Assessing a Clinical Test of Ankle Joint Range of Motion: Influence of Variations in Foot and Tibia Length

The weight-bearing lunge test (WBLT) is a simple, reliable, and clinically-useful method for measuring of ankle dorsiflexion range of motion.1 During the test, the patient stands with the big toe of one foot 10 cm from a wall and then attempts to push their knee forward to contact the wall.2 Patients with inadequate ankle dorsiflexion range of motion will not be able to touch their knee to the wall, suggesting a bony, ligamentous, or muscular restriction at the ankle. The final goal of the test is to find the maximum distance from the wall in which a patient can still touch their knee to the wall without lifting their heel off the ground. This “distance-to-wall” measurement quantifies the ankle dorsiflexion range of motion in a simple, cheap, and minimally invasive manner. Clinicians can also use the WBLT to assess asymmetries in ankle dorsiflexion ROM within an individual, with a 1.5 cm difference (in the “distance-to-wall” measurement) between the left and right legs reported as the clinically relevant threshold.3 However, interpretation of the WBLT may be affected by the length of the patient’s foot and tibia, which is not accounted for in the normative values.1 A patient with a long foot and relatively short tibia should theoretically perform better (distance to the wall is greater) on the test than a patient with a short foot and relatively long tibia. Other measurements collected from the WBLT are less affected by these factors, such as the tibial inclination angle or the trigonometric calculation of the ankle angle from measured distance,4,5 however, the distance from the wall to the big toe is the simplest method and is considered to be a clinically relevant outcome. Therefore, it is important to assess the factors that influence its interpretation and the level of influence that each factor has. Specific Aim: To investigate whether the lengths of the tibia and foot influence the distance-to-wall measurement in the weight-bearing lunge test. Hypothesis: A negative correlation will exist between the distance-to-wall measurement and the foot-shank ratio. Additionally, this correlation will be stronger than the correlation between the foot-shank ratio and the tibial inclination angle. This would demonstrate that the proportions of the foot and lower leg influence the distance-to-wall measurement