Ross Hauser, MD; Danielle Matias, PA-C; Demi Foster, APRN

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 does your knee still feel like it could give way? Maybe your knee bends backward a little further than you think it should.

• 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 is 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 healthcare providers that knee replacement will likely be the ultimate solution down the road.

I had a successful ACL surgery, but I gave up my sports anyway

One of the problems we see in many people who reach out to us is 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 by 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 backward.

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 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, (16) 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. (17)

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”(18)  that led 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 the 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 or 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 to determine how bad off a patient’s knee is. Second what is causing these problems?

A March 2022 study from the Department of Orthopaedic Surgery, Division of Sports Medicine, Midwest Orthopaedics at Rush, Rush University Medical Center was published in the journal Arthroscopy (34) What this study suggested was that patients follow three different rates of Anterior Cruciate Ligament Reconstruction recovery patterns.

• In this study, 245 patients who underwent primary or revision ACLR were divided into classes.
  • Class 1, were patients who had improvement from preoperative to one-year follow-up, with sustained improvement from one to two years postoperatively. This class consisted of 77.1% of the study population (189 patients),
  • Class 2, were patients who demonstrated functional improvement between 1 and 2-year follow-ups, and consisted of 10.2% (25 patients), and
  • Class 3, demonstrated slight improvement at 1-year follow-up with a subsequent decline in International Knee Documentation Committee (IKDC Questionnaire) scores between 1-and 2-year follow-ups, consisting of 12.7% (31 patients) of the study population.

Knee instability that impacts everything from hip to foot, when present, is a high risk for a second ACL rupture.

A May 2020 study in The Journal of Knee Surgery (1) which was then updated in print in September 2021 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 re-tear 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“(2) 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 impacts 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.

Post-surgery knee laxity – the problem of a loose graft

Graft failure is a confusing problem for doctors because they are not sure, other than in situations of obvious tear, what a graft failure is and how it can be treated. The confusion is in the looseness of the laxity of the graft and how do you fix that? An August 2024 study in the journal Current Reviews in Musculoskeletal Medicine (3)  found that “abnormal knee laxity” used 80% of the time to describe graft failure, represented a loose graft, while “graft re-rupture” (37.5%) represented the diagnosis of a ruptured graft.

Knee laxity 6 months after the first ACLR destroys meniscus

A July 2024 study in The American Journal of Sports Medicine (4) of nearly 4700 patients found that “a higher grade of knee laxity 6 months after ACLR was associated with an increased hazard of revision ACLR.” The patients in this study were those who had an ACL injury without other ligament involvement and underwent ACLR surgery with a hamstring tendon autograft. The researchers also found it interesting that knee laxity leads to a progressive increased rate of medial meniscal resection. The study group with the highest grade of postoperative laxity had the highest rate (29.2%) of medial meniscal resection. This finding confirms the essential role of the medial meniscus as a restraint of anterior tibial translation. 

The study found the risk for revision surgery was more than five times higher for Group C (high-level laxity) than for Group A (low-level laxity)

A March 2022 review study of 17,114 Dutch patients who had ACL reconstruction published in the journal Knee Surgery, Sports Traumatology, and Arthroscopy (5) suggests that a loose knee after ACL surgery is a high-risk indicator of revision surgery. In this study, the patients were placed into three groups. Group A (laxity less than 2 mm), Group B (3-5 mm), and Group C (laxity more than 5 mm). The study found the risk for revision surgery was more than five times higher for Group C (high-level laxity) than for Group A (low-level laxity). 

My ACL was fixed great, but now it is my meniscus

Here is a situation we often hear about. It may be a problem affecting you. The ACL surgery went great but now the meniscus “is shot.”

I had ACL reconstruction surgery on my right knee more than 5 years ago. The surgeons congratulated me on having such a successful surgery. As I started rehab and soon afterward my knee really started to hurt. So I went for an x-ray to see if there was a problem with the tunnels or screws. When that showed everything was okay I went for an MRI. The MRI revealed that I developed a bucket handle meniscus tear. The tear was so bad there was nothing that could be repaired, my meniscus was in a state of disintegration.

My doctors still congratulate me on my ACL having healed so well. But now my knee is in a constant state of swelling and they are considering a meniscus transplant.

Now let’s talk about the meniscus – “Meniscus tears seen at the time of anterior cruciate ligament reconstruction are usually asymptomatic.”

Seen frequently in ACL rupture is the meniscus injury. There is a debate as to whether this meniscus injury should be treated or not depending on the extent of the damage to the meniscus. In December 2021 in the medical journal Arthroscopy (6), Orthopedic surgeon K. Donald Shelbourne wrote: “Meniscus tears seen at the time of anterior cruciate ligament reconstruction are usually asymptomatic, and treatment varies greatly between surgeons, with meniscus repair being used for tears that could be left in situ (or alone). Recent outcome studies of most types of lateral meniscus tears show that leaving the tears in situ can give equal or superior results. Meniscus repair being performed for degenerative medial meniscus tears does not give better results than removing the tears. As an alternative to repair, trephination (poking it with a needle) through the meniscus into the peripheral capsule can create many bloody channels to promote healing. Long-term follow-up of meniscus treatment with anterior cruciate ligament reconstruction can help us understand outcomes and prevent us from overtreating tears.”

Allograft or autograft is it undetected PCL damage?

An April 2024 study in the Open Access Journal of Sports Medicine (7) wrote: “There is a convincingly higher re-tear and revision rate in patients who undergo ACLR with allograft than autograft, especially amongst the young, athletic population.” Researchers focused on undiagnosed Posterior Cruciate Ligament (PLC) injury as a common cause of ACLR failure and current literature suggests concurrent operative management of high-grade PLC injuries. Further, the doctors suggest: “Given the high rates of revision surgery in young active patients who return to pivoting sports, (we) recommend strong consideration of a combined ACLR + Anterolateral Ligament (ALL) or Lateral extra-articular tenodesis (LET) procedure in this population.”

Tunnel placement complications

Tunnel problems are one of the problems where revision surgery is most likely warranted.

• Tunnel widening (the hole gets bigger),
  • 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.

A June 2023 study in the journal BMC Musculoskeletal Disorders (8) examined the bone landmark positioning method used to position the femoral tunnel during anatomical reconstruction surgery in patients with anterior cruciate ligament (ACL) rupture. Eighty-four eligible patients (84 knees) were included in this study. The goal of the study was to see if the bony landmarks put the tunnels in the right position. The findings of this study showed that when using conventional bone landmark positioning methods, for positioning the femoral tunnel in ACL reconstruction, the position of the bone tunnel could easily deviate and the accurate rate of bone tunnel position was low. The function scores and stability of the knee joint were both lower in patients with poor femoral tunnel positions compared with those with good femoral tunnel positions. The overall rate of patients who had a good rate of good position was only 26.2%.

A February 2024 editorial in the journal Arthroscopy (9) wrote: “The number one cause of failure is a misplaced ACL femoral tunnel. Tunnel malposition leads to a higher incidence of postoperative meniscal lesions, inferior clinical outcomes, and higher revision rates.” However, the doctors also wrote that not every patient has a favorable anatomy to correct tunnel placement. The editorial continues: “Identifying risk factors for failure is undoubtedly a step in the right direction. However, what we really need is solutions for intraoperative problems and for patients with unfavorable anatomy.

Why do doctors want to avoid revision surgery – for one it’s 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: (10)

• Researchers compared 56 patients undergoing a revision reconstruction (the surgery after the first ACL surgery) to 52 patients undergoing 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 (11), 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 technical 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.

Post-surgery, post-traumatic knee osteoarthritis

The problems of surgery causing osteoarthritis are well documented and many. A November 2023 study in the journal Physical Therapy Research (12) writes: “. . . more than half of ACL injuries lead to post-traumatic osteoarthritis, and some factors during ACLR should also be considered risk factors for post-traumatic osteoarthritis. Older and overweight patients are risk factors for post-traumatic osteoarthritis because of cartilage degeneration and high mechanical force damaging the sub-chondral of femoral and tibial bones, respectively. Patients with ACL injuries that cause meniscus tears and cartilage defects had a higher risk of getting post-traumatic osteoarthritis than those with a sole ACL injury after the ACLR. Several strategies can prevent poor knee function and PTOA after ACLR, including a pre-operative program, comprehensive rehabilitation, body weight control, and return to sport consideration based on physical capacity, proper time, and psychological readiness.”

Shouldn’t ACL reconstruction prevent posttraumatic osteoarthritis?

A September 2021 German study in the journal (translated into English) Sports Injury – Sports Damage (13) wrote: “The treatment of an anterior cruciate ligament rupture is still controversial. In particular, this applies to the question of conservative versus surgical treatment. The answer to this question is often based on consequential damage such as the development of posttraumatic osteoarthritis, secondary damage to the meniscus or cartilage, and participation in sports. ”

To answer this question, the researchers reviewed previously published studies and found: “Patients with an anterior cruciate ligament rupture are likely to be at a greater risk of developing progressive joint degeneration. A protective effect of cruciate ligament surgery has not been found in the evaluated studies. A general argument in favor of cruciate ligament surgery aiming to achieve a protective effect on hyaline articular cartilage seems obsolete based on the results and should therefore not be used in patient education in the future.”

Simply anterior cruciate ligament reconstruction does not appear to prevent posttraumatic osteoarthritis.

This was also suggested by a September 2021 paper in The Bone & Joint Journal (14) which also simply states: “Anterior cruciate ligament (ACL) rupture commonly leads to post-traumatic osteoarthritis, regardless of surgical reconstruction.”

ACL reconstruction and the development of posttraumatic osteoarthritis in more active people

A February 2021 study in The American Journal of Sports Medicine (15) assessed the association between activity level after ACL reconstruction (ACLR) and the development of posttraumatic osteoarthritis. The focus of this study was to investigate the relationship between patient-reported outcomes and progressive cartilage degenerative changes three years after ACL reconstruction.

• Sixteen patients (45.7%) showed evidence of cartilage degeneration at 3 years, most frequently in the medial compartment (the inside knee 34%).
• Increased activity at 3 years after ACL reconstruction was significantly associated with increased risk of medial compartment posttraumatic osteoarthritis.

In this study, the researchers used the MARX scale to determine a consistent level of activity. Patients who reported greater amounts of running, deceleration, cutting, and pivoting were more likely to develop posttraumatic osteoarthritis.

Depression and anxiety in patients needing a second ACL surgery

A September 2023 study (16) suggested women/girls and those needing secondary ACL surgery are at increased risk of postoperative depression/anxiety. Nearly one in seven young females are diagnosed with depression/anxiety after ACLR. The researchers noted that one in seven is likely an underestimate as mental health problems are underreported, undertreated, and understudied. The paper concludes: “The orthopedic community must be cognizant of the increased risk of postoperative mood disorders for females and those who suffer a secondary ACLR, and these results suggest that screening for depression and anxiety for these at-risk populations with referral to mental health professionals for appropriate care may be warranted.”

 

References

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Post-traumatic osteoarthritis

A November 2023 study (51) found older and overweight patients to have higher risk factors for post-traumatic osteoarthritis because of cartilage degeneration and high mechanical force (weight) damaging the sub-chondral of femoral and tibial bones, respectively. Patients with ACL injuries that caused meniscus tear and cartilage defects had a higher risk of getting post-traumatic osteoarthritis than those with a sole ACL injury after the ACL reconstruction.