Effects of neuro-developmental treatment and orthoses on knee flexion during gait: a single-subject design. The interactive effects of neuro-developmental treatment and inhibitive ankle-height orthoses on gait were examined via a single-subject research design. Knee flexion during gait at initial contact, mid-stance, heel-off, and mid-swing were measured in a 2-year-old girl with diplegia by use of a goniometer and freeze-frame videography. During the treatment and treatment/orthoses phases, a decrease in excessive knee flexion was noted. Changes in trend over time were greater in the 3-week treatment phase than in the 3-week treatment/orthoses phase. Changes in level at the initiation of the treatment/orthoses phase were greater than in the treatment phase. The described neuro-developmental treatment activities were conducted correctly 92% of the time according to an independent observer. The interrater reliability of goniometric data measured by videography was .93 using intraclass correlation coefficients. The results of this study suggest that both methods of treatment can be used to decrease excessive knee flexion during gait in a child with diplegia. 