The aim of this paper is to study the relation between muscles electrical activity and knee movement during walking for patient with patellafemoral pain by measurement both of electromyography (EMG) and changing of knee angle by electro-goniometer. The start and end of the gait cycle were determined by foot sensors, A program was designed for signal processing of the data, Testes were carried out at Hamish hospital in Damascus. Subjects were divided into two groups: 46 normal subjects and 21 patient. Final results also showed that hamstring group activity and galf group activity decreases during stance phase because knee cancel it first flexion with increase in quadriceps femoris activity to keep extension of knee. In swing phase, it is noted that the decrease in knee flexion and it depends on the increase in quadriceps femoris activity in all the period of swing phase, but hamstring group activity increases to keep hip instability, that is, it responds to increase activity of quadriceps femoris with less knee flexion. The activity of subject muscles in the period of gait cycle is less than normal muscles.