There are complete and incomplete patellar ligament injuries, which include pain, inability to flex and extend the knee, accompanied by knee swelling and pain, and weakened or disappeared knee reflex. 1. Incomplete injury: this kind of patient manifests as knee joint swelling and pain, knee joint can be flexed and extended, but the pain is obvious when straightening the knee joint, or accompanied by straightening the knee joint with reduced strength, the patellar ligament around the stopping point of the pressure and pain is obvious, and the knee reflex is weakened. 2. Complete injury: most of these patients are unable to flex and extend the knee joint, after passive flexion of the knee joint, unable to straighten the knee joint, obvious swelling and pain in the knee joint, obvious pressure and pain around the attachment point of the patellar ligament, and disappearance of the knee reflex. For patellar ligament injury to determine its severity, the systematic examination is one aspect, but also need to be combined with imaging examination, so it is important to go to the hospital in time to improve the relevant examination.