The association between loss of ankle dorsiflexion range of movement, and hip adduction and internal rotation during a step down test

A pattern of excessive hip adduction and internal rotation with medial deviation of the knee has been associated with numerous musculo-skeletal dysfunctions. Research into the role that ankle dorsiflexion (DF) range of motion (ROM) play in lower limb kinematics is lacking. The objective of this cross-sectional, observational study was to investigate the relationship between ankle DF ROM, and hip adduction and hip internal rotation during a step-down test with and without heel elevation in a healthy female population. Hip and ankle ROM was measured kinematically using a ten-camera Optitrack motion analysis system. Thirty healthy female participants (mean age = 20.4 years; SD = 0.9 years) first performed a step-down test with the heel of the weight bearing foot flat on the step and then with the heel elevated on a platform. Ankle DF, hip adduction and hip internal rotation were measured kinematically for the supporting leg. Participants who had 17° or less of ankle DF ROM displayed significantly more hip adduction ROM (p = 0.001; Cohen's d effect size = 1.2) than the participants with more than 17° of DF during the step-down test. Participants with limited DF ROM showed a significant reduction in hip adduction ROM during the elevated-heel step-down test (p = 0.008). Hip internal rotation increased in both groups during the EHSD compared to the step-down test (p > 0.05) Reduced ankle DF ROM is associated with increased hip adduction utilised during the step-down test. Ankle DF should be taken into account when assessing patients with aberrant frontal plane lower limb alignment.