Meniscal tears, anterior cruciate ligament tears, petellar subluxation and patellar tendonitis are common injuries to the human knee, according to WebMD. A meniscal tear is usually the result of twisting the knee, which can cause damage to the cartilage that cushions the knee, called the meniscus.
An ACL tear or strain occurs when the ligament is stretched or torn, which may result in a knee "giving out," as the ligament is responsible for the knee's stability. Patellar subluxation involves the kneecap dislocating or otherwise sliding abnormally along the thighbone. Patellar tendonitis is inflammation of the tendon that connects the kneecap to the shin bone. This most commonly occurs in athletes who frequently jump, claims WebMD