Knee Ligament Injuries: Tears of the Anterior Cruciate Ligament (ACL)




Overview of ACL Tears

Perhaps the most important ligament in the knee is the anterior cruciate ligament (ACL). The ACL is no bigger than your little finger and runs from the front of the tibia (shin bone) to the back of the femur (thigh bone). It provides stability to the knee when twisting or turning and prevents the tibia from moving forward relative to the femur. This ligament is crucial to activities that require quick cutting and pivoting.

There are three degrees of ACL sprains. In a first-degree sprain, the ligament fibers are stretched but not torn. In a second-degree sprain, some of the fibers are torn but others remain intact. In a third-degree sprain, all of the ligament fibers are torn, resulting in an ACL-deficient and inherently unstable knee.

Signs of an ACL tear

In either mechanism of injury, patients often hear or feel a “snap” or “pop” in their knee. The knee immediately begins to swell and becomes painful, and patients often have difficulty walking without assistance. As time passes, the initial pain and inflammation subside and patients may complain of persistent knee instability. This is especially apparent when they try to run or pivot on the knee.

It is not uncommon to damage other structures in the knee with the initial ACL injury. This includes disruption of other ligaments, tendons, and/or cartilage of the knee. These other injuries can result in more pain and increased swelling and complicate the diagnosis and treatment.

Mechanism of injury

There are two common ways that the ACL is injured. In the first situation, the individual may be running and quickly cut or pivot. This results in excessive stress and subsequent sprain of the ligament. The second scenario involves someone or something falling onto the knee while it is fixed in place. This excessive amount of force results in a strain on the ligament.

How is an ACL tear diagnosed?

In order to determine the cause of your symptoms and the extent of the injury, your specialist will ask you questions and perform a physical examination. X-rays are helpful in viewing the bony anatomy of the knee and can confirm or eliminate a diagnosis. After your specialist has conducted the examination, he or she may recommend that you undergo more diagnostic tests such as an MRI (magnetic resonance imaging) scan. An MRI allows your specialist to clearly see the muscles, tendons, and ligaments of the knee. This information helps him or her formulate a treatment plan tailored to your needs.


What are my treatment options?

The decision to proceed with surgical versus nonsurgical treatment is determined by the patient’s overall health and physical activity. There is a consensus among orthopedic surgeons that in a physically active patient a torn ACL requires surgical reconstruction. Without an ACL, the knee is inherently unstable and the patient risks further injury when participating in activities.

Immediately after injury, the treatment plan is focused on reducing the patient’s pain and swelling while increasing knee strength. Physical therapy can be very useful in this regard, and your specialist may wish that you see a physical therapist prior to surgery. If this is the case, surgery can be scheduled once the pain and inflammation are under control.

ACL reconstruction is performed arthroscopically to ensure proper graft placement and minimize the risk of complications. The old torn ligament is removed and replaced with a new graft harvested from one of several sources. An autograft is when the new ligament is harvested directly from the patient’s own patellar or hamstring tendon. An allograft is harvested from an outside source, most commonly a cadaver. The selection of the graft source depends on the patient and what the surgeon feels will give the most successful outcome.

Recovery after ACL surgery

After surgery, you can expect to be in a brace for up to a month. Approximately one week after surgery, you will see your specialist and begin physical therapy. The goal of these sessions is to decrease the postoperative pain and swelling while increasing your strength and range of motion. As your knee starts to feel better and the graft begins to strengthen, your specialist and physical therapist will clear you for increased activity. Additionally, a brace may be prescribed for you to wear during athletic activities.

Your specialist may prescribe a cold compression therapy unit for you to use postoperatively (Aircast Cryo/Cuff). Integrated cold and compression is clinically proven to reduce postoperative swelling and pain, and help you regain range of motion. Summit Orthopedics believes that the cold compression therapy unit will provide you with the best possible outcome in the days following your surgery.

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