Patients with hereditary spastic paraplegia (HSP) often resemble patients with 
mild spastic diplegia (SD), although their motor limitations differ. The aim of 
this study was to analyse quantitatively the gait of HSP and SD subjects in 
order to define the gait pattern in HSP and the differences between the two 
conditions. Fifteen subjects with HSP, 40 patients with SD and 20 healthy 
subjects underwent gait analysis (GA). The spatio-temporal and kinematic 
parameters at the proximal joints were found to be similar in HSP and SD, 
whereas the most significant differences were found at the knee and ankle 
joints. Both groups displayed a tendency for knee hyperextension in the 
midstance phase, but the duration of this hyperextension was longer in the HSP 
patients. This study shows that GA complements traditional clinical evaluations, 
making it possible to distinguish, clearly, between motor ability in HSP and in 
SD patients; the duration of the knee hyperextension during midstance was found 
to discriminate between the two gait patterns.