The symptoms of a knee ligament tear are severe pain and swelling of the knee, according to the American Academy of Orthopaedic Surgeons and MedlinePlus. The patient might also hear a "pop" when the injury occurs, and the knee is unstable and painful when the patient attempts to put weight on it. The knee might feel vulnerable to giving out when the patient tries to walk.
The knee is supported by cruciate and collateral ligaments, says MedlinePlus. While all are subject to injury, the injury may come about in different ways. An injury to the anterior cruciate ligament usually happens when the patient receives a hard blow to the side of his knee. It can also come about because the knee was overextended or the patient abruptly stopped moving in one direction and turned to move in another. An ACL injury usually occurs with a torn medial collateral ligament or an injury to the meniscus. Though an ACL injury is a common injury of football players, women are more likely to have one.
Injuries to the collateral ligaments happen when the knee is pushed violently sideways, or from a blow to the outside of the knee, claims the Academy of Orthopaedic Surgeons. Injuries to the posterior cruciate ligament are not common and require a powerful blow to the front of the knee, says the AAOS. Like the ACL, this injury often occurs with other injuries to the knee.