The knee is one of the most commonly injured parts of the body. Sports, falls, and motor-vehicle accidents account for the vast majority of knee pain and injuries to the knee.
The different types of common knee injuries to the knee are defined by the affected anatomy of the knee and the mechanism by which it's injured.
Knee sprains are injuries to the ligaments that hold the knee together. There are multiple ligaments that stabilize the knee and keep it in alignment.
The anterior cruciate ligament (ACL) and the posterior cruciate ligament (PCL) stabilize the knee in movement from front to back and cross each other in the middle of the knee joint. The medial collateral ligament (MCL) and lateral collateral ligament (LCL) stabilize the knee so that the bones do not slide from side to side.