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Torn ACL Q&A

August 14, 2018

What is the ACL?

The ACL, short for “Anterior Cruciate Ligament,” is a ligament in the center of your knee that helps add to the stability of your knee.  It keeps your tibia (shin bone) from sliding forward on your femur (thigh bone), and also provides stability from the two bones “twisting” on one another. 




Itact ACL, Torn ACL

Reconstructed ACL

How does someone tear their ACL?

The ACL can be torn in many different situations: car accidents, sports events, or even just simple twisting injuries.  As physicians, we designate between “contact” and “non-contact” ACL injuries.  Contact injuries occur due to a direct blow to the knee (car accident, tackle, kick).  Non-contact injuries happen due to a twisting injury, often when an athletes plants their affected knee and pivots the opposite way.  

How do I know my ACL is torn?

The ACL can be torn in many different situations. Sometimes, patients can report that they felt a pop or something “give way” in their knee, however, this does not happen in every situation. Usually, the knee is painful and swells after the injury.  Oftentimes, people ARE able to walk and bear weight after an initial period of rest.  The knee often feels unstable, or “wobbly.”  Sometimes, an ACL injury is associated with injuries to other structures in the knee (meniscus, other ligaments, cartilage injuries).  If you have a knee injury with significant swelling, you should see a medical professional who can clinically test your knee for ACL stability.  If there is any suspicion for an ACL tear, an MRI will provide a definitive diagnosis.

Who is "at risk" for tearing their ACL?

Typically, we think of athletes being at risk of ACL injuries, but ANYONE can tear their ACL, regardless of activity level.   Women are thought to have a higher incidence of “non-contact” ACL injuries, due to the way that they are built, hormones, and the way that their muscles fire and the way that they move.

Do you have to have your ACL reconstructed?

The main reason to reconstruct an ACL is to restore the stability of the knee to protect against further injuries to your meniscus or cartilage.  If you are an older individual with developing arthritis in your knee, it may NOT be beneficial to have your ACL reconstructed.  However, we do recommend that young or active individuals without knee arthritis have their ACL reconstructed, because we think that restoring stability to the knee can protect the meniscus and cartilage in the future.

What are some important things you would recommend I discuss with my surgeon prior to having an ACL reconstruction?

  • Do I need to do any rehabilitation to optimize my results BEFORE surgery?

  • Do I have a meniscus injury, if so, will you repair it or will you trim the meniscus out?

  • What will my rehabilitation be after the surgery, how often and for how long will I need to do rehab?

  • What type of graft (tissue) will you use to reconstruct my ACL and why?

  • When can I return to work/sports or other specific activities?

  • What are the risks of surgery?   How likely are these risks to occur?

  • What can I do to prevent re-injury to my new ACL or injury to the other knee?

What exactly do you do when you operate on the ACL?

ACL Reconstruction surgery is a BIG DEAL! We operate through small incisions, but we do a LOT of work inside the knee.  You can expect to have pain after surgery, as it is surgery!  The point of an ACL reconstruction is to recreate a new ACL in the exact same anatomic position as your old ACL.  Surgery consists of taking tissue from either a cadaver or from another part of your body, drilling tunnels (8-10mm in diameter!) in the femur and the tibia bone, and placing the graft in those holes, fixing them with either sutures, buttons, or screws.  The placement of these tunnels in an “anatomic” position is very important to the function of your graft.   The fixation of the graft provides temporary attachment of the new graft to the bone until your body can “accept” the graft as its own and grows into it.  The ultimate strength of the graft comes from soft tissue graft healing to the bone tunnels and incorporation of the graft into the body as your “own” tissue.  This incorporation process takes several months to complete. 

What are the different options for graft types for an ACL reconstruction?

  • Autograft (Graft obtained from your own body, from a different location)

    • Bone-Patellar Tendon-Bone (BTB)

    • Hamstring

    • Quadriceps Tendon

  •  Allograft: Tissue obtained from a cadaver (deceased donor tissue)

What are the pros and cons of different graft types? And how do I know which one to choose?

Typically, I do not recommend Allograft tissue in younger patients (<25 years old), as these are more likely to fail/re-tear in a young, active person.   All three autograft tissues are good options, and all have pro’s and con’s.  Personally, I am a HUGE advocate of the quadriceps tendon autograft, and it would be the graft that I would choose for myself should I tear my own ACL.   I believe that it is a great graft with predictable length, width, and structural properties without the morbidity of a BTB autograft, and is an all-together better choice than a hamstring autograft if choosing between soft-tissue grafts. I recommend having a discussion with your surgeon regarding which graft they are most comfortable using and weighing the risks and benefits of each graft.    

Below is a list of “Pros and Cons” of different graft types that I provide to my patients.

Tissue can be used from many different places to re-create your ACL.   These are the most commonly used places to get tissue for your new ACL. 

Allograft: tissue obtained from a cadaver

  • Benefits: no donor site morbidity, may have an easier recovery with less pain

  • Downsides:  Very small risk of disease transmission that is approximately 1:8,000,000. Slightly higher risk of graft rejection or re-tear with a cadaver graft, especially in younger patients 

Autograft: tissue obtained from yourself

  • Bone-tendon-bone, “BTB” (Patella Tendon):
    • Benefits: Bone to bone healing, “gold standard”

    • Downsides: Frontal knee pain, patellar tendon rupture, infrapatellar tendon contracture, patella fracture, tendon too long for the knee, large incision, numbness on front of knee, stiffness/cyclops lesion

  • Hamstring Tendon:

    • Benefits: Small incision, high-quality graft

    • Downsides: Unpredictable graft size (diameter) which may lead to increased risk of failure, no bone to bone healing, hamstring weakness (5-10% strength), numbness around harvest site, stiffness/cyclops lesion

  • Quadriceps Tendon:

    • Benefits: Predictable graft size, small incision, good outcomes, fills tunnel footprint

    • Downsides: no bone to bone healing, hematoma formation at harvest site, rectus muscle retraction if graft harvested into muscle, stiffness/cyclops lesion.

Will I be able to get back to sports and other activities I like to do after an ACL reconstruction? And how long will it take me?

ACL surgery is a BIG DEAL!  It is a very prolonged and labor intensive recovery.  If you are an athlete, you can expect to return to your sport in approximately 1 year, however, it may take longer.   I do not let my athletes return fully to their sport for 12 months, as this is the length of time that it takes your graft to heal and to regain enough strength and muscle control to protect the new ACL from re-injury.  However, if you are not diligent with your rehabilitation, this may take longer. Also, there are some studies that show that mental/psychological readiness to return to sport is just as important, so you have to believe that you are ready as well!

How important is physical therapy after an ACL reconstruction? Should I go to physical therapy before my surgery?

I believe that physical therapy BEFORE ACL surgery is very important.   The purpose of “ACL Pre-hab” is to restore your range of motion of your knee to prevent stiffness, and to strengthen your quadriceps muscle, which likes to shut-down and become weak after knee injuries.  Your physical therapist should also work on balance (proprioception), as this is an important factor to recovery.  We know that if we operate on patients who have not obtained their full range of motion and quadriceps strength, they have a high likelihood of stiffness and poor outcome after surgery.

I tell all of my patients that ACL surgery is 90% about your recovery after surgery.  As a surgeon, I get to spend 2 hours working on your ACL and reconstructing it.  However, the patient has to spend 1 YEAR with a physical therapist (1-2 times per week), and work daily on rehab exercises before you are able to return to therapy.  Failure to go to physical therapy often results in stiffness of the knee, inability to return to walking/running normally, weakness, and pain.  

Will I be at higher risk of re-tearing my ACL, or tearing my ACL in the other knee, when I return to play?

If you have not done proper rehab and your surrounding muscles are weak, or are not firing in the correct sequence, you can be at risk of re-tearing your ACL.  Often, people who tear the ACL’s have poor body mechanics to begin with, and if this is not corrected, you will be at higher risk of re-injury or tear of your other ACL.   This is why rehabilitation and good physical therapy are so important.   It takes 9-12 months to recover, strengthen, and be ready to return to play after ACL surgery, and the rehabilitation is one of the most important aspects of your recovery.  

Can I decrease my risk of tearing my ACL? If so, how?  

Working with a physical therapist to improve your strength, range of motion, body mechanics, and proprioception (balance), will all help you decrease your risk.  Working on jumping and landing mechanics are also important.  There is some new research that you can even train your visual input system (eyes) to help with muscle firing patterns to decrease your risk!  


The physical therapists at Specialized Physical Therapy, recommend some great exercises to decrease your risk of ACL injury.  Check out next week to find out what they are!


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