There are four major ligaments in the knee. Ligaments are elastic bands of tissue that connect bones to each other and provide stability and strength to the joint. The four main ligaments in the knee connect the femur (thighbone) to the tibia (shin bone), and include the following:
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anterior cruciate ligament (ACL) – the ligament, located in the center of the knee, that controls rotation and forward movement of the tibia (shin bone).
posterior cruciate ligament (PCL) – the ligament, located in the center of the knee, that controls backward movement of the tibia (shin bone).
medial collateral ligament (MCL) – the ligament that gives stability to the inner knee.
lateral collateral ligament (LCL) – the ligament that gives stability to the outer knee.
The anterior cruciate ligament (ACL) is one of the most common ligaments to be injured. The ACL is often stretched and/or torn during a sudden twisting motion (when the feet stay planted one way, but the knees turn the other way). Skiing, basketball, and football are sports that have a higher risk of ACL injuries.
The posterior cruciate ligament (PCL) is also a common ligament to become injured in the knee. However, the PCL injury usually occurs with sudden, direct impact, such as in a car accident or during a football tackle.
Often, a cruciate ligament injury does not cause pain. Instead, the person may hear a popping sound as the injury occurs, followed by the leg buckling when trying to stand on it, and swelling. However, each individual may experience symptoms differently.
The symptoms of a cruciate ligament injury may resemble other conditions or medical problems. Always consult your physician for a diagnosis.
The medial collateral ligament is injured more often than the lateral collateral ligament. Stretch and tear injuries to the collateral ligaments are usually caused by a blow to the outer side of the knee, such as when playing hockey or football.