ACL Injury Overview

While there are four main ligaments located in the knee, injuries to the ACL (anterior cruciate ligament) are the most common knee injuries seen by Dr. Peter Millett.

The ACL is critical to knee stability, strength and mobility, and is generally injured when the knee is sharply twisted or extended beyond its normal range of motion.  People who experience an anterior cruciate ligament tear often complain of the following symptoms:

  • A popping sound that comes from inside the knee
  • A feeling that the knee is giving away
  • Immediate, intense knee pain
  • Immediate swelling, inflammation, redness and slight bruising

Trauma to the ACL is typically caused during an athletic activity (such as soccer or football) and is also commonly seen during outdoor play (such as water and snow skiing) and from falls and other traumatic accidents. Females are at a higher risk for experiencing an ACL injury—in fact—competitive female soccer and basketball players have 3-5 times higher risk of an ACL injury than their male counterparts.  Strength, size and hormonal changes are notable factors.

Have you sustained an ACL injury?

There are two ways to initiate a consultation with Dr. Millett:

You can provide current X-rays and/or MRIs for a clinical case review ($250).

You can schedule an office consultation with Dr. Millett.

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ACL Injury Grading System

Not all ACL injuries will require surgical intervention. It depends on the grade of the ACL injury. Dr. Millett will perform a Pivot Shift Test to pinpoint how much of the tibia moves in relation to the femur. Pain, swelling, and muscle spasms in the early stages of an ACL injury may make it difficult to determine how much instability is occurring.  So, rather than performing a manual test, Dr. Millett may also use an arthrometer (a machine that measures joint looseness in the knee) along with an X-ray or MRI.

An ACL knee injury typically is diagnosed in ranges from mild to severe:

  • Grade I – A Grade 1 ACL knee injury will include some moderate trauma to the ligament—meaning that some of the fibers are stretched leading to a sprain.  There will be some pain and swelling, but this injury can heal on its own through rest, the use of ice and anti-inflammatory medications and therapeutic knee exercises.
  • Grade II – A Grade 2 ACL knee injury will include some tears to the knee fibers.  Symptoms will be more severe.  This injury is commonly referred to as an ACL ‘partial tear’ and will sometimes require surgery.
  • Grade III – A Grade 3 ACL knee injury is the most severe ACL injury and represents a complete anterior cruciate ligament tear whereas the fibers of the knee ligament are completely torn in half.  Almost always, this particular ACL knee injury will require surgery to fix.

Anterior Cruciate Ligament Tear Treatment


If a person has injured their ACL and they do not experience knee instability nor have the need to use their ACL for sports or other daily activities, physical therapy may be enough to heal the injury. Dr. Millett will look at how old the knee injury is, how old the patient is and the types of activities the patient enjoys.

The common recommendation for immediate treatment of an ACL injury is the well-known rule of RICE:

R:  Rest the knee by using crutches and keeping weight off of it

I:  Ice the knee

C:  Compress the knee with a wrap

E:  Elevate the leg


If more than one ligament in the knee has been torn, or if the ACL tear is a full tear and there are signs of ongoing knee instability, pain and swelling, ACL surgery may be recommended.  In most cases, if the individual is active and participating in sports with a pivoting nature (such as soccer, tennis, skiing or football) surgery will repair the injury so that the athlete can play his or her sport again.  In these instances, ACL reconstructive surgery is the best option.

An ACL reconstruction is a surgical procedure—almost always performed arthroscopically with one or two incisions—that involves removing fragments of the damaged ACL and replacing it with another form of soft tissue, called a graft.  Dr. Millett will usually prefer to use a patient’s own tissue for the graft. The patient’s own tissue heals faster and reduces other known risks. In patients who are older or who have had prior knee injuries and who may not have sufficient tissue for grafting, an allograft might be a better choice. An allograft uses tissue donated by an individual at the time of death.

There are many types of devices used to secure the graft to the bone. Some examples are interference screws, screw/ washer, endobutton, and cross pins. Some are metallic and others are absorbed by the body over time. The type of graft procedure the surgeon chooses will determine the fixation technique.

ACL reconstruction can either be performed in an out-patient setting, or as an in-patient procedure with an overnight hospital stay.

For additional resources on an ACL injury, or to determine the severity of your anterior cruciate ligament tear, please contact the orthopedic office of Dr. Peter Millett.

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