Knee not straight may be caused by the following reasons: First, the presence of internal joint adhesions, common in patients with injuries around the knee joint; for example, fractures, dislocations in the recovery process due to long-term braking, resulting in scar adhesions within the joint, if the patient does not actively functional exercise, will gradually make the joint adhesions aggravated, and finally lead to patients with limited extension, that is, the knee joint Second, there may be a bony deformity, such as a serious peripheral fracture that has not been properly treated, which may leave a bony deformity, causing the patient to straighten the knee, but the knee is still not straight from the surface; third, it may be caused by soft tissue contracture at the back of the knee, which is also caused by prolonged braking of the knee joint; due to The knee joint is braked in a flexed position for a long period of time, thus causing contracture of the posterior soft tissues, such as tendons or fascia, which can lead to limited extension in the long term. This can also occur if the soft tissues on the posterior side become contracted due to factors such as burns.