Anterior Cruciate Ligament Tear (Torn ACL)

  • Medical Author:
    Benjamin Wedro, MD, FACEP, FAAEM

    Dr. Ben Wedro practices emergency medicine at Gundersen Clinic, a regional trauma center in La Crosse, Wisconsin. His background includes undergraduate and medical studies at the University of Alberta, a Family Practice internship at Queen's University in Kingston, Ontario and residency training in Emergency Medicine at the University of Oklahoma Health Sciences Center.

  • Medical Editor: William C. Shiel Jr., MD, FACP, FACR
    William C. Shiel Jr., MD, FACP, FACR

    William C. Shiel Jr., MD, FACP, FACR

    Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

View the Least Effective Exercises Slideshow Pictures
Learn about rehabilitation and recovery time after surgery for a torn ACL.

Torn ACL & Surgery Recovery Time

For regular people and pseudo-athletes, the days after arthroscopic knee surgery are spent reducing knee swelling and starting range-of-motion exercises. This process is hampered by a couple of physiologic barriers.

Torn anterior cruciate ligament (ACL) facts

  • The anterior cruciate ligament is one of the four ligaments in the knee that provides stabilization for the knee joint.
  • Torn ACLs are a common knee injury.
  • An ACL tear or sprain occurs with a sudden change in direction or pivot against a locked knee.
  • A pop, followed by pain and swelling of the knee are the most common symptoms of an ACL tear.
  • Women are more likely to tear their ACL because of differences in anatomy and muscle function.
  • Treatment goals are to return the patient to his or her preinjury level of function. Arthroscopic surgery may be required to reconstruct the torn ligament.
  • It may take six to nine months to return to normal activity after an ACL injury.

What is the function of the knee joint?

The purpose of the knee joint is to bend and straighten (flex and extend), allowing the body to change positions. The ability to bend at the knee makes activities like walking, running, jumping, standing, and sitting much easier and more efficient.

The thighbone (femur) and the shinbone (tibia) meet the kneecap (patella) to form the knee joint. The rounded ends of the femur, or condyles, line up with the flat tops of the tibia called the plateaus. There are a variety of structures that hold the knee joint stable and allow the condyles and plateaus to maintain their anatomic relationship so that the knee can glide easily through its range of motion. The knee is a hinge joint, but there is also some rotation that occurs when it bends and straightens.

There are four thick bands of tissue, called ligaments, that stabilize the knee and keep its movement in one plane.

  • The medial collateral ligament (MCL) and the lateral collateral ligament (LCL) stabilize the sides of the knee preventing side-to-side buckling.
  • The anterior cruciate ligament (ACL) and the posterior cruciate ligament (PCL) form an X on the inside of the knee joint and prevent the knee from sliding back to front and front to back respectively.

The major muscles of the thigh also act as stabilizers: the quadriceps in the front of the leg and the hamstrings in the back.

A sprain occurs when a ligament is injured and the fibers are either stretched or torn. A first-degree sprain is a ligament that is stretched but with no fibers torn, while a second-degree sprain is a partially torn ligament. A third-degree sprain is a completely torn ligament.

Picture of the anterior cruciate ligament (ACL)
Picture of the anterior cruciate ligament (ACL)
Medically Reviewed by a Doctor on 3/18/2016
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