Knee ligament injury

A knee ligament injury is an injury to one or more of the four primary ligaments in your knee. Ligament injuries to the knee are very common in sports that require stopping and starting or quickly changing directions. Ligaments are strong, fibrous rope-like bands that hold the bones of your knee joint together.

The knee is the largest and most complex joint in your body, because it joins three bones — your thighbone (femur), shinbone (tibia) and kneecap (patella). The four ligaments that keep your knee bones positioned and functionally properly are:

  • Collateral ligaments – The medial collateral ligament (MCL) is on the inner side of your knee, and the lateral collateral ligament (LCL) is on the outer side of your knee. Together they control sideway motions and keep your knee within a safe range of motion. The MCL ligament is one the most often injured knee ligaments.
  • Cruciate ligaments – These two ligaments inside your knee joint cross one another, forming an "X." The anterior cruciate ligament (ACL) crosses in front, while the posterior cruciate ligament (PCL) crosses in back. An ACL injury is a common cause of disability in the knee. The American Academy of Orthopaedic Surgeons (AAOS) reports that 95,000 people (more women than men) get ACL injuries every year.


Depending on the ligament or ligaments that are involved, you may feel one or more of these symptoms of knee ligament injury:

  • Pain, often sudden and severe
  • A loud pop or snap during the injury – common in ACL and PCL injuries
  • Swelling
  • A feeling of looseness in your knee joint
  • Inability to put weight on the knee without pain


Knee ligament injuries are common sports injuries that happen to gymnasts, skiers and athletes who play soccer, football and basketball and other sports that require a lot of pivoting. In addition to a direct blow to your knee, the following actions can cause a knee ligament injury:

  • Twisting your knee with your foot planted
  • Extending your knee too far
  • Jumping and landing on your knee while it’s flexed
  • Stopping suddenly when you're running
  • Suddenly shifting your weight from one leg to the other


An injury to a ligament is called a "sprain," not to be confused with a muscle "strain." The three types of ligament sprains are measured by severity:

  • Grade 1 sprains – Mildly damaged and slightly stretched, the ligament is able to keep the knee joint stable.
  • Grade 2 sprains – Referred to as a partial tear of the ligament, it is stretched to the point where it becomes loose.
  • Grade 3 sprains – Also known as a complete tear, the ligament has been split in two, leaving the knee joint unstable.


If you injure any knee ligament, it is recommended that you seek an orthopaedic consultation, as the range of treatment varies significantly depending on the type of injury sustained as well as the severity. For example, a mild-to-moderate collateral knee ligament injury may heal on its own in time with nonsurgical approaches such as anti-inflammatory medications, physical therapy and the RICE regimen (Rest, Ice, Compression, Elevate). If your injury is more severe, you may require knee ligament repair surgery or knee reconstruction surgery. When injured, the cruciate ligaments tend to require  reconstruction surgery. This is particularly true with the ACL, which requires reconstruction to restore normal knee motion and prevent further damage to the knee.

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