The Salford Gait Tool (SF-GT) assesses the position of the hip, knee and ankle at six gait events of the gait cycle using a 5-point grading system. Each grade (5 grades for each joint, −2 to +2 including 0), corresponds to a specific range of angular positions. For example, grade 1 hip corresponds to 15–45° hip flexion. These ranges of angular positions were then calibrated using kinematic gait data of 13 gait clusters derived from cluster analysis on 67 children with CP and normal gait styles. (Toro B, et al. Gait Posture, in press.)
Reference: Brigitte Toro, Christopher J. Nester and Pauline C. Farren. The Salford Gait Tool (SF-GT). Gait & Posture Volume 24, Supplement 2, December 2006, Pages S250-S251.
This article is based on the validity and reliability of Salford Gait Tool.
I think complete explanation of this scale will be coming in the new article which is in press right now.
Hope this might help for now. If I come across complete scale I will let you know.