Hamstring spasticity assessment: does the hip flexion angle impact outcomes?

Purpose: Hamstring spasticity is prevalent following neurological injury. The standardized assessment involves passive knee extension, in a position of 90° hip flexion. This creates passive insufficiency of the muscle and lacks ecological validity for walking, whereby the hip typically flexes to a maximum of 40° during swing phase, while the knee extends. This study compared assessment outcomes when completed in 40° and 90° hip flexion. Methods: The Modified Ashworth Scale and Modified Tardieu Scale, were performed on 35 adults with a neurological condition. Each participant was assessed by three assessors, resulting in 105 trials at 40° and 90°. Results: There was a significant increase in the proportion of trials rated as spastic using the Modified Ashworth Scale (p=.012, phi=.27), and Modified Tardieu Scale (p<.001, phi=.36), and the severity of spasticity using the Modified Ashworth Scale (p<.001, effect size (ES)=.50), and Modified Tardieu Scale (p<.001 ES=.47), at 90° hip flexion. The angle of reaction occurred 32° earlier at 90° hip flexion (p<.001, ES = 1.61). Conclusions: Completing hamstring assessments in 40° hip flexion may reduce the passive insufficiency and improve the ecological validity of assessment, for walking. This may assist in the selection of patients requiring intervention, when their goal relates to walking.