During patellar fracture surgery, the patient is given a supine position on the operating bed, with the heel elevated, so that the affected side of the knee is suspended, and the patella and patellar ligament are in a state of laxity, which is conducive to the repositioning and fixation of the broken end of the patellar fracture in the operation. As the internal fixation of patella is mostly fixed by Kirschner’s pin, tension band or patellar polymerizer. However, the knee extension force of the lower limb is very strong, if the fracture is heavily comminuted, it is recommended that the patient’s lower limb on the injured side should be kept in the straight position after the operation, with restricted activities for about three weeks, and external fixation with plaster cast if necessary. During this period, the operator or rehabilitator can assist the patient to perform knee flexion exercises in a pain-free state to avoid possible knee stiffness etc.