Partial Anterior Cruciate Ligament Injuries – Partial ACL Tears

Author: Howard J. Luks, MD- Posted in: ACL, Knee, Sports Medicine 39 Comments

Why do Partial ACL injuries occur?

Injuries to the ACL or Anterior Cruciate Ligament are becoming more and more common.  The normal ACL is made up of  two pieces, or bundles.   If you injure only one of the bundles then you have a partial ACL tear, as opposed to a complete ACL tear.  First we will explore what a partial ACL tear, then we’ll explore how partial ACL tears are treated.  

What is the Anterior Cruciate Ligament

The anterior cruciate ligament  – ACL –is one of the more vital and more commonly injured ligaments within our knee. Ligaments are generally small, but very tough structures which hold our bones together.  The ACL allows us to twist, pivot and rapidly accelerate and decelerate.  Most partial ACL injuries are non-contact in nature.  With a partial ACL injury or complete ACL injury your knee might feel unstable with those same activities.   Partial Anterior Cruciate Ligament Tear Injury

Partial ACL Tear

ACL Tear





If you sustain a pivoting or twisting injury and feel a pop — there is a strong chance the you injured your ACL.  Most people who have a partial or complete ACL tear will then notice significant swelling shortly after the injury.  

The anterior cruciate ligament or ACL is the most commonly injured of the four major ligaments that exist within our knee. Most patients who have sustained an injury to their ACL will have enough discomfort that they will seek attention either in an emergency room or in orthopedists’ office fairly rapidly. Whether or not an ACL tear exists can be determined by a good physical exam.  An MRI can be useful to confirm if a partial ACL tear or a complete ACL tear exists.  The MRI will also show if any other structures in the knee were injured.  


Complete ACL Tears:

A complete ACL tear involves the complete disruption of all of the ACL tissue that connected both the femur and tibia. You may simply possess discomfort, pain and swelling – – – or you may perceive that the knee is unstable and feels like it wants to buckle or give way. We have covered the treatment of complete ACL tears elsewhere within this website,  and whether or not ACL surgery is always necessary. 

For the recently injured, or those in the preparation phase for surgery I recently placed two ACL Surgery blog posts on this site.

Partial ACL Tears: Stable versus Unstable

A partial ACL tear involves an injury to only a portion of the ACL, or one of the bundles.  Some partial ACL tears leave you with a stable, functional knee, and some partial tears will result in an unstable knee.  With some partial ACL tears,  the knee might feel like a knee with a complete ACL tear.  Some patients who have a partial ACL tear will be able to return to their prior level of activity without complaints of buckling,  instability or giving way. Unfortunately, a fair number of you will not be able to return to your prior level of activity because your knee feels unstable or loose.

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partial ACL tear Howard Luks Westchester County, NY



What I’m getting at is simply the fact that we should  not look at your ACL  tear as being “partial” or “complete”, we look at your KNEE as being  “stable” or “unstable”.  If you have a stable partial tear of your ACL, that means that you have torn a certain portion of your ACL fibers, however, you are still able to participate in sports without the feeling of the knee giving way or being unstable. On the other hand, If you possess an unstable partial tear of your ACL, that means that you have torn enough of your ACL fibers that your knee no longer feels stable. That means that you are at risk of further injury if you return to your prior level of sports participation. Furthermore, every time your knee buckles or gives way you run the risk of tearing other structures within the knee, such as the medial or lateral meniscus. If you sustain tears of either the medial or lateral meniscus, which are the shock absorbers within the knee, then you are at risk of developing osteoarthritis. You therefore want to eliminate or minimize the risk of buckling,  instability or giving way.   If you present with a partial ACL tear and complaints of instability we will likely talk about the possibility of undergoing an ACL reconstruction or possibly an ACL augmentation.

Partial ACL tear treatment options: If surgery is necessary:

The difference between an ACL reconstruction and an ACL augmentation is fairly simple. During the process of an ACL reconstruction we will reconstruct or replace the entire ruptured ligament. Anatomically, the ACL is composed of two separate bundles and a complete reconstruction will compensate for both of those bundles. In an ACL augmentation, you have only sustained a partial tear. That means that a portion of your ACL remains intact and might be normal. Many high volume ACL sports medicine orthopedic surgeons are capable of reconstructing only the torn portion of the partial ACL tear. This leaves the normal portion of the ACL alone. There are many advantages to an ACL partial tear augmentation over a full ACL reconstruction. While the discomfort, and the nature of the surgery is virtually identical – – – it is far more likely that someone who undergoes an augmentation will have a much more natural feeling knee when all is said and done. The reason for that is because the normal ACL has certain nerves within it. Those nerves give the brain certain feedback as to the position of the knee joint. It turns out that those nerve fibers are quite important. If we preserve the intact portion of your ACL, then we are preserving those nerve fibers and hopefully preserving the integrity of your knee in the long run.

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Howard Luks MD, 19 Bradhurst Avenue, Hawthorne, New York 10532, United States - Phone: 914-789-2735 Email:

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39 Responses to “Partial Anterior Cruciate Ligament Injuries – Partial ACL Tears”

  1. Reply Anterior Cruciate Ligament Tears: Decision Making For Derrick Rose says:

    [...] that leads to the feeling of instability.   Derrick Rose has a complete ACL tear… but partial tears of the ACL occur fairly often.  Sometimes enough of the ligament remain that you will not experience [...]

  2. Reply Name Joe G says:

    Dr. Luks,

    I just received word that I have a partially torn ACL and partially torn meniscus. I am 57 yuears old and the injury was sustatined while I was officiating a high school football game. My doctor has offered two routes: 1. a “clean-up procedure” without ACL reconstruction. I would have to wear knee brace when officiating in the future but without ACL surgery, my ability to cut, move sideways will be limited, or 2. ACL reconstructive surgery and meniscus procedure. This should give me near pre-injury movement and running abilities.

    I’m torn and confused; I would like to officiate 5-8 additional years. I do have a CD copy of the MRI and the x-rays were negative regarding fractures. Thank you. Excellent website and very informative!

    • Reply Howard J. Luks, MD says:

      I’m left wondering why one of the options discussed wasn’t physical therapy? Many people with partial ACL tears have a functional ligament and no instability. A few people will have instability with a partial tear and then a decision can be made with regards to bracing or surgery. Undergoing an ACL recon at 57 is not going to be a simple straightforward process. Also, keep in mind.. Many active 50 somethings have meniscus tears and do not even know it. Not all meniscal tears require surgery.. Even in active individuals.

      Let me know how the PT works for you.
      Howard Luks

  3. Reply Adam says:

    Dr. Luks

    I’m a 28yr old male that was diagnosed with a partial ACL tear in my right knee. I am still very active lifting weights, playing softball, and basketball on a weekly basis. I’ve been living with it for 4 years. Since the incident “basketball” I’m not nearly as strong lifting or explosive jumping and running and my knee feels tight and weak for days after heavy sports or leg workouts, although it doesn’t buckle. What would be your thoughts on my situation?



    • Reply Howard J. Luks, MD says:

      Adam.. A thorough exam and further discussion is necessary. Instability comes in different “flavors”. Some people will have significant instability where the knee buckles and you fall or it can be more subtle. After a discussion and an exam you and your surgeon can determine if therapy, or surgery is potentially in your best interest.

      Good Luck
      Howard Luks

  4. Reply ACL Surgery - Start to Finish : Part I - Howard J. Luks, MD says:

    […] The ACL is one of the four strongest ligaments in our knee.  It sits in the center and is made of a very tough tissue we call collagen.  The ACL keeps our knee stable for sports involving pivoting, turning and twisting at rapid speeds.  The ACL is actually made up of two pieces or bundles.  Sometimes an injury to your ACL only involves one bundle and we refer to that as a partial ACL tear.  More on partial ACL tears. […]

  5. Reply Jerry john says:

    Doc Luks,,

    i am only 17 years old and in this April 21 2014 it will be 4 years after my ligament tear , I had a very bad time , I seen more than 17 doc. half of them said a surgery is important and some said it will be better if I am having my surgery after am an adult , so that the growth may be complete. ……even though there were times not even my pain killers couldn’t help me… I think it has been 4 months I am feeling much more less pain , and am getting good exercise ….and I can walk with out using any aids …and I am in a doubt that had the ligament tear completely cured…I had been googleing it for some time to know a better result, until I find you,….I seen some results like people talking like the muscle must had grown and such kind of things……doc,” I need to know if I take a MRI scan , is there a chance to show the fully grown ligament, or a cured ligament”……instead of showing the tear and the muscle grown in between them…..I will die to know it from you….because I had seen the surgery in youtube and am seriously very scared…….my presen situation is : much more better in walking , feeling a little more strong leg and tiny curve back words when I normally stand ,but no pain.

    • Reply Howard J. Luks, MD says:

      Jerry… At 17, if ACL surgery was needed, it is safe to proceed from a growth perspective. The ACL ligament does not heal, and muscle does not grow inside the knee to fill the gap after an ACL tear. IF your knee is unstable it is time to sit down once again with a sports medicine doc and talk about your options. Another MRI might shed some light on the situation and let you know if anything else has been injured too.

      No one can force you to have surgery… if it scares you, you might not be ready… or you might simply need to find a doc you are more comfortable with ?????

      Good Luck
      Howard Luks

  6. Reply rachael says:

    i am 34 and I compete in mixed martial arts. I work fulltime as a nurse. I have a partial tear in acl and mcl from jiu jitsu practice in oct. Im 12 weeks out and still cannot fully straighten my leg and I cannot bring foot to butt. My dr keeps telling me to rest it. Its been 3 months. Im way to active and competitive to continue to sit around and “rest”. I live in georgia. Any thoughts?

    • Reply Howard J. Luks, MD says:

      Rachael.. sorry. Combined injuries to the ACL and MCL can hurt quite a bit. MCL injuries in particular are well known for causing a prolonged recovery process as you are experiencing. While I can not comment on your case in particular, at this point an MCL partial injury should be healed enough to allow for physical therapy to assist in gaining back the range of motion.

      If your knee feels unstable, that is something that needs to be addressed with your surgeon. Multi-ligament injuries are notorious for producing very sore, unstable knees.

      Good Luck
      Howard Luks, MD

  7. Reply Sudie says:

    Dr. Luks,

    Back in late November I fell while skiing and hurt my knee. At the time, I was across the country and unable to get an MRI because of insurance reasons. My knee was very swollen, but the pain was not bad at all. About a week after the incident, I returned to the gym and was able to exercise without any serious discomfort in my knee. Eventually I was able to walk without any limping and it seemed like it was going to heal on its own. When I returned home a week ago (about a month after the injury occurred) I got an MRI and the results showed that my ACL is torn at the femoral end and I have moderate bone bruising. I have not consulted with an orthopedic yet, but I do have an appointment in about a week. My question to you is do you think it would be possible to return to my normal, very active lifestyle (mainly skiing and running) without having surgery?


    • Reply Howard J. Luks, MD says:

      That’s a great question Sudie. Unfortunately I can not answer it for you :-(. There are some people who get by without an ACL, but they generally do not participate in aggressive sports such as skiing. Ms Vonn can attest to the fact that it is very hard to ski without an ACL.

      Good Luck with your meeting with your Orthopedist.
      Howard Luks

  8. Reply NameHeshan gunaweera says:

    Dear Doctor Luks,
    I am 44 years old from Galle Sri Lanka. I play badminton since the age of 8 for my school , university and the club.In 2012 August I had left knee injury- lateral collateral ligament tear at its insertion to the femoral condyle, anterior cruciate ligament tear (Report has not mentioned whether it is a 100% tear or not) and tears in of posterior horns of both menisci and meniscal cyst in relation to lateral condyle (M.R.I report- 2013/11- got late due to technical reason) while playing badminton.I had pain, mild swelling and restricted movements initially but with physiotherapy and anti inflammatory drugs now I can walk fast and climb stairs (with mild weakness) without pain and discomfort . I notice some muscle wasting in my left thigh. I did not attempt running or playing badminton, but now I enjoy swimming without painful knees.I do not intend to play badminton.
    Can you please tell me , Dr Luks
    1. the suitable mode of treatment considering the future course of my life.
    2. I f it is not reconstruction of A.C.L. what is the likelyhood of osteoarthitis in my knee.
    3.the sport activities and exercises suitable for me to avoid muscle wasting further and keep me fit.

    • Reply Howard J. Luks, MD says:

      With a multi-ligament injury – the ACL and LCL – you are at very high risk of having significant instability and giving way. If that happens then you can suffer other injuries such as meniscus tears or damage to the cartilage.
      Unfortunately with a multi-ligament injury and a meniscus tear, you are at an elevated risk for developing arthritis. Weight training under supervision in a gym would likely be well tolerated. But any sports would be not be advisable given the unstable nature of your knee.

      Good Luck
      Howard Luks

  9. Reply emrah says:

    Dear dr.lucks
    i fell on my leg while playing soccer 3weeks ago. My i have a partial acl tear. Doctor took away my meniscus. Since the operation i have been takin phsical treatment everday. Now my knee stabilty is getting well gradually and i can walk. What should i do to recover fullly. İ afraid of using my leg in case i can hurt my acl totally. İs it possible to tear it totally while trying to streghten my leg and what exercises should i do to streghten my leg.need your help, thank in advance

  10. Reply David Rodriguez says:

    Hello, I am 18 years old and I was playing basketball and when I jumped up for the rebound I felt shakingon my knee than I went to the ground and was unable to stretch my leg. After 20 seconds I slowly stretched it out and it felt like something poped into place. I did not hear a pop though. Its been a month exactly that I have had this injury. I went to an orthopedic doctor a few days ago and got my MRI done and I woll find out exactly what I have in 1 week. My orthopedic doctor thinks it may be a parcial acl teae after some movements with my leg. I have been able to walk fine with and without a brace. However , yesterday while walking I was not paying attention and my leg locked and leaned back and I got pain for about 30 seconds. I dont mot feel pain though on the acl. My injury is on my left leg and on the left side of my knee. I truly hope I didnt do more damage to any of the ligaments and am placing ice on it every day to ensure I do not injure it. My legs do not lock up. I dont even feel pain when I walk. The only time I ever feel pain is if my leg straightens and I put weight when it leans back. Please respond. Im a kid whos freaking out that he may never be able to play basketball again. What do you think it might be? And what type of surgury would you recommend? Iv been told of many types of way but is it really good to take a piece of your hamstring out to heal your ACL? I would love some feedback. Thankyou

    • Reply Howard J. Luks, MD says:

      David.. I’m sorry that I’m not going to be able to be of great assistance to you tonight. Too little information.. and I can’t offer treatment recommendations to people online who are not patients of mine. Given the injury that you note, it MIGHT not be an ACL issue, but MIGHT be a bucket handle meniscus tear. That would explain the locking you experienced. Time will tell young man… let’s see what the MRI shows. Feel free to come back after you have some more information. Please understand that this is for informational purposes only.. it is not meant as a diagnosis or treatment recommendation. To avoid further injury you can talk to your surgeon about whether or not crutches would be useful to prevent further injury, until you know the results and have a plan in place.
      Good Luck
      Howard Luks

  11. Reply David Rodriguez says:

    I do apoligize for the questions. I didnt notice until I reached the bottom of the page, thankyou for the input though! The doctor however told me not to use crutches. He didnt really get much into detail. But I figure he knows best.

  12. Reply Luke says:

    Hi Dr. Luks,

    I recently got my MRI results and they showed a high grade partial ACL tear, Grade II MCL tear, and a small medial meniscus tear. I am young but do not regularly play sports. My doctor has said to wait it out for 4 months using physiotherapy and assess from there if surgery is needed. It feels fairly stable to me. Usually what is done in these situations because the ACL is combined with MCL and meniscus? I am going with my Doctors advice but just curious on what is usually done.


    • Reply Howard J. Luks, MD says:

      Luke… What is “usually” done is that we treat the patient, their complaints and their findings. We put all the info together to come up with a treatment plan. If you and your doctor feel that your knee is stable, then his plan may be appropriate. Without evaluating you, or examining you I can not come up with a specific treatment plan for you.

      Howard Luks

  13. Reply Marc says:

    Hey Howard, great article. Let me tell you my story. About 4 months ago I crashed snowboarding and got a very light partial tear of my ACL. The doctor said it could be that I partially tore it a long time ago and because my knee is stable and everything looks fine (from the outside) to give it some rest. Now here is my problem.whenever I play sports specially the ones that require jumping the next day the back of my knee feels a little sore, right behind it and somewhere close to the beginning of my calf.

    The very next morning I can still participate in sports, in fact once it’s warmed up it doesn’t hurt till the next morning. I am a weekend warrior since I work a lot so on Sunday the pain right in the back of my knee increases.

    I have been taking another month and a half off but it seems like it won’t be any better (don’t know yet). The doctor says my ACL may be a little lose. What do you think?


    • Reply Howard J. Luks, MD says:

      Thanks Marc… At this point if the partial ACL tear was an issue you would have instability, buckling or giving way. It’s unlikely to be the ACL that’s giving you problems. Has your doctor recommended PT?
      Howard Luks

  14. Reply Mike says:


    I plan on going to a doctor soon about this but I was curious about what you might make of my injury. I don’t have any buckling of the sort but I do have pain in my knee and a feeling of torque that isn’t particularly alleviated by changing the position of my foot. This occurs mostly when walking and there are moments when it suddenly increases randomly if I don’t baby that leg. Would this be congruent with a partial tear of some sort? There was no real “moment” when I heard a pop or anything but it’s been going on like this for the last 2-3 weeks now.

  15. Reply Ginger says:

    Hello Dr. Luks,
    Just curious here. I have an ACL tear, my orthopedic doctor was not specific whether partial or complete. No other ligament tears or damage to the mensci. However, I did severely stretch the MCL and have severe bone bruising towards the outer portion of the knee. I have been in physical therapy since one week after my injury.
    My doctor states that it can take up to 6 months before making the decision for surgery. My therapists believes I should have the surgery, he says my knee is still very unstable.
    My knee feels very unstable. About every 15-20 steps, give or take a few, my knee seems to give some as well as the feeling the the knee is pressing more towards the LCL in midstride nearly every step.
    My question is how long would it generally take to know if therapy is truly working or not? (I am at the 5 week mark now.)
    I am moderately active 32 year old. I like to play sports leisurely. Also the mother of a toddler and a special needs child.

    • Reply Howard J. Luks, MD says:

      Hi Ginger.. If you have reasonable motion and strength then you know how your knee is going to behave going forward. It sounds like you have an unstable knee following an ACL tear. As I discuss in my other ACL articles, having a surgeon who is very experienced in ACL surgery is critical. Volume matters. You might want to talk to someone who treats many ACL tears to determine what your next step is. You are at risk of falling… and injuring yourself further if your knee remains unstable.

  16. Reply Gaspare says:

    Just had an Mri to confirm acl damage.I don’t do any contact sports and the pain has been on and off for the last 20 years. I did construction work (manual digging by hand etc) I’ve been office based for the last 10 years. Would this Acl injury be something that has accused over time. 46 years old.


    • Reply Howard J. Luks, MD says:

      Unlikely… no. ACL tears are the result of injuries. It is unlikely that the ACL is the source of your pain.

      • Reply Gaspare says:

        Thank you doctor. Your correct. The problem I have is what the specialist called Patellofemoral. Few weeks strapped up with some physio should do the trick hopefully.


  17. Reply JC says:

    I had a menisectomy in which my surgeon removed about “5%” of my lateral meniscus (my surgery was performed in October). During the procedure he said my acl did not look “right” suggesting I may have a partial ACL tear but that it may have been an old injury since he did not see any blood or fraying in or around the ligament. Since I had no symptoms of instability he/we decided not to touch the acl. So now I am 5 months out of surgery and having trouble comprehending what is wrong with my knee. It still swells only on the lateral aspect and tightens up considerably after high intensity training(squats and running especially). I am an extremely active guy and it’s frustrating not being able to perform at even 70% during my normal activities. I went back to my surgeon about a week ago to tell him about my knee weakness, inflammation, stiffness, and increased crepitus but after he examined my knee again he felt like I should ice and take NSAID’s while trying to push through it. I understand your limitations but any suggestion would help.

    Thank you.

    • Reply Howard J. Luks, MD says:

      Hi JC… 5% isn’t a significant amount of meniscus tissue. Most tears that are symptomatic probably account for nearly 20% of the meniscal volume. Anyway… I would probably consider a second opinion and perhaps a repeat MRI, if indicated.

      Good Luck
      Howard Luks

  18. Reply Luman says:

    Dear doctor,

    I had a mild partial tear in ACl and also a ganglion cyst is seen at the back of my left knee. Doctros told me that I may need to do a arthroscopic procedure to remove that cyst alone and it may be enough to remove the pain I am experiencing while jumping and bending my knee. Will that be enough? pls advice.

  19. Reply Taahir says:

    Hi Doctor ,
    I recently had a injury to the knee playing soccer . Iv waited over 6 weeks to see in any improvement , however my knee could not bend completely . i have been to a ortho doc and have done both x-ray and MRI results are as follows :
    patient shows prominent injury ,partial tear to ACL and mixed typre 2 and 3 tears to medial meniscus. Patient shows early contusion to anterior and posterior of the lateral condyle of the femur.
    The doc says i do not need surgery and should where a brace for 6 weeks and not play soccer for 6 months. i would love to just have your opinion and any further information on this.
    Much appreciated and great article.

  20. Reply Steve says:

    Dear Dr. Luks,

    My daughter injured her acl 2 weeks ago. The MRI revealed some tearing. She is scheduled for surgery on Friday. The Dr was surprised by how stable her knee was in his exam and had to look several times at the MRI as he was surprised it was torn. She did not hear a pop, had little pain after the initial buckle and had no swelling. She is feeling very mobile at this point and feels like she can cut, run etc. she us an 18 year old d1 soccer player. Thoughts?

    Thank You,

  21. Reply subhadip das says:

    after acl torn, my right leg mucles become slim. How it can recover ?

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