OBJECTIVE: To assess the reliability and validity of a newly described 
classification of sagittal plane alignment in spastic diplegic gait.
DESIGN: Twenty split-screen videos of children with spastic diplegia, Gross 
Motor Function Classification System levels I to III, were viewed on 2 
occasions, 6 weeks apart, by 5 raters. The sagittal plane alignments of the 
right and left lower limbs in gait were classified separately as true equinus, 
jump knee, apparent equinus, or crouch, based on the published classification. A 
fifth category, nonclassifiable, was used if classification was not possible. We 
then used sagittal plane kinematic data to confirm the classification for each 
subject and these were compared with rater classification scores, which used the 
video information only.
SETTING: Tertiary-level children's hospital.
PARTICIPANTS: Three pediatric orthopedic surgeons and 2 pediatric orthopedic 
residents.
INTERVENTIONS: Not applicable.
MAIN OUTCOME MEASURES: Gait classification scores derived from visual 
observation were compared among and within raters. The gait classification 
scores derived from visual observation were compared with the scores derived 
from sagittal plane kinematic data to assess validity.
RESULTS: A moderate correlation was found among the 5 raters within each 
session, with an interrater weighted kappa score of .45 in session 1 and .49 in 
session 2. The intrarater, weighted kappa scores showed a moderate to 
substantial level of agreement between sessions, ranging from .50 to .68. The 
classification scores of individual raters had moderate validity when compared 
with classifications derived from the sagittal plane kinematic data. However, 
there was a substantial level of agreement between the consensus opinion and the 
classification obtained using the kinematic data as well as the video recordings 
(weighted kappa=0.8).
CONCLUSIONS: This classification has only moderate reliability and validity when 
a single experienced rater views the 2-dimensional gait videos. However, the 
consensus opinion derived from the scores of 5 raters considerably improves the 
validity of the assessment.