Gait analysis before and after unilateral total knee arthroplasty. Study using a linear regression model of normal controls -- women without arthropathy.

Stepwise multiple regression analysis (forward method) was performed with 22 gait variables obtained from the free and slow gait of 35 normal controls (women without knee arthropathy). These 22 variables were target variables, and velocity, age, body height, and body weight were explanatory variables. Velocity showed the greatest effect on the gait variables, followed by weight, age, and height. Of the 22 target variables, 16 could be explained by a significant level of difference of P < 0.01. A linear regression model of normal gait was then established, based on the judgment that these 16 gait variables were greatly affected by four variables -- velocity, age, height, and weight. Since this model does not perfectly represent the observed values, we compared the observed value/predicted value ratios in different groups to compensate for their differences. The free gait velocity in 20 osteoarthritic patients, 1 year or more after unilateral total knee arthroplasty (TKA), and who had no pain in the contralateral knee was lower than in the normal controls. In comparisons using linear regression models, step length was shorter, step width was longer, and gait cycle was shorter than in controls. Single support time was shorter and double support time was longer. Of the ground reaction forces, the first peak of the vertical component and the peak of the driving force of the fore-aft component were smaller than in controls. The total range of motion (TRM) in the stance phase was less than in controls. These results show quantitatively not only that the velocity of gait after TKA is lower than in normal controls, but also that gait patterns are different. In eight osteoarthritic patients assessed before and after TKA, and who had no pain in the contralateral knee, free gait velocity increased 6 months post-operation, but showed no further changes at 1 year. A linear regression study comparing the gait before TKA and 6 months post-TKA revealed that step time, single support time, double support time, and step width, and -- with regard to ground reaction forces -- the peaks of the driving force and the braking force of the fore-aft component, and TRM in the stance phase all approached the levels in the normal controls. No further changes were observed 1 year postoperatively. Although our models were not perfect, we were able to clarify the differences in gait variables between a TKA group and normal controls and the improvements from pre- to post TKA by normalizing the influence of the four independent variables, (velocity, age, weight, and height) with particular emphasis on gait velocity.