All About ACL Injuries

By Dr. Katy Morris

If I had a dollar — scratch that, just a dime — for every time I have heard a patient, a friend, or some random person my mother gave my number to say, “So-and-So said I tore my ACL. Please tell me it’s not my ACL!” all my medical school loans would be paid off by now.

The anterior cruciate ligament, or ACL, sure gets a lot of attention, but most people have little or no idea what it is, how it’s injured, or how to treat it. Worst of all, most people don’t realize that women are two to eight times more likely to tear this ligament than men!

What is the ACL and how is it injured?

The ACL, is one of four ligaments connecting the bones of the knee together. It is centered in the middle of the knee, behind the kneecap. The knee joint acts like a hinge. It has some involvement in side-to-side movement and rotation, but the ACL primarily exists to prevent and protect our knees from the extremes of these movements. It provides a significant amount of stability so that we can do more than just run in a straight line. The ACL makes jumping, pivoting, turning, and spinning possible.

Most people might imagine two soccer players colliding or a football player getting tackled when they think of ACL injuries, when on the contrary, often all that’s needed to cause a tear to this ligament is slowing down and changing directions. In fact, nearly 70 percent of ACL injuries are noncontact injury. It can happen during a plyometric workout, jumping down from a pull-up bar, getting a ski caught in the snow or even during a co-ed kickball homerun celebration (don’t ask) — and those are just a few scenarios.

What are the risk factors for tearing the ACL?

There is a lot of research dedicated to testing theories and ideas related to ACL injury risk factors, and for this article I will divide the findings into two categories: external factors (outside our bodies) and internal factors (within our bodies).

The proven external factors, for men and women — that is, factors that we can technically change or avoid — include:

  1. Artificial flooring or turf (instead of natural hard floors)
  2. Number or type of cleats
  3. Dry outdoor climates

The internal risk factors are what put women at an increased risk of a tear.

The proven internal risk factors — that is, structural aspects of our bodies that we can’t change — include:

  1. Q angle: a measurement from hip to knee (Figure 01)
  2. Variations in the anatomy of the bones that make up the knee, the femur and tibia.

The proven internal risk factors that we can change:

  1. The way we jump or land, all the time or after fatigue sets in. See the following three videos for examples:
    • Video 1: Male vs Female Typical Landing Pattern
    • Video 2: Side by Side Jump
    • Video 3: Female Original and Corrected Landing)
  2. Neuromuscular control and reactions, specifically the ratio of the strength of and contractions in the muscle groups of our legs (quadriceps and hamstrings)

One thing that has yet to be proven is whether or not the menstrual cycle and female hormones play any role. 1,2,3 Some experts say yes, some say no. Although theories abound, reliable research is hard to produce. There are too many variables in our bodies and lives that make it difficult to link one specific thing, like our cyclic estrogen and progesterone levels, to why we, as women, tear ACLs at a higher rate.

What can you do to prevent an ACL tear?

Many studies have shown that females placed in a preventive or corrective exercise program greatly decrease their risk of tearing an ACL when compared to women following a training program without preventive or corrective elements. In some studies, the decrease was as much as 75 percent! 4,5,6,7

Programs like the ones in these studies emphasize improving strength, balance, plyometrics, and agility exercises with regular warm-ups and cool-downs. The main focus of correction in these programs has been the “knee over toe” position when cutting and landing while keeping the knees and hips in a flexed position. Results can usually be observed after six to eight weeks of consistently performing the corrective exercises for 15 minutes a day, three days a week. A refresher course now and then seems to help, too!

Variations of these programs are readily available, and many trainers, coaches, and active females implement them into their routines. 8,9,10

How are ACL tears treated?

I may be a surgeon, but contrary to popular belief about surgeons, I love preventing surgeries! I love taking care of active people. That’s why educating women on ways to avoid ACL tears and other injuries is so important to me. However, if I didn’t mention ACL treatment, surgery, and recovery, it would leave some folks with a lot of questions.

Rather than diving into the nerdy details of ACL repair surgery, instead I am going to clarify why most ACL tears end up on the operating table, explain some of my decisions as a surgeon (usually based on the individual patient), and provide a few key points on recovery and rehabilitation after the surgery.

Some of the most common questions I get are:

  • Do ACLs repair themselves after a tear? Short answer: No
  • Do ACL tears have to be operated on? Short answer: No.
  • Should ACL tears be operated on? Short answer: It depends.

Now, the long answers.

An ACL is not a heart attack or a brain tumor. Having ACL surgery will not literally save your life. The treatment is about quality of life, and a lot of things have to be considered. It helps to make a pros and cons list.

The ACL does not have a good blood supply, so it can’t receive essential nutrients for optimal healing from the blood that would repair and heal the tear.

When I said that an ACL helps with stability of the knee, it’s not just so that we can stay active and keep moving our bodies. The ACL also prevents stress on other structural elements within the knee, like the cartilage.

The most basic definition of arthritis is loss of cartilage. It has been proven, over and over again, that a knee without an ACL will develop arthritis much faster than a knee with an ACL.11 The arthritis can show up as soon as a couple years after a tear.

The same thing is true of a meniscus tear. Tearing an ACL puts more stress on these structures, and that added stress causes them to wear out more quickly. Arthritis and meniscus tears can hurt, with activity or all the time. So, even if you don’t jump, skip, pivot or dance, getting an ACL tear treated with surgery can possibly prevent pain in the future.

With all that said, this is real life we are talking about here.

  1. What if you are not ‘super-active’?
  2. What if you already have arthritis?
  3. What if you are scared to death of surgery?
  4. Do you have a medical condition that might make surgery unsafe?
  5. Are you unable to have surgery because you could lose your job, or because you are the primary or sole caretaker of a child or a aging loved one?

These are all very important things to consider. This is why I say no or it depends when asked whether you should have surgery.

Recovery and rehabilitation are a lot more straightforward! Some of the steps overlap, especially in the beginning, but most surgeons follow the same plan with just a few personal touches. This plan typically moves through the following phases:

  1. Recover from the actual surgery, managing pain, swelling, and incision healing.
  2. Get full range of motion back.
  3. Start building muscles back up. (emphasis placed on quad)
  4. Gradually increase in-line activity (elliptical, jogging).
  5. Start and gradually progress exercises that will stress the new ACL (plyometrics, pivoting, jumping, shuffling)
  6. Start sport-specific training.

On average it takes about nine months after surgery to return to full activity without any restrictions. The range is six to 12 months. This might sound like a long time, but ACL surgery gives you a new ACL so it takes time to fully heal. You can’t safely stress that new ACL until it’s ready to accept that stress. Sure, you can build muscles that stabilize the knee, you can start in-line running, but the other stuff will need to wait until the ACL is completely healed. The hardest part for most ACL surgery patients is that the knee often feels amazing long before it has completely healed, making it hard (but not impossible!) to resist the urge to try activities that are deemed unsafe before the knee is ready. Sadly, some people figure this out the hard way, by re-tearing the new ACL.

This may feel like information overload, all for one little knee ligament, but it is for good reason. The ACL is responsible for so much, and women are more likely to tear it! Though we’re still learning a lot about the ACL, knowing the risk factors that you can control and being aware of ways to protect yourself from an ACL tear is valuable knowledge that can help you optimize your quality of life.

Coaches’ Corner

Coaches and trainers can be incredibly helpful not only as a first line of defense when it comes to reducing the risk of ACL injuries, but also in ensuring the client gets a proper diagnosis and treatment from a medical professional.

Risk Reduction

The Santa Monica Sports Medicine Foundation offers an outline of a program that has been shown to decrease the risk of ACL tears in females. Little to no equipment is required, it can be performed in many different environments.

Identifying An ACL Tear

While diagnosing is best left to a medical professional, as a coach or trainer it’s important to know the signs of a torn ACL in order to help your client or athlete get immediate and optimal care. Things to listen and look for if you suspect a torn ACL:

  1. Did they feel a pop?
  2. Is there pain deep in the knee?
  3. Was there immediate swelling? (This happens 70 percent of the time.)
  4. Are they avoiding fully straightening the knee?

If you suspect an ACL tear, the two most important things to do are discontinue all activity and strongly recommend scheduling an appointment to see a doctor right away.


After your athlete or client has been diagnosed and treated by a physician for an ACL tear, your help and influence can make a huge difference. An ACL tear and treatment (surgery or no surgery) can have major psychological effects. Keeping the conversation open and encouraging compliance with the rehabilitation plans helps immensely! You’ve already gained their trust, so your advice and support go a long way.

Your client will most likely still be able to do isolated upper body workouts and certain lower body and core workouts early on in the rehabilitation process. Most surgeons prescribe regimens that can be done outside of formal physical therapy to help in the rehabilitation process. Having a trusted, educated trainer who can help them maintain their fitness and prevent significant loss during this process is an added benefit.

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About the author:  Dr. Katy Morris

Katy Morris is a sports-trained orthopedic surgeon. Her focus is on treating individuals of all ages who participate in both traditional and alternative sports and activities. She dedicates time both in and out of her office to the all-around injury prevention and treatment of the active woman athlete. When she isn’t treating patients, Katy is the active woman athlete. She is an avid snowboarder, rock climber, and hiker. She also enjoys a daily yoga practice, strength training and occasional surf. If you have a question, you can reach Katy via email at [email protected].


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  8. Bien DP. Rationale and implementation of anterior cruciate ligament injury prevention warm-up programs in female athletes. J Strength Cond Res 2011; 25(1):271-285.
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  10. Pep Program, Santa Monica Sports Medicine Research Foundation.
  11. Lohmander LS, Englund PM, Dahl LL, Roos EM. The Long-term Consequence of Anterior Cruciate Ligament and Meniscus Injuries. Am J Sports Med 2007; 35 (10):1756-69.

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