AP Weight-Bearing Knees

• Bilateral femoral condyles under weight-bearing stress.
• Bilateral tibial plateaus with joint space narrowing.
• Bilateral patellas centered and symmetric.
• Femorotibial joint spaces bilaterally.
• Alignment of mechanical axis bilaterally.
• Overall lower extremity alignment under full weight load.

• Verify patient identity using two identifiers.
• Remove shoes and any radiopaque items from both legs.
• Have patient stand upright on both feet on a low platform.
• Position feet slightly apart with weight equally distributed.
• Keep knees fully extended in neutral position.

Center point between both knees at 1 inch below patella apexes.

Perpendicular to center of both knees in standing.

kVp

60–75

mAs

5–10

SID

40" (102 cm)

Notes

Weight-bearing view shows joint space narrowing and alignment under load.

• Both knee joint spaces visible and symmetric.
• Femoral condyles and tibial plateaus symmetric bilaterally.
• Patellas centered and symmetric in both knees.
• No rotation; both knees in true AP alignment.
• Full extent of both femurs, knees, and proximal tibias included.
• Collimation 1 inch on sides, 1.5 inches above and below knees.

1. 1 Unequal weight distribution rotates one knee laterally or medially.
2. 2 Patient leaning distorts symmetry between bilateral knees.
3. 3 Knee flexion closes joint spaces and obscures cartilage.
4. 4 Off-centered CR omits one knee or both knees incompletely.

• Degenerative joint disease severity assessment under weight-bearing stress.
• Varus or valgus alignment evaluation with weight on both legs.
• Joint space narrowing or cartilage loss assessment.
• Post-operative alignment verification under full weight-bearing.