An examination of the relationship between dynamic knee joint stiffness and gait pattern of children with cerebral palsy

Dynamic joint stiffness represents the resistance that a joint opposes to an applied moment. Stiffness arises in conditions of joint laxity, instability and increased co-contraction and is commonly utilized as a means to stabilize the joint. The knee joint seems to be crucial for determining the walking pattern. The aim of this study was to investigate the association between the gait pattern, globally quantified by the Gait Profile Score (GPS), which indicates the 'quality' of a particular walking strategy, and knee dynamic joint stiffness (Kk) in children with diplegia. Kk is expressed by plotting the values of the knee flexion-extension moment versus the knee flexion-extension angle during weight acceptance. In this interval, the linear regression was fitted. The angular coefficient of the linear regression corresponded to the joint stiffness index. Sixty-one children with diplegia and 18 healthy individuals took part in this study. From their gait analysis data, the GPS (with its Gait Variable Scores-GVSs) and the Kk were calculated. Data showed that GPS (p = 2.73 × 10−21) and GVSs values for the patients with diplegia were higher in comparison to healthy controls. The Kk values for patients were not statistically different from those of controls. The correlation between Kk and GPS did not show the presence of any significant relationship (r = −0.04; p > 0.05). Thus, the functional limitation in diplegic children does not seems to be strictly related to Kk.