The aim of the study was to investigate the effect of the spinal tap test on sit-to-stand (STS), walking, and turning and to determine the relationship among the outcome measures of STS, walking, and turning in patients with iNPH. Twenty-seven patients with clinical symptoms of iNPH were objectively examined for STS, walking, and turning by the Force Distribution Measurement (FDM) platform connected with a video camera. Assessments were performed at before and 24 hours after spinal tap. Motor abilities were assessed by the STS time, time of walking over 3 meters, and time and number of steps when turning over 180 degrees. Significant improvements were found in the STS time (p = 0.046), walking time (p = 0.048), and turning step (p = 0.001). In addition, turning time was improved but not statistically significant (p = 0.064). Significant relationships were found among all outcome measures (p < 0.001). The relationship among these outcome measures indicated that the individuals had similar ability levels to perform different activities. This may serve as a new choice of outcome measures to evaluate the effect of intervention in different severity levels of patients with iNPH.