Name: Anterior Cruciate Ligament Injury

Description: Torn ACL

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The knee is essentially a modified hinge joint located where the end of the thigh bone (femur) meets the top of the shin bone (tibia). Four main ligaments connect these two bones:

  • Medial collateral ligament (MCL) -- runs along the inner part of the knee and prevents the knee from bending inward.
  • Lateral collateral ligament (LCL) -- runs along the outer part of the knee and prevents the knee from bending outward.
  • Anterior cruciate ligament (ACL) -- lies in the middle of the knee. It prevents the tibia from sliding out in front of the femur, and provides rotational stability to the knee.
  • Posterior cruciate ligament (PCL) -- works with the ACL. It prevents the tibia from sliding backwards under the femur.

The ACL and PCL cross each other inside the knee, forming an "X."

The ACL is the most commonly injured ligament in the knee. It can be torn when a
twisting force is applied to the knee while the foot is firmly planted on the ground or upon landing, or from a direct blow to the knee, usually to the outside of the knee, as may occur during a football tackle. The most common sports where ACL injuries occur are soccer, basketball, tennis, volleyball and skiing. ACL injuries are more common in women for a variety of reasons including anatomical difference and the effect of female hormones on the joints.
The symptoms of a torn ACL include:

  • An audible pop or crack at the time of the injury
  • Inability to stand of the leg with a feeling of joint instability
  • Extreme pain and knee tenderness
  • Knee swelling
  • Decreased ability to move the knee

As with most such injuries, care immediately after the injury consists of RICE therapy-
Rest, Ice, Compression, and Elevation). Medical attention should be sought to thoroughly evaluate the injury. If the tear is mild and not completely through the entire ligament, conservative management including immobilization with a knee brace and physical therapy may surfice. If the ligament is completely torn, it can not be repared, but must be replaced, usually during arthroscopic surgery.

Bookmarks The following information, which has been distilled by the casebook author from this and other websites is particularly relevant to this casebook.
Bookmarks - Web
Web Page Notes Concepts
 Anterior cruciate ligament injuries - ACL Overview of ACL injury
 Anterior cruciate ligament (ACL) injury: MedlinePlus Medical Encyclopedia Good overview from Medline Plus with good diagrams
 Q&A About Knee Problems Good overview of knee problems
 Anterior cruciate ligament - Wikipedia, the free encyclopedia Brief overview

This web-site is for informational purposes only and is not intended as a substitute for advice from your doctor. It should not to be used for self-diagnosis or treatment.