An anterior cruciate ligament injury is the over-stretching or tearing of the anterior cruciate ligament (ACL) in the knee. A tear may be partial or complete.

Cruciate ligament injury - anterior; ACL injury; Knee injury - anterior cruciate ligament (ACL)

The knee is similar to a 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 (side) of the knee and prevents the knee from bending inward.
• Lateral collateral ligament (LCL) -- runs along the outer part (side) 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.

Images

ACL injury

Arthroscopy

ACL degrees

Anterior cruciate ligament (ACL) injury

Normal knee anatomy

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Review Date: 08/26/2009
Reviewed By: Dennis Ogiela, MD, Orthopedic Surgeon, Danbury Hospital, Danbury, CT. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org)