After ACL Reconstruction: Complication and post-surgery treatment options: Do you need revision surgery?
Ross Hauser, MD, Caring Medical Florida
David N. Woznica, MD, Caring Medical Regenerative Medicine Clinics, Oak Park, Illinois
Danielle R. Steilen-Matias, MMS, PA-C, Caring Medical Florida
After ACL Reconstruction, Complications and post-surgery knee instability treatments
When the other knee ligaments are too weak to support the new ACL, this causes ACL surgery failure.
In this article, we will discuss problems of knee instability following anterior cruciate ligament reconstruction surgery and review various non-surgical or revision treatment suggestions to stabilize the unstable post-ACL surgical knee.
ACL reconstructive surgery works for many patients. But how do we define the definition of “works?” Was the surgery successful but your knee still feels like it could give way? Maybe your knee bends backward a little further than you think it should. If so, was your surgery then really that successful?
- Maybe you did have a successful surgery, however, as you are reading this article you are likely researching problems of an unstable knee that is preventing you from doing sports, work, or other daily routines.
- For some of you, it is likely that if you are reading this article, you had a less than successful surgery, your knee is very unstable and you are looking for answers that go beyond buying one knee brace after another.
Many patients that we see following an anterior cruciate ligament reconstruction surgery are confused. They thought for sure once they had the ACL surgery that they would be back to doing what they were doing with the same, if not better, knee than they had before the surgery. This despite the fact that their surgeon probably advised them of possible post-surgery problems, such as instability and the need for extensive rehabilitation.
Other patients recognized immediately that their surgery did not go that well. In immediate post-op rehabilitation, they suffered and may continue to suffer from post-surgical complications. They too are looking for answers beyond knee braces, extended physical therapy, painkillers and the constant reminders from their health care providers that knee replacement will likely be the ultimate solution down the road.
The appeal and enthusiasm for ACL reconstruction surgery, is this misguided?
A patient will say: “What other choice did I have, BUT to get the surgery?”
Many times we will see a patient following anterior cruciate ligament reconstruction. To these patients we ask a simple question:
- “Why did you have the surgery?”
Many times the patient will give an equally simple answer:
- “What other choice did I have?”
There are options to the ACL surgery and revision surgery as we will discuss below:
I had a successful ACL surgery, but I gave up my sports anyway
Later in this article we will discuss making ACL surgery outcomes more successful with various non-surgical options.
One of the problems we see in may people who reach out to us is an unrealistic expectations of what the surgery will do for them. Watching professional athletes return from “career-threatening,” ACL injuries is somewhat normal. So is that what a non-professional athlete should expect?
In 2014 surgeons wrote in the journal International orthopaedics: (1) “the revision ACL reconstruction procedure offers improvement in subjective and objective outcomes. Lack of improvement in sports participation was noted in non-professional athletes and patients who downgraded their sports participation opting for non-contact sports.”
You may think that that study was in 2014, things must have improved by now. In a sense you may think they went backwards.
Ten years later – still looking for explanations as to why many people need a second ACL reconstruction surgery
A May 2020 study in The journal of knee surgery (2) went looking for answers by way of what doctors and researchers were looking up in the National Institutes of Health’s library at PubMed.gov to explain why: “The rate of anterior cruciate ligament retear remains high and revision ACL reconstruction has worse outcomes compared with primaries.”
What paper did the surgeons overwhelmingly refer to? A 2010 study titled: “Biomechanical Measures During Landing and Postural Stability Predict Second Anterior Cruciate Ligament Injury After Anterior Cruciate Ligament Reconstruction and Return to Sport“(3) What did this paper say?
“The findings of the current study support the tested hypothesis that altered neuromuscular control patterns during landing and deficits in postural stability predict subsequent ACL injuries in a sample of athletes at the time of return to sport after initial ACLR. Specifically, transverse plane net moment impulse at the hip, dynamic frontal plane knee range of motion, side-to-side differences in sagittal plane knee moment at initial contact, and deficits in postural stability predicted a second ACL injury with both high sensitivity and specificity.”
In other words, knee instability that impacted everything from hip to foot, when present, is a high risk for a second ACL rupture. Preventing this knee instability, as we will discuss below, is paramount to preventing the second ACL rupture.
The second ACL surgery or “revision surgery” is a very popular procedure. It is also much less “successful.” Especially for the adolescent athlete
You are a young athlete, you are the parent of a young athlete, the clock is always ticking because a young athlete’s career is finite in years. There is a great sense of urgency to get the knee repaired ASAP. So the appeal to revision surgery is very strong.
We are going to take a little research journey. The purpose it to demonstrate how surgeons for the last 10 years have struggled with ACL revision surgery.
- Doctors writing in the American Journal of Sports Medicine (4) suggest that younger patients had a higher risk of revision ACL reconstruction than older patients and that subjective clinical outcome was worse after revision ACL reconstruction compared to primary ACL reconstruction.
- Even though the second surgery was performed to fix the first surgery. You still had a high risk of being worse off after the second surgery.
- They report that nearly 9% of patients under 20 need a second anterior cruciate ligament (ACL) Reconstruction Therapy.
- Doctors reporting in the journal Clinical Orthopaedics and Related Research (5) also suggest that young, active, skeletally mature patients have higher failure rates after various surgical procedures, including primary ACL reconstruction.
- While a single-stage transosseous revision (ACL tunnel repair surgery) restores knee stability, only 52% of these patients return to their prior level of activity or sport.
Surgeons at the University of California San Francisco issued these observations in the journal Current reviews in musculoskeletal medicine.(6)
- With an increase in high-demand sporting activity, the rate of pediatric and adolescent ACL reconstruction is increasing. Yet, the failure rates after reconstruction are much higher than the adult population.
- An understanding of the ACL surgery failure should begin with:
- an assessment of post-operative patient compliance and sporting activity. (Is the patient getting apportionment rehab following the surgery to begin competing again?)
- Is it poor tunnel placement and poor graft size/type?
- Concurrent bony deformity must also be addressed including lower extremity valgus alignment and tibial slope abnormalities. (Was the anatomical alignment of the ACL reconstruction correct or did the surgery itself create a misalignment?)
- Meniscus and chondral injury must be aggressively treated.
- Furthermore, imaging must be examined to look for missed posterolateral corner injury. (There is much more damage to the knee beyond the ACL tear in the posterolateral corner of the knee. This includes:
- lateral collateral ligament (LCL)
- popliteus tendon
- popliteofibular ligament
- meniscofemoral and meniscotibial ligaments
- the biceps femoris
- the iliotibial band (ITB)
- among other structures.
Tunnel placement complications
If you had the ACL surgery you likely know all about tunnels. This is a significant complication of ACL reconstruction. As we are looking for solutions to your problem in this article we will only touch on this briefly. Tunnel problems are one of the problems where revision surgery is most likely warranted.
- Tunnel widening (the hole gets bigger),
- and tunnel misplacement (the tunnel was put in the wrong place),
- and fracture (the tunnel hole was too wide and caused a fracture of the bone) are the more common complications.
During the ACL reconstruction surgery, a hole is drilled in the thigh bone and the shin bone, the donor tendon that is being used as the graft is then threaded through the holes, through the knee and fixed or screwed into place.
Why doctors want to avoid a revision surgery – for one its the inferior results
2013: Why doctors want to avoid a revision was pointed out in a study out of Norway in the journal Knee Surgery, Sports Traumatology, Arthroscopy: (7)
- Researchers compared 56 patients undergoing a revision reconstruction (the surgery after the first ACL surgery) to 52 patients undergoing a primary reconstruction surgery, (the first surgery),
- The results showed that the patients who had the second surgery had inferior results in almost every category of observation, including greater laxity, less muscle strength, and more severe radiological osteoarthritis.
August 2020: In the medical journal Orthopaedic surgery (8), orthopedic surgeons published their findings and observations on possible inferior results achieved in revision or second ACL reconstruction surgery. Here are the summary learning points:
- “More revisionary reconstruction procedures are required following failing anterior cruciate ligament (ACL) reconstructions, which are often regarded as a technique challenge with very limited goals.”
- “Revision ACL reconstruction could provide patients with excellent restoration of knee outcomes compared to the status before revision.” Comment: It is possible the second surgery can improve the knee function after the first attempt failed
- “Also, while knee function in the revision group was inferior to the primary group, knee stability was equivalent between the two groups at the final follow-up.’ Comment: The first failed surgery and the revision surgery provided equal knee stability, despite the second surgery being inferior in helping function.
The more revision surgeries, the less sports
The Department of Orthopedic Surgery at the Mayo Clinic published findings in the American Journal of Sports Medicine.(9) Here they write: “Continuously increasing numbers of primary anterior cruciate ligament reconstructions invites a parallel increase in graft failures and need for revision ACL reconstruction surgery. High failure rates has previously stigmatised the revision surgery. . . Good outcomes of revision ACL reconstruction surgery are achievable. The use of different graft types did not affect the outcome of the procedure. Most of the patients opted to less aggressive sports participation after the revision procedure.”
Avoiding “Revision – Revision” – the Third ACL surgery – Back in the tunnels
Multiple studies have shown that the rate of return to the pre-injury level of sport is significantly lower following revision ACLR than following primary ACLR procedures.
In 2017, doctors writing in The Journal of Bone and Joint Surgery (10) suggest that it is important for orthopedic surgeons to attempt to restore proper anatomy and biomechanics during revision (the second ACL surgery) ACLR to minimize the rate of re-revision. (The third ACL surgery). Here are the surgeon’s checklist of guidelines.
- They write that: Technical errors such as non-anatomic tunnel placement are some of the most common causes of graft failure after primary anterior cruciate ligament reconstruction.
- When considering a revision ACLR in a patient with ACL graft failure, it is crucial to perform preoperative imaging, which should include an initial radiographic series, magnetic resonance imaging, and possibly computed tomography for further assessment of tunnel locations.
- Revision ACLR may be performed in a 1 or 2-stage procedure depending on the size and location of the existing tunnels, bone stock, existing hardware, and infection status.
- Use of autograft (patient) ligament tissue for revision ACLR has been shown to correlate with higher patient-reported outcomes and a significantly lower risk of subsequent graft rupture in comparison with allograft (donor) use.
- Multiple studies have shown that the rate of return to the pre-injury level of sport is significantly lower following revision ACLR than following primary ACLR procedures.
It is important to consider that the findings above are considered excellent ACL reconstruction patient results. We ask, do these findings really merit an excellent? Here is more research to review:
- ACL Reconstruction and the Meniscus: In the medical journal Arthroscopy, (11) doctors wrote: “Meniscectomy was performed in 65% of ACL tear procedures. This is concerning because studies have shown that, regardless of knee stability obtained after ACL reconstruction, meniscectomy accelerates degenerative joint changes“.
- ACL Reconstruction and Patellofemoral pain syndrome: Doctors writing in the journal Arthritis care & research, (12) note that Patellofemoral osteoarthritis is common following anterior cruciate ligament reconstruction and that post-surgical lack of knee rotation may be sufficient to initiate or accelerate patellofemoral cartilage degeneration.
Ten years later, my knee is still not the same
Some people do very well with ACL reconstruction surgery, some do very well with second or revision ACL surgery. Some do well with the third ACL reconstruction/revision surgery. These are typically not the people we see in our office. We see the people who may have had a successful surgery, but their knee is not the same. They tell us stories like this one:
When I had the ACL reconstruction I had a difficult rehab. Maybe because I was pushing myself too hard. My knee just did not feel right. Almost a year after the surgery, the graft gave way and it pretty much wiped out my meniscus. In the revision surgery a tendon graft was used and most of my meniscus, which I was told was beyond repair, was removed. The surgery was a great success but my knee was never the same. I never really recovered. Here I am 10 years later now being managed along until I can get a knee replacement.
The fact that your knee is moving towards inevitable knee replacement should tell you that every day your knee is getting weaker.
By this time you can see that we are building an argument that instability in the ACL Reconstructed knee leads to a more accelerated breakdown of the knee. This does not have to be solely an osteoarthritis knee replacement someday in the future, it is a problem you have today. But knee replacement is the general direction you are moving in. The fact that your knee is moving towards inevitable knee replacement should tell you that every day your knee is getting weaker.
- Researchers writing in the British Journal of Sports Medicine (13) found that if you had to have a revision or secondary ACL reconstruction surgery you were at advanced risk for osteoarthritis, ligament damage and weakness, and loss of knee function.
- In fact, doctors writing in the Journal of Bone and Joint Surgery (14) wrote: “Despite the success of restoring joint stability and improving early functional outcomes after anterior cruciate ligament reconstruction, the long-term risk of developing symptomatic osteoarthritis requiring total knee replacement is higher than that in the uninjured population.”
Many people have issues with knee instability and function after anterior cruciate ligament reconstruction, it is not just you.
We have just presented a lot of research on the problems some patients have following ACL reconstruction surgery. But in reality, how often do ACL reconstruction complications and post-surgical concerns occur? If you are reading this article because you are considering an ACL surgery, you may think to yourself, how many people does this really affect?
For you who had the surgery, it has happened one time too many because you have a lot of knee problems. While you may be led to believe that this is a problem you suffer from a small minority of patients, it is NOT just you, it is a lot of patients. How big a problem is this in the medical community? Consider this:
In 2015, a paper appeared in the journal Clinical Orthopedic Sports Medicine, (15) it came from researchers at Johns Hopkins University. The researchers looked at all the medical studies published in the field of clinical sports medicine with the goal of finding the top 100 most cited medical articles. This was not just a study in statistics, the subject matter of the top 100 articles would tell doctors and other health professionals what some of the biggest challenges in medicine were and how researchers were moving toward possible solutions.
- 15 of the 100 ( a very heavy influence) dealt with an injury to the ACL.
In 2017, European researchers looked solely at the top ACL 50 articles. They published their results in the journal International Orthopaedics.(16)
The top three articles cited were articles that were related to defining a scoring system to help clinicians understand the severity of symptoms related to knee ligament problems. The number 1 article was the 1985 “Rating systems in the evaluation of knee ligament injuries”(17) that lead to the “Tegner Lysholm Knee Scoring Scale.” A questionnaire to grade and assess the patient’s knee problems.
Now if you had an ACL reconstruction and you are experiencing continued problems, you may have been given the questionnaire or were asked questions that pertain to these following problems broken up into these sections.
- Section 1 – Do you Limp?
- Section 2 – Do you need help with walking? Do you use a cane, a crutch, can you support your own weight without assistance?
- Section 3 – How much pain do you have? How much pain do you have after certain levels of exertion?
- Section 4 – Instability – when does your knee “give out”? Always? Never? At certain amounts of exertion?
- Section 5 – To what extent does your knee lock up?
- Section 6 – To what extent does your knee swell? Is swelling constant?
- Section 7 – Can you climb stairs?
- Section 8 – Can you squat?
Based on the amount of time clinicians spend researching and citing articles on “Knee scoring systems, one could suggest that the biggest problem facing the clinician is how do you determine how bad off a patient’s knee is? Second what is causing these problems?
What if I buy a really good brace? Study: Knee bracing does not appear to improve the clinical outcomes on the function and stability for ACL-reconstructed knees
An October 2019 study in the journal Orthopaedics and traumatology, surgery and research (18) suggests that “knee braces could not provide superior clinical outcomes on knee functional scores and stability evaluations.”
Here is what they said:
- “Knee brace has been commonly used as a device to protect the graft after reconstruction of anterior cruciate ligament (ACL). Studies have focused on the effects of braces after ACL reconstruction, and controversial results were reported.”
In this study the researchers combined data from seven studies with 440 participants. After examining the patient outcomes following ACL reconstruction outcomes, the research team found:
- “Knee bracing does not appear to improve the clinical outcomes on the function and stability for ACL-reconstructed knees. Thus, bracing for patients treated with ACL reconstruction should not be recommended routinely.“
It is time to talk about the other ligaments of the knee –
When the other knee ligaments are too weak to support the new ACL, this causes ACL surgery failure.
The ACL ligament does not sit in isolation. Your problem may be a knee ligament problem and it is not just the ACL, it is the other ligaments.
The four major ligaments of the knee are:
- the anterior cruciate ligament (ACL),
- the posterior cruciate ligament (PCL),
- the medial collateral ligament (MCL),
- the lateral collateral ligament (LCL).
- The wildcard in this is a 5th knee ligament, the “rogue influence” and “controversial” anterolateral ligament.
Study: “Generalized Hypermobility, Knee Hyperextension, and Outcomes After Anterior Cruciate Ligament Reconstruction”
Let’s examine an October 2017 study in the medical journal Arthroscopy (19) led by the Minnesota Orthopedic Sports Medicine Institute and Department of Orthopedics, University of Michigan MedSport.
The title of the paper should say it all: Generalized Hypermobility, Knee Hyperextension, and Outcomes After Anterior Cruciate Ligament Reconstruction.
Here are the summary findings:
- Doctors looked at 183 (knees) patients two years removed from ACL reconstruction
- Patients underwent ACLR with either bone-patellar-tendon autograft, quadrupled hamstring autograft or allograft tissue.
Knee Hypermobility – instability
- Of the 183 patients:
- Forty-one of 183 consecutive patients were categorized as hypermobile.
- The remaining 142 were categorized as non-hypermobile.
- ACL reconstruction failure was higher in the Hypermobile group (24.4% failure rate) compared with the Non-hypermobile group (7.7% failure rate)
- The overall ACL injury rate (ACL graft injury, excessive graft laxity, plus contralateral (the other knee) ACL tear) was higher in the Hypermobile group (34.1%) compared with the Non-hypermobile group (12.0%)
In this above study, the focus is put on the ACL graft being too loose or lax. The new ACL is not holding the knee together as it should and this is causing whole knee instability.
- BUT, what if the ACL graft was put into a knee that was already suffering from ligament laxity from the other ligaments?
“Preoperative laxity of the knee” and “Excessive graft laxity” as a cause of ACL surgery failure
Let’s go back to 2001 and a well-documented summary of ACL complications that can be found in the abstract of a classic lecture presentation from Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh. This lecture was delivered in 2001. (20)
From 2001: “Many factors influence the overall success or failure of anterior cruciate ligament reconstruction, including the integrity of the secondary restraints (that is the supporting structures of the knee), the collateral ligaments, the mid-third capsular ligaments, the meniscus, and the iliotibial band), the preoperative laxity of the knee, the status of the articular and meniscal cartilage. . . “
As we noted in the research above untreated associated ligaments insufficiencies, in other words, the other knee ligaments were too weak to support the new ACL, this caused failure.
The prevalence of knee hyperextension (knee instability) in ACL revision surgery patients
We are now going to move forward to an October 2018 in the American Journal of Sports Medicine.(21)
This is a huge study listing dozens of authors. The study’s abstract lists that the investigation was performed at The Carrell Clinic, Dallas, the Department of Orthopaedics, Washington University School of Medicine, St Louis, the Department of Orthopaedics and Rehabilitation, Vanderbilt University Medical Center, and Reedsburg Area Medical Center, Reedsburg, Wisconsin.
The researchers in this study were presenting a hypothesis about the impact of knee hyperextension in revision ACL reconstruction surgery. Knee hyperextension being defined as a 5 degree ability to bend the knee backward.
So the researchers went about examining ACL reconstruction patients for two years.
- The average age of the patient was 26 years old
- 42% of patients were female
- There were 50% autografts, 48% allografts, and 2% that had a combination of autograft plus allograft.
- Graft rupture was more prevalent in:
- Younger patients
- Those patients who used allograft
- and patients who had hyperextension of greater than 5 degrees.
Conclusion of the study?
- This study revealed that preoperative physiologic passive knee hyperextension of greater than 5 degrees is present in one-third of patients who undergo revision ACLR.
- Knee hyperextension of greater than 5 degrees is an independent significant predictor of graft failure after revision ACLR with a more than 2-fold risk of subsequent graft rupture in revision ACL surgery.
The road to preventing ACL revision surgery – ligament strengthening
In this video Ross Hauser, MD explains a simple injection technique – Prolotherapy for strengthening the ACL
Video transcript summary:
- For Grade 1 and Grade 2 tear of ACL, Prolotherapy injections can be an effective non-surgical option
- If somebody has a complete anterior cruciate ligament tear they should get surgery to repair it but then after surgery Prolotherapy should considered because prolotherapy will stimulate the healing and strengthening of the attachments of the transplanted ACL. There are two attachments of the anterior cruciate ligament – at the tibial tubercle and at the lateral femoral condyle. Prolotherapy strengthens these attachment points.
- Prolotherapy is very effective at decreasing the pain, knee instability and the inability to exercise that occurs with ACL weakness or injury.
- Athletes and non-athletes – people with physically demanding work can continue to train or work during treatment – there is typically no reason for immobilization.
The regenerative approach to Knee ligament weakness and degenerative injury
Throughout this article, we demonstrated research from the surgical community that discusses the problems of knee instability following an ACL reconstruction surgery. These problems can be severe enough that a second or even third surgery may be suggested. We have also demonstrated that these revision surgeries are, for the most part, less successful than the patient expects.
The problem of knee instability is a problem of damaged, untreated degenerative structures. This includes the three other main stabilizing ligaments in the knee the MCL, PLC, and LCL.
In the case of an overstretched or partially torn ligament, a treatment approach to strengthen and heal the injured ligament should be utilized. The treatment that stimulates ligament healing and regeneration is Prolotherapy.
In this video, Danielle R. Steilen-Matias, MMS, PA-C, of Caring Medical demonstrates how we treat a patient with primary complaint of knee osteoarthritis.
- The person in this video is being treated from knee osteoarthritis as the primary complaint. The treatment takes a few minutes. The person in this video is not sedated and tolerates the treatment very well. For some patients, we do provide IV or oral medications to lessen treatment anxiety and pain.
- The first injection is given into the knee joint. The Prolotherapy solution is given here to stimulate repair of the knee cartilage, meniscal tissue, and the ACL as well.
- The injections continue over the medial joint line making sure that all the tendons and ligaments such as the medial collateral ligament are treated.
- This patient reported the greatest amount of pain along the medial joint line. This is why a greater concentration of injections are given here.
- The injections continue on the lateral side of the knee, treating the lateral joint line all the tendon and ligament attachments there such as the LCL or lateral collateral ligament.
This article continues with non-surgical options > Is ACL reconstruction the only option?
If you have questions about ACL reconstruction options, you can get help and information from our Caring Medical Staff
1 Mahmoud SS, Odak S, Coogan S, McNicholas MJ. A prospective study to assess the outcomes of revision anterior cruciate ligament reconstruction. Int Orthop. 2014;38(7):1489‐1494. doi:10.1007/s00264-014-2324-z [Google Scholar]
2 Ennis HE, Bondar K, McCormick J, Chen CJ, Donnally CJ 3rd, Kaplan L. The 50 Most Cited Articles in the Indications, Risk Factors, Techniques, and Outcomes of ACL Revision Surgery [published online ahead of print, 2020 May 5]. J Knee Surg. 2020;10.1055/s-0040-1702182. doi:10.1055/s-0040-1702182. [Google Scholar]
3 Paterno MV, Schmitt LC, Ford KR, Rauh MJ, Myer GD, Huang B, Hewett TE. Biomechanical measures during landing and postural stability predict second anterior cruciate ligament injury after anterior cruciate ligament reconstruction and return to sport. Am J Sports Med. 2010 Oct;38(10):1968-78. doi: 10.1177/0363546510376053. Epub 2010 Aug 11. PMID: 20702858; PMCID: PMC4920967. [Google Scholar]
4 Lind M, Menhert F, Pedersen AB. Incidence and Outcome After Revision Anterior Cruciate Ligament Reconstruction. Am J Sports Med July 2012 vol. 40 no. 7 1551-1557 [Google Scholar]
5 Reinhardt KR, Hammoud S, Bowers AL, Umunna BP, Cordasco FA. Revision ACL reconstruction in skeletally mature athletes younger than 18 years. Clin Orthop Relat Res. 2012 Mar;470(3):835-42. [Google Scholar]
6 Garcia S, Pandya NK. Anterior Cruciate Ligament Re-tear and Revision Reconstruction in the Skeletally Immature Athlete. Curr Rev Musculoskelet Med. 2020;13(3):369‐378. doi:10.1007/s12178-020-09627-x [Google Scholar]
7 Gifstad T, Drogset JO, Viset A, Grontvedt T, Hortemo GS. Inferior results after revision ACL reconstructions: a comparison with primary ACL reconstructions. Knee Surg Sports Traumatol Arthrosc. 2012 Dec 14 [Google Scholar]
8 Yan X, Yang XG, Feng JT, Liu B, Hu YC. Does Revision Anterior Cruciate Ligament (ACL) Reconstruction Provide Similar Clinical Outcomes to Primary ACL Reconstruction? A Systematic Review and Meta-Analysis [published online ahead of print, 2020 Aug 13]. Orthop Surg. 2020;10.1111/os.12638. doi:10.1111/os.12638
9 Griffith TB, Allen BJ, Levy BA, Stuart MJ, Dahm DL. Outcomes of repeat revision anterior cruciate ligament reconstruction. The American journal of sports medicine. 2013 Jun;41(6):1296-301.[Google Scholar]
10. Kraeutler MJ, Welton KL, McCarty EC, Bravman JT. Revision Anterior Cruciate Ligament Reconstruction. JBJS. 2017 Oct 4;99(19):1689-96. [Google Scholar]
11. Noyes FR, Barber-Westin SD. Treatment of meniscus tears during anterior cruciate ligament reconstruction. Arthroscopy. 2012 Jan;28(1):123-30. doi: 10.1016/j.arthro.2011.08.292. Epub 2011 Nov 9. [Google Scholar]
12 Culvenor AG, Schache AG, Vicenzino B. Are knee biomechanics different in those with and without patellofemoral osteoarthritis after anterior cruciate ligament reconstruction? Arthritis Care Res (Hoboken). 2014 Oct;66(10):1566-70. [Google Scholar]
13 Grassi A, Ardern CL, Marcheggiani Muccioli GM, Neri MP, Marcacci M, Zaffagnini S. Does revision ACL reconstruction measure up to primary surgery? A meta-analysis comparing patient-reported and clinician-reported outcomes, and radiographic results. Br J Sports Med. 2016 Jan 25. [Google Scholar]
14 Watters TS, Zhen Y, Martin JR, Levy DL, Jennings JM, Dennis DA. Total Knee Arthroplasty After Anterior Cruciate Ligament Reconstruction: Not Just a Routine Primary Arthroplasty. J Bone Joint Surg Am. 2017 Feb 1;99(3):185-189. [Google Scholar]
15 Nayar SK, Dein EJ, Spiker AM, Bernard JA, Zikria BA. The Top 100 Cited Articles in Clinical Orthopedic Sports Medicine. Am J Orthop (Belle Mead NJ). 2015 Aug;44(8):E252-61. [Google Scholar]
16 Vielgut I, Dauwe J, Leithner A, Holzer LA. The fifty highest cited papers in anterior cruciate ligament injury. International orthopaedics. 2017 Jul 1;41(7):1405-12. [Google Scholar]
17 Tegner Y, Lysholm J. Rating systems in the evaluation of knee ligament injuries. Clinical orthopaedics and related research. 1985 Sep(198):43-9. [Google Scholar]
18 Yang XG, Feng JT, He X, Wang F, Hu YC. The effect of knee bracing on the knee function and stability following anterior cruciate ligament reconstruction: A systematic review and meta-analysis of randomized controlled trials. Orthopaedics & Traumatology: Surgery & Research. 2019 Oct 1;105(6):1107-14.
19 Larson CM, Bedi A, Dietrich ME, Swaringen JC, Wulf CA, Rowley DM, Giveans MR. Generalized Hypermobility, Knee Hyperextension, and Outcomes After Anterior Cruciate Ligament Reconstruction: Prospective, Case-Control Study With Mean 6 Years Follow-up. Arthroscopy: The Journal of Arthroscopic & Related Surgery. 2017 Jun 7. [Google Scholar]
20 Harner CD, Giffin JR, Dunteman RC, Annunziata CC, Friedman MJ. Evaluation and treatment of recurrent instability after anterior cruciate ligament reconstruction. Instr Course Lect. 2001;50:463-74. [Google Scholar]
21 MARS Group, Cooper DE, Dunn WR, Huston LJ, Haas AK, Spindler KP, Allen CR, Anderson AF, DeBerardino TM, Lantz BB, Mann B. Physiologic Preoperative Knee Hyperextension Is a Predictor of Failure in an Anterior Cruciate Ligament Revision Cohort: A Report From the MARS Group. The American journal of sports medicine. 2018 Jun 1:0363546518777732. [Google Scholar]