Although reconstruction of a torn anterior cruciate ligament reconstruction has become much more common and is generally very successful in the 1990's, the decision to do it should ultimately be an individual one. In this discussion, I will try to outline what I believe every patient with a torn anterior cruciate ligament should be aware of and should think about.

All ACL tears, knees, and patients are not equal

Surgical outcomes are complex to analyze largely because there are so many variables to consider. Although recently much effort has gone into trying to reliably and reproducibly describe surgical outcomes so that insurers and patients can try to make better decisions, the process is still in its infancy. Fundamentally, that's because a satisfactory outcome for a professional athlete may be very different from a satisfactory outcome for a recreational water skier and hiker.

But that's only a part of the story. For reasons we still don't clearly understand, some people with a torn anterior cruciate have very little difficulty (after they recover from the acute injury) using their knee normally, while other people with exactly the same degree of injury, have frequent problems. Then, there are all the shapes, sizes, and underlying conditions that ACL injured knees come in. Picture four different people who might present with anatomically identical completely torn ACL's. One is a 115 pound, 15-year-old girl who injures her knee downhill skiing for the first time. Another is a 36 year old professional football player, who has had 2 previous knee "scopes" for torn cartilage (menisci) and who injures that same knee when he's tackled by two 280 pound linemen. A third is a 52 year old fitness instructor, who has run 4 previous marathons, and who competed as a cross country ski racer from age 10 to age 25 - and who injures her knee while hiking when she slips on a wet rock. Finally, a fourth is a 28 year old, moderately overweight and admittedly non-athletic person who sustains a knee injury by slipping on a spilled jar of applesauce at the supermarket. Obviously, one could describe dozens more, all with the anatomic injury - but all very different.

Precisely because there are so many critically important differences within any group of people who have torn their anterior cruciate ligament, every experienced orthopaedic surgeon knows that you must try to take into account as many of the important variables as possible, and must try to tailor both the explanation and the treatment to each person’s individual circumstances.

An old injury vs. a new injury

The most fundamental and most common outcome of tom anterior cruciate ligament is a knee that is looser than it was before the injury. The normal anterior cruciate ligament guides and restrains the motion of the knee within a very small 2-5mm range. Unfortunately, tearing is usually an "all or none" phenomenon except in very rare circumstances when only part of the ligament actually tears. Unless the tom fibers then line up exactly in the position they were in before tearing, and stay that way without moving or pulling apart for the 6 or more weeks it takes for ligament tissue to heal, the result is either a healed ligament which is quite strong but too long to function as it should, or a very flimsy ligament - or sometimes no healing at all if the tom fibers are in poor contact or don't stay still enough to heal well. Ligaments are not capable of regenerating or "shortening" or "tightening up" during healing.

Many patients, then, experience a sense of instability in their knees after ACL injury, particularly when the knee is subjected to the higher loads of jumping, landing, planting and pivoting, or rapid acceleration or deceleration. Under those circumstances, but rarely with the lesser loads of everyday activities, the knee will "give out", sometimes very painfully and accompanied by a fall, and sometimes with minimal pain and only a slight sensation of "slipping". A generation or two ago, before surgery was a good option, people who tore their anterior cruciate ligaments often lived with what everyone described as a "trick" knee. Many of those people got used to it and controlled it as best they could by avoiding those motions and loading patterns that caused the knee to mal-function. Even now, some patients deliberately will choose to try to get along with their "trick" knees rather than undergo surgical reconstruction, and some people find that a very acceptable solution. Some have very infrequent episodes of "giving way" and some none at all. Some get so good at avoiding the wrong loading patterns that they don't even realize they're doing it

It appears though, that in virtually all patients who have tom their ACL's, the knee does not function properly, even if the abnormal motions are very subtle and imperceptible. I often describe the situation as being analogous to a car with the tires unbalanced. When the vehicle is going slow, the abnormal motion (shimmy) is imperceptible; but when the vehicle is going faster with higher loads, the abnormal motion may be very noticeable and intolerable. Regardless of the loads, though, the tires are wearing faster than they otherwise would and abnormal forces are being transferred to other structures which also may wear differently.

The same seems to be true for unstable knees. Even if the instability appears to be minimal and well controlled, the knee does not take favorably to being unstable. Wear and tear changes (by definition, this is arthritis) slowly begin to occur, such as increasingly roughened joint surfaces, damage to meniscus cartilages, and gradual stretching of some of the remaining normal ligaments which have to deal with greater loads.

Because of all of these factors, an "old" (chronic) ACL injured knee is generally looser and in poorer condition than a freshly tom (acute) one. Because of this, and depending obviously on the degree of looseness of the other ligaments and the amount of arthritis that has developed, reconstructing a chronic ACL knee is a very different proposition than reconstructing an acute ACL knee. The results are statistically different in virtually every study that has been done, even though the overwhelming majority of outcomes are a functionally stable knee.

Every patient with an ACL tear that is more than a few years old needs to have the knee carefully evaluated to determine what damage has occurred to all the structures besides the ACL. The surgeon and patient need to discuss the realistic expected outcomes in light of those factors. Still, generally speaking, reconstruction works very well in all but the most damaged chronic ACL knees in restoring stability and making the knee trustworthy again.

Pain and instability are two different things

One important thing to understand is that knee instability is painful only at the moment when the knee gives way. Sometimes an instability episode hurts a lot, and sometimes it is just uncomfortable. Typically, even with a painful instability episode, the painfulness dissipates quite rapidly, although some swelling in the knee afterwards (usually because of internal bleeding) may have some pain associated with it. Blood is an irritating substance when it is free in the tissues, and blood in the knee creates its own irritation and typical aching pain, but this is different from the sharp instantaneous pain when the actually knee buckles.

Pain which is constant, or lasts for days, or comes back over and over again, especially if it increases after exercise, is not characteristic of ligament instability. That type of pain pattern is much more typical of something else, maybe early arthritis or maybe a tom meniscus. A good diagnostician can usually sort this out by taking a careful and detailed history, and sometimes with the help of x-rays and/or MRI. Things can become more clouded if the ACL has been loose for a long time, and the knee has developed some arthritis. The key point to remember, though, is that restoring the stability of the ACL does just that – it restores a sense of stability. It does not solve the pain problem, if that pain pattern is not related specifically to instability episodes, and it is an error to think that having an ACL reconstruction will make a diffusely painful knee feel normal again.

Even a reconstructed knee is not normal

Although it has not been studied sufficiently well to say for sure, it appears that even a well reconstructed knee is vulnerable to developing arthritis at a faster rate than a normal knee. To study this well would require looking at large number of patients (maybe 100) who each had perfectly normal knees to start with, and who have no other predisposing factors for arthritis (malalignment, genetics, other previous injuries, etc.). All of these patients would need to have injuries of identical severity (i.e., just the ACL tom with no associated meniscus tears or damage to the joint surfaces or underlying bone). Each would then have to have their knee reconstructed using the exact same technique and would have to be rehabilitated in the same way, and then followed over 10-15 years using the exact same monitoring techniques. Finally, the activity level of these patients and re-injury history would have to be essentially the same over the 10-15 years study period. Only then could the outcomes of this group of patients be compared legitimately to a similar group of uninjured patients, identically matched for age, size, predisposing factors, injury history, and activity level. Any differences might then be attributed to the reconstructed ACL.

This kind of valid comparison study has not be done, and may never get done due to the cost and complexity of accomplishing it, but a few preliminary studies, without all the controls, seem to point toward more arthritis in reconstructed knees than in the opposite uninjured knees. On the one hand this is disappointing news for anyone who has an injured ACL, but on the other hand, there are other things that may matter more to the person with a tom ACL than the likelihood of getting some degree of arthritis in their knee many years later.

A matter of function - and lifestyle

The ultimate deciding factor for most patients with tom ACL's is what reconstruction can do for their ability to function, particularly in an athletic environment. What ACL reconstruction does well, and very reliably, is to restore stability to the knee. Reconstructed knees are reliable and stable. They don't give out unexpectedly, and they allow their owners to return to vigorous athletic activities usually without any compromises. Many, many reliable studies show that 80-90% of patients return to their pre-injury level of activities, without any significant negative symptoms. For the competitive athlete, this can be extremely important. In some cases it is even a matter of earning a living or funding a college education.

Advancement in the techniques for ACL reconstruction over the last 10 years, a decrease in the pain and temporary disability of the procedure itself (now often done as an outpatient), and a marked decrease in the time and difficulty of rehabilitation have all made the process much less intimidating for the patient. During the same time period, these advancements have also made the results more predictable and the complications less common and less severe.

For the competitive athlete, or the recreational one, a tom ACL is a significant threat to continuing those activities. Statistically, more than 65% will have problems to some degree with unpredictable re-injury episodes, and possible further damage to meniscus cartilage or joint surfaces. Reconstructing the ACL will usually produce a result that will be very nearly normal or close enough to normal that the patient will self-classify themselves as having an "excellent' or "good' result.

This does not mean that every patient is free of all symptoms or that all patients are satisfied with their results. Ten to 20% of patients after reconstruction will end up being classified as having a "fair" or "poor" result, usually because of persistent pain, swelling, and rarely, persistent sensations of instability. Clearly some patients, even after technically successful reconstruction, who have good stability of the knee when measured in the office setting , will still have some difficulties returning to their previous level of athletic participation - usually because of discomfort or pain, persistent muscle weakness, swelling or other similar problems associated only with heavy or very vigorous use.

What it often boils down to

In the patient with a recent acute ACL injury, reconstruction offers an excellent chance of restoring normal or near normal stability of the knee, with no known increase in the risk of re-injury. The chances that this person will be able to return to their normal level of activities after a 6-8 month period of recovery are as high as 80-90%. The risk of serious complications are very rare, and most of the post-op problems that patients complain about are annoying, like swelling and discomfort with heavy use.

In my experience, the vast majority of patients who are active athletically or who want to be, given all the alternatives, will choose to have their ACL's reconstructed, and are satisfied with the results. Like any reconstructive surgical procedure, however there are real risks - in the 10-20% range - that there will be a less than perfect outcome. Unfortunately, it is impossible to tell ahead of time who will get what kind of result.

In my experience, though, certain factors do appear to correlate with better outcomes. Patients who are fit and athletic in their lifestyles, and who have a reasonably high pain threshold (which helps them during the early recovery and rehab period), and who are familiar with and comfortable with working out and doing the kind of exercises that they will need to do during the recovery period, generally recover more quickly and with less trouble - but not sooner than the 6 months that is required for the tissues to completely heal and regain appropriate strength, and for the essential protective muscle strength and reflexes to return.

Also, in general, reconstructing an acutely injured ACL - especially one with no concurrent damage to meniscus cartilages or joint surfaces (we call this an "isolated" ACL tear) - seems to have better results than reconstructing a knee with years of instability -especially if those knees also have tom meniscus cartilage or surface damage.

Patients who are older (how old is old is always an issue!) and people who are less fit or less athletically inclined are the patients where the most debate about doing a reconstruction should and does occur. Generally, if the instability is severe, and the knee is constantly buckling, the decision is clearer, and the resulting restoration of stability - even if no athletic activities are involved - is most beneficial to the patient. This kind of patient is usually very happy with the reconstruction.

On the other hand, if trying to get along with a little instability, which can be largely controlled by avoiding some activities that the patient doesn't really mind avoiding, then going the "conservative" route and avoiding surgery is often a very good choice - and many patients are happy with it. Certainly, there are many older athletes who are willing to avoid basketball, soccer, or racquetball, and stick to jogging or biking for fitness, and as long as their knees are stable and pain free for these activities they are happy.

For those people who choose not to have surgery, this does not mean no treatment at all. There is still a treatment program to be followed emphasizing muscle strengthening and learning to control the knee better and to avoid those situations most likely to cause instability. Many people benefit from this kind of rehabilitation. In general, stronger and fitter is better - and this applies to operated and non-operated knees equally.

Bracing of unstable knees and reconstructed knees has been traditionally thought of as beneficial. Unfortunately, the benefit appears to be more limited when looked at carefully and under strict testing conditions in the lab. Virtually all braces fail to control the critical 3-5mm of motion that would be required to prevent a re-injury, and this is especially true at the higher limb velocities that occur during athletics. Still, some form of light bracing may offer patients some degree of enhanced stability, even if only through complex feedback mechanisms that the brain uses to help control the knee and the surrounding muscles. Overall, though, the routine use of braces to try to control knee stability is now felt to be inappropriate by most experts.

 Technique of ACL Reconstruction 

 Top of Page

Home | About | Physicians | Contact | Search | Legal