Femoral Tibial Angle

Weight-bearing imaging evaluates alignment while the lower limb is supporting load, providing a clinically relevant view of the knee and limb relationship. An anteroposterior radiograph allows the femoral and tibial anatomical axes to be represented in the same image. This supports consistent assessment of alignment and helps clinicians identify deviations that may be relevant to knee deformity or osteoarthritis.

A deviation in the measured relationship between the femoral and tibial axes is described as varus or valgus alignment. These terms provide a clinical classification for the direction of the alignment abnormality rather than treating the angle as an isolated number. Recording the classification helps characterize knee deformity and supports comparison during evaluation or treatment planning.

Side-to-side and longitudinal comparisons add context to a single measurement. Differences between limbs may reveal asymmetry, while changes over time can indicate progression or alteration in alignment. This approach is useful when monitoring growth-related alignment changes, assessing the course of knee deformity or osteoarthritis, or evaluating whether alignment has changed after treatment.

The measurement begins with an anteroposterior, weight-bearing radiograph of the lower limb. The femoral and tibial anatomical axes are then drawn on the image, and the angle formed where those axes intersect is evaluated. Using the same axis-based approach on comparable examinations permits clinicians to document alignment, compare limbs, and follow changes over time.

Clinicians can use the measurement when assessing knee deformity, osteoarthritis, and alignment changes associated with growth. It provides a quantitative way to describe the relationship of the femur and tibia rather than relying only on visual judgment. The result can therefore contribute to clinical assessment and help organize decisions about monitoring or corrective management.

Before corrective or joint-replacement surgery, the measurement helps quantify existing lower-limb alignment and can contribute to treatment planning. After surgery, repeated assessments provide a way to examine alignment outcomes using the same radiographic concept. Comparing the measured angle before and after intervention may show whether the intended alignment change was achieved or document residual deviation.