Determination of the thigh-foot angle

The thigh-foot angle (TFA) is the angular difference between the axis of the foot and thigh when the patient is in a prone position with the knees flexed 90 degrees and the foot and ankle are in neutral position. The TFA is external (or positive) when the foot points away from the midline (left) and internal (or negative) when the foot points toward the midline (right). The TFA normally ranges from +10 to +15 degrees.