Reliability of measurements obtained with the Modified Ashworth Scale in the lower extremities of people with stroke

Background and Purpose. Abnormal muscle tone is a common motor disorder following stroke, which may require rehabilitation. The Modified Ashworth Scale is a 6-point rating scale that is used to measure muscle tone. The interrater and intrarater reliability of measurements obtained with the scale remain equivocal. The purpose of this study was to investigate the reliability of measurements obtained with the scale in the lower limb of patients with stroke. Subjects. Twenty patients were tested 2 weeks after their stroke, and 12 patients were tested 12 weeks after their stroke. Methods. Gastrocnemius, soleus, and quadriceps femoris muscles on the hemiplegic side were tested. Results. Interrater reliability for 2 raters was poor, with a Kendall tau-b correlation for the combined muscle group of .062 (P=.461). For intrarater reliability, the Kendall tau-b correlation was .567 (P<.001). The agreement within one rater occurred mostly on the grade of 0. Discussion and Conclusion. The Modified Ashworth Scale yielded reliable measurements in the lower limb for a single examiner, and agreement was best on the grade of 0. The reliability between examiners was not good, which may bring into question the validity of measurements obtained with the scale.