Use of the normalcy index for the evaluation of gait pathology.

The normalcy index (NI) has been proposed as a method for quantifying the amount of deviation in a subject's gait, compared to the gait of the average unimpaired person. The NI was computed for a sample of 144 children affected by cerebral palsy, five idiopathic toe-walkers and 12 able-bodied subjects. It was sensitive enough to distinguish unimpaired subjects from idiopathic toe-walkers and to distinguish between the plegic and uninvolved limbs of hemiplegic patients. The NI was robust enough to categorize pathology, ranging from mild disorders to quadriplegia. The NI was found to be clinically applicable, reliable and easy to use, making it a valuable element in the quantitative evaluation of gait pathology.