When a femoral neck fracture is treated with internal fixation, the action of straightening and lifting the leg on your own initiative is absolutely not allowed. How many times the force of the leg is our hip joint when we straighten and lift the leg? If a person weighs 70 kg, the weight of one thigh is about 1/5 of the weight, which is about 14 kg. And in straightening the leg lift the hip joint to withstand the force is 1.5 times the weight of the leg, 14 kilograms of 1.5 times is about 21 kilograms, which 21 kilograms of force is how big? Let’s think about the water fountain with a bucket is 10 liters, 10 kg, that is, two buckets so heavy. We use three nails to fix the weight of two buckets of water, is very, very difficult, so this action is very dangerous. How much force can these three nails actually withstand? If a patient with a femoral neck fracture does horizontal flexion and extension in the lateral position, this force is not a problem, because the horizontal flexion and extension of the joint withstands a force of 3-5 kg, and the difference between 3-5 kg and 21 kg is very big. Therefore, the action of straightening and lifting the leg on one’s own initiative is definitely a contraindication to the activity for patients receiving internal fixation treatment for femoral neck fractures. Therefore, hip flexion activity must be a passive activity done with the help of others, and absolutely no force should be exerted by oneself.