Measuring knee alignment involves assessing the mechanical axis of the leg, providing insights into potential issues like bowlegs (varus) or knock-knees (valgus). A standard method involves drawing a specific line on an A/P X-ray.
Assessing Knee Alignment: The Mechanical Axis
The measurement is done by analyzing the mechanical axis of the leg on an anterior-posterior (A/P) X-ray.
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The Line: The key is to draw a line that represents the mechanical axis of the lower limb.
- The line starts at the center of the femoral head (hip joint).
- It passes through the center of the knee joint.
- It continues down to the center of the ankle joint.
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Ideal Alignment: In a perfectly aligned leg, this line will pass directly through the center of the knee.
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Varus (Bowlegs): If the line passes medial (inside) to the center of the knee, this indicates a varus alignment, commonly known as bowlegs.
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Valgus (Knock-knees): If the line passes lateral (outside) to the center of the knee, it signifies a valgus alignment, often called knock-knees.
This method provides a clear and standardized way to determine knee alignment, aiding in the diagnosis and treatment of lower limb deformities.
