Classifications of gait patterns in spastic diplegia have been either qualitative, based on clinical recognition, or quantitative, based on cluster analysis of kinematic data. Qualitative classifications have been much more widely used but concerns have been raised about the validity of classifications, which are not based on quantitative data. We have carried out a cross-sectional study of 187 children with spastic diplegia who attended our gait laboratory and devised a simple classification

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... sagittal gait patterns based on a combination of pattern recognition and kinematic data. We then studied the evolution of gait patterns in a longitudinal study of 34 children who were followed for more than one year and demonstrated the reliability of our classification. Children with spastic diplegia usually walk independently but most have an easily recognised disorder of gait which may include deviations in the sagittal plane such as toewalking, flexed-stiff knees, flexed hips and an anteriorly tilted pelvis with lumbar lordosis. 1 When compared with their peers many also walk at a reduced speed, with increased energy expenditure and impaired functional capability. [2] [3] [4] Instrumented gait analysis gives detailed information and quantitative measurements. By a process of clinical interpretation this may help the clinician to understand the gait pattern and perhaps to plan appropriate intervention. 5,6 However, experienced clinicians often describe gait patterns using a combination of clinical examination and clinical observation. In 1986, Rang, Silver and De La Garza 7 described a number of gait patterns in spastic diplegia and classified them on a purely observational basis, related to spasticity or contracture of muscles which work in the sagittal plane. They observed associations between contractures of the psoas and lumbar lordosis, of the adductors and scissoring, of the hamstrings and knee flexion, of rectus femoris and stiff knee gait and of gastrocsoleus and tip-toe gait. By linking these observed patterns to specific shortening of the muscles, the association with management was implied. 7 In 1993, Sutherland and Davids 8 described four typical abnormalities of gait affecting the knee in children with spastic diplegia, namely jump knee, crouch knee, stiff knee and recur-vatum knee. Although these patterns were illustrated by sagittal plane kinematic data, no information was given regarding the quantitative assessment of the individual patients in the study and there was no discussion of any deviation of gait at other anatomical levels. Since these two landmark studies, Miller et al 1 have further elaborated on the sagittal gait patterns originally described by Rang et al. 7 The five patterns were described as jump, crouch, equinus, jump plus equinus, and recurvatum plus equinus. A number of authors 9-11 have taken a different approach and have used cluster analysis techniques to classify gait patterns in cerebral palsy on a purely quantitative basis. While the patterns identified by cluster analysis appear to have statistical validity, none has become widely accepted or is regularly used by clinicians. Our aim was to combine pattern recognition and quantitative kinematic data in order to devise a clinically useful classification of sagittal gait patterns in spastic diplegia. We planned to develop a template for describing sagittal gait patterns to evaluate muscletendon surgery and orthoses in the management of spastic diplegia. Our study was made in three inter-related parts. The first was a cross-sectional study of gait patterns in children with spastic diplegia. We then carried out a longitudinal study of a subset of patients who had had more than one instrumented gait analysis. Finally, we investigated the intraand inter-observer reliability of the classification.