How Much Does the Talocrural Joint Contribute to Ankle Dorsiflexion Range of Motion During the Weight-Bearing Lunge Test? A Cross-sectional Radiographic Validity Study.

Abstract

Ankle dorsiflexion range of motion is commonly measured during the weight-bearing lunge test (WBLT) as the horizontal knee distance traveled or tibial inclination. These measures are assumed to represent talocrural dorsiflexion, yet have not been validated against radiographic images. To determine the (1) contribution of the talocrural joint to tibial inclination during the WBLT, (2) validity of inclinometer and photographic measures of tibial inclination compared to radiographic images, and (3) the association between tibial inclination and horizontal distance measures. Tibial inclination using an inclinometer, horizontal distance via a ruler, and radiographic and photographic images were recorded in 20 participants in standing and during the end-range WBLT. Two assessors used computer software to measure talar rotation and tibial inclination from digital radiographs and photographs. The limits of agreement between photographic and inclinometer measures compared to radiographic measures, as well as correlations between measures, were calculated. In the end-range WBLT, 91.8% of motion occurred at the talocrural joint, with 8.2% occurring distally. There were very strong correlations (all, r 0.88, P<.001) between end-range radiographic and photographic measures, radiographic and inclinometer measures, and radiographic, inclinometer, and photographic measures of tibial inclination and horizontal lunge distance. Calculation of the limits of agreement indicated unacceptable agreement between inclinometer and radiographic measures (-7.84°, 5.92°) and acceptable agreement between photographic and radiographic measures (-2.17°, 2.49°). Tibial inclination during the WBLT primarily occurs at the talocrural joint. While inclinometer and photographic measures of tibial inclination can reliably be used clinically to measure dorsiflexion range of motion during the WBLT, inclinometer results differ slightly from those obtained via radiographs. J Orthop Sports Phys Ther 2019;49(12):934-941. Epub 23 Jul 2019. doi:10.2519/jospt.2019.8697.