When Does A Partial ACL Tear Require Surgery?

Male athlete injured his knee on a sports training.
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Question: When Does A Partial ACL Tear Require Surgery?

ACL injuries can either be complete or partial. When there is a partial ACL tear, a difficult decision about surgery needs to be made. An ACL reconstruction involves significant rehabilitation and other operative risks. Deciding when ACL reconstruction is necessary can be a difficult problem, especially when the ACL is only partially torn. So how do we decide when to reconstruct a partially torn ACL?

What is a Partial ACL Tear?

The anterior cruciate ligament is one of the four major ligaments of the knee, and it attaches the thigh bone to the shin bone, the femur to the tibia. It keeps the tibia from sliding too far forward and performs other functions to maintain the stability of the knee during rotation. When a ligament is injured, it is called a sprain. It is most commonly sprained or torn during landing a jump or making a sudden change in running direction, or having a fall.

ACL sprains are graded based on how much the ligament is damaged. A Grade 1 sprain in only minor stretching to the ligament and your knee is still fairly stable. A Grade 2 is a partial ACL tear, with the ligament stretched so much that it is loose and damaged. These are relatively rare. Meanwhile, in the more common Grade 3 sprain, there is a complete tear of the ACL, with the knee joint becoming unstable and surgery almost inevitable if it is to be corrected.

When is Reconstruction Surgery Needed with a Partial ACL Tear?

Treatment of an ACL tear is most dependent on how much knee instability is caused by the injury. Therefore, there is no critical cutoff; they don't decide based on a percentage of ACL fibers torn for determining when surgery is necessary.

The decision is usually based on a combination of symptoms and physical examination findings. If you feel knee instability and have episodes of feeling the knee giving way, that can be a determining factor. The doctor will also consider the tests done in the physical exam, which often include the Lachman test and pivot-shift test. If these are consistent with laxity of the ACL, then reconstruction is a reasonable option.

Unfortunately, incomplete tears of the ACL are difficult to assess. When looking at an injured ACL during an arthroscopy, your surgeon can assess the look and feel of the ligament to make a judgment on the extent of the injury. However, this look and feel method of assessing an ACL is very subjective. Not everyone will agree on what looks good and what looks bad. The better method of assessing a partial ACL injury is based on the aforementioned symptoms and examination findings.

If non-surgical treatment is preferred, you will likely be given a brace and crutches to protect your knee.

Physical therapy for rehabilitation will be started once the swelling goes down.

Surgical Treatment Options for ACL Tears: Learn about the options for the types of grafts used in ACL reconstruction, the timing of surgery and rehabilitation.


Anterior Cruciate Ligament (ACL) Injuries, American Orthopaedic Society for Sports Medicine, March, 2014.

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