Kinematics and kinetics of the lower limb and pelvis during step descent in individuals with limited ankle dorsiflexion.

BACKGROUND

Adequate ankle dorsiflexion is required during step descent to allow controlled forward progression of the body over the support limb. It remains unclear how limited passive ankle dorsiflexion range of motion (ADF-ROM) influences lower-limb and pelvis biomechanics during this task.

RESEARCH QUESTION: Is lower ADF- ROM associated with lower-limb kinematics and kinetics during step descent?

METHODS

In this cross-sectional study, 40 individuals were divided into lower ADF-ROM (< 10º) and higher ADF-ROM (≥ 15º) groups based on the plantar flexor flexibility test. The step descent activity was assessed using a three-dimensional motion analysis system. Group characteristics, passive ADF-ROM, cycle duration, time to heel-off, and peak ankle dorsiflexion were compared using unpaired t-tests. One-dimensional Statistical Parametric Mapping unpaired t-tests were used to compare joint angles and internal joint moments during the task.

RESULTS

Compared with the higher passive ADF-ROM group, individuals with lower ADF-ROM showed lower peak ankle dorsiflexion, earlier heel-off, reduced foot, knee, and hip flexion-related motion, greater knee and hip lateral rotation, and a foot motion pattern suggestive of greater pronation (greater rearfoot-shank eversion and midfoot-rearfoot eversion and abduction). No differences in pelvis movement were observed. They also exhibited higher plantar flexor moment and lower knee medial rotator moment during final landing. Most between-group differences showed large effect sizes.

SIGNIFICANCE: Reduced passive ADF-ROM was associated with compensatory multisegment foot and lower-limb motion during step descent, including greater pronation-related foot motion, reduced knee and hip flexion-related motion, and altered ankle and knee kinetics during final landing.