The clinician palpates the position of the navicular tubercle as the patient’s foot is non–weight-bearing but resting on the floor surface, with the subtalar joint maintained in neutral.
The clinician then attempts to quantify the amount of inferior displacement of the navicular tubercle, as the patient assumes 50% weight-bearing on the tested foot (relaxed standing).
The two measurements are recorded.
What is a positive Navicular Drop Test?
A navicular drop that is greater than 10 mm from the neutral position to the relaxed standing position suggests excessive medial longitudinal arch collapse of abnormal pronation.
This test has been found to have an intratester reliability that ranged from ICC = 0.61 to 0.79 and intertester reliability of ICC = 0.57.
However, it is questionable whether a significant drop is also indicative of dysfunction.
Feiss Line Test
The Feiss line test is used to assess the height of the medial arch, using the navicular position.
With the patient non–weight-bearing, the clinician marks the apex of the medial malleolus and the plantar aspect of the first MTP joint, and a line is drawn between the two points. The navicular is palpated on the medial aspect of the foot, and an assessment is made of the position of the navicular relative to the imaginary line. The patient is then asked to stand with their feet approximately 3–6 inches apart.
In weight-bearing, the navicular normally lies on or very close to the line.
The degree of flatfoot deformity is defined as following:
If the navicular falls one-third of the distance to the floor, it represents a first-degree flatfoot;
if it falls two thirds of the distance, it represents a second-degree flatfoot;
if it rests on the floor, it represents a third-degree flatfoot.
No diagnostic accuracy studies have been performed to determine the sensitivity and specificity of this test.
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