Athletes who participate in sports that place significant stress on their knees are susceptible to an injury to the anterior cruciate ligament. Among the most common causes are quick changes of direction, sudden stopping, landing improperly from a jump and a direct impact collision. Of course, you don’t have to be involved in athletics to suffer a knee injury, but in any case, you should understand the variables of ACL injuries and the possible recommendations for treatment.


The Anatomy of the Knee

The knee is a complex joint composed of bones, ligaments, tendons and other tissue working in unison. The three bones meeting at the knee joint are the femur, or thighbone; the tibia, the shinbone; and the patella, or kneecap, which serves to protect the joint. Bones are connected to other bones by ligaments. The two types of ligaments found in your knee are collateral ligaments, which are found on the outside of your knee and cruciate ligaments that run inside your knee. The ACL runs diagonally across the middle of the knee. A fully intact ACL prevents the tibia from becoming displaced in front of the femur and provides overall stability to the joint.

Signs of an ACL Injury

Many people who suffer an ACL injury report hearing a “popping” noise emanating from their knee at the moment of the trauma. This may or may not be accompanied by a “buckling” of the knee when weight is placed on the joint. Other typical symptoms include:

  • Pain
  • Swelling
  • Loss of range of motion

Medical Diagnosis

In many cases, people ignore knee injuries with the hope the problem will go away on its own. Sometimes that is the case, but it is wise to seek a medical opinion to ensure resuming activity will not cause further harm. A doctor should be able to diagnose an ACL injury by a physical examination of the knee. He or she will compare the injured knee to your other, healthy knee and look for swelling, tenderness and any restrictions in range of motion. As many as fifty percent of ACL injuries are accompanied by damage to other knee components. For this reason, and to determine how badly your ligament is damaged, additional testing such as x-rays or an MRI is often prescribed.

Severity of the Injury

Injured ligaments are often referred to and graded as sprains, although this terminology is a bit counterintuitive. Accordingly:

  • A Grade 1 sprain is where the ACL has been mildly stretched yet continues to function to maintain joint stability.
  • A Grade 2 sprain results when the ACL is stretched beyond the point where it is “loose” and is considered a partial tear.
  • A Grade 3 sprain is where the ligament is completely torn.


The recommended treatment will depend both on the nature of the ACL injury and the activity level, age and overall health of the individual. A torn ACL will not heal on its own, but if the injured person is not very active or is elderly and the joint stability remains viable, rehabilitative therapy may be an answer. For any knee injury, immediate care is important consisting of a combination of rest, elevating your knee as much as practical, applying ice and wearing a brace or compression sleeve when on your feet.

ACL Reconstruction

It is unlikely a torn ACL can be rejoined; the typical protocol calls for surgical removal of the damaged ligament and replacement with a tendon, which is anatomically similar to a ligament. The replacement tendon can come from the patient’s own body or a cadaver and is properly called a graft. The procedure is done arthroscopically, which is less invasive, less painful and offers a quicker healing tie than conventional surgery. Nonetheless, typical recovery to full activity may take eight to12 months.