Since July 2019， 64 patients with knee hyperextension after stroke were selected and randomly divided into low ratio group， middle ratio group， high ratio group， and random ratio group according to the block random method （the length of block was 8）. During the treatment， a total of 4 patients （1 in low ratio group，1 in high ratio group and 2 in random ratio group） were withdrew from the study because of early discharge. A total of 60 patients （15 in low ratio group，16 in middle ratio group， 15 in high ratio group， and 14 in random ratio group） completed the study. On the basis of routine rehabilitation training， all the patients in various groups received isokinetic muscle strength training. The muscle strength ratio of knee flexors and extensors in low ratio group was controlled at 0.5－0.7，in middle ratio group it was controlled at 0.7－0.9，and in high ratio group it was controlled at 0.9－1.1.The ratio of flexor muscle to extensor muscles was 0.5－1.1 in random ratio group.Before treatment and 4 weeks after treatment， the knee hyperextension correction rate and simplified Fugl Meyer Assessment（FMA） scale were used to evaluate the effective rate of knee hyperextension and lower limb motor function of the patients in various groups. CON-TREX multi joint isokinetic muscle strength test and training system was used to compare the average torque of knee flexors and extensors of the patients in various groups.

Four weeks after treatment， the FMA scores of the patients in various groups were higher than those before treatment （P<0.05）， the effective rate of knee hyperextension of the patients in middle ratio group was significantly higher than that in the other groups （P<0.0083）， and the FMA score was also significantly higher than that in the other groups （P<0.05）. Four weeks after treatment， compared with low ratio group， the ratios of knee flexor to knee extensor of the patients in middle ratio group and high ratio group were increased （P<0.05）， and the ratio of knee flexor to knee extensor of the patients in random ratio group was decreased （P<0.05）； compared with middle ratio group， the ratio of knee flexor to knee extensor of the patients in high ratio group was increased （P< 0.05）， and the ratio of knee flexor to knee extensor of the patients in random ratio group was decreased （P<0.05）； compared with high ratio group， the ratio of knee flexor to knee extensor of the patients in random ratio group was decreased （P<0.05）.

The isokinetic muscle strength training with the muscle strength ratio of knee flexor and knee extensor between 0.7 and 0.9 can more effectively correct the knee hyperextension after stroke.