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Ligament injuries in the knee - such as an anterior cruciate ligament (ACL) -- are dreaded by professional and amateur athletes alike. They can be painful and debilitating. They can even permanently change your lifestyle.

But there's good news. While an ACL injury or other ligament damage once ended the career of many an athlete, treatment has become much more successful.

brace on knee

So what's behind these feared injuries? Ligaments are tough bands of tissue that connect the bones in your body. Two important ligaments in the knee, the ACL and posterior cruciate ligament (PCL), connect the femur or thigh bone with the tibia, one of the bones of the lower leg. Too much stress on these ligaments can cause them to stretch too far -- or even snap.

ACL injury and other ligament injuries can be caused by:

  • Twisting your knee with the foot planted
  • Getting hit on the knee
  • Extending the knee too far
  • Jumping and landing on a flexed knee
  • Stopping suddenly when running
  • Suddenly shifting weight from one leg to the other

These injuries are common in soccer players, football players, basketball players, skiers, gymnasts, and other athletes.

There are four ligaments in the knee that are prone to injury:

  • Mentioned above, the anterior cruciate ligament (ACL) is one of the two major ligaments in the knee. It connects the thigh bone to the shin bone in the knee. ACL injuries are a common cause of disability in the knee. In the U.S., 95,000 people get them every year. They are more common in women than men.
  • The posterior cruciate ligament (PCL) is the second major ligament in the knee connecting the thigh bone to the shin bone in the knee.
  • The lateral collateral ligament (LCL) connects the thigh bone to the fibula, the smaller bone of the lower leg on the lateral or outer side of the knee.
  • The medial collateral ligament (MCL) also connects the thigh bone to the shin bone on the medial or in side of the knee.

What Does a Knee Ligament Injury Feel Like?

An ACL injury -- or other ligament injury -- is sometimes hard to diagnose. Symptoms of a knee ligament injury are:

  • Pain, often sudden and severe
  • A loud pop or snap during the injury
  • Swelling
  • A feeling of looseness in the joint
  • Inability to put weight on the point without pain

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