center bilateral legs and knees to CR and to midline of upright Bucky and IR; IR height adjusted to CR.

Central Ray:

• CR angled 10 degree caudad and centered to directed to midpoint between knee joints at level 1/2 inch (1.25 cm) below apex of patella when a bilateral study is performed: or CR centered to directed to midpoint of knee joint at level 1/2 inch (1.25 cm) below apex of patella when a unilateral study is performed.
• Minimum SID of 40 inches (100cm)

Collimation:

• Collimation to bilateral knee joint region, including some distal femora and proximal tibia for alignment puposes.

Alternative unilateral projection:

• If requested, this exam may be performed unilaterally with facing the upright Bucky or IR holder, knee flexed to 45 degree, feet straight ahead.
• The patient to balance with minimal pressure placed on the contralateral side. Direct CR to 10 degree caudad (parallel to tibial plateau) level of knee joint for this PA unilateral projection.

Radiographic Criteria:

Structure Shown:

• The distal femur, proximal tibia, and fibula, femorotibial joint spaces, and intercondylar fossa are demonstrated bilaterally or unilaterally.

Position:

• No rotation of both knees is evident in the symmetric appearance of femoral and tibial condyles.
• The  intercondylar fossa should be open

Collimation an CR:

• Knee joint spaces should appear open if CR angle was correct and tibia was flexed 45 degree.
• Collimation field should centered to knee joint spaces.

Exosure Criteria:

• Optimal exposure should visualized the intercondylar fossa and the proximal tibia with an open joint space.
• Trabecular markings of all bones should appear clear and sharp, indicating no motion.