Dear Abe,
Your description of your most-recent injury event (i.e. an awkward fall after trying to jump into a squat from being seated crosslegged) paints a picture of meniscal tearing ("outside of my knee is being pushed inwards causing my knee to grind and shift out of place" and "bending and extending it almost like it is popping out of place" and also "it returns back to its normal position once over this one spot in my knee") combined with ACL re-injury ("I felt my knee shift a bit and it gave out with me falling to my side"). Please keep in mind that other structures can be injured as well, for example the MCL or LCL, or possibly even the PCL. It all depends on the types of abnormal forcing the knee was subjected to.
You noted that, within the past seven years, you have had two ACL reconstructions. This is in addition to two surgeries (within the past 3 years) to remove meniscal tissue. As you are likely already aware, each and every giving-way incident (including ACL injury or ACL reinjury or any instability manifestation) of the knee is likely to bring further damage that will move the knee closer to premature osteoarthritis. I also note that any loss of meniscal tissue will also predispose the knee to premature osteoarthritis.
Cases involving repeated ACL-graft failures and/or repeated meniscal injuries are always extremely complex, and this is even more so given that you have meniscal tearing as well. I asked Sue Barber-Westin, a clinical knee researcher with many years of experience, for her thoughts.
Sue noted that the first priority is to find out what caused the ACL-graft failures. Please keep in mind that this is not as easy as it might at first seem: an ACL graft can fail for more than one reason, and the reasons may be intertwined. But the most common cause of ACL-graft failure is surgeon error: that is, incorrectly placed bone tunnels.
Sue emphasized that the risk of ACL-graft failure increases with each surgery, largely because of the difficulty of getting an ACL graft to ligamentize properly in a bone that has been drilled too many times. Essentially, each time a graft is installed, the bone must be re-drilled, and eventually the ends of the tibia and femur begin to look like Swiss cheese on an X-ray view. Such bone is known as osteopenic, but the problem can be dealt with by careful bone-grafting in advance of the drilling of new tunnels.
Sue noted that a lack of revascularization of an ACL graft can be due to a number of causes, of which incorrectly placed bone tunnel is only one possibility. For example, poor-quality graft anchorage (i.e. anchoring the graft only at the ends furthest from the joint) can result in the now-notorious "bungee-cord effect", whereby normal physiological loadings on the inherently slightly elastic ACL graft (as part of the normal ramping-up of demands during ACL-surgery rehabilitation) result in it moving slightly inside the bone tunnel. This can ultimately result in a nonligamentized-and-stretched-out ACL graft, thus bringing a future predisposition either to sudden rupture or to gradually increasing instability that results in the injury of other structures (such as a meniscus, as you are already aware). Interference screws, the gold standard for ACL-graft anchorage, are still the safest bet (particularly if combined with the gold-standard ACL graft: patellar-tendon autografting).
Sue also pointed out that repeated ACL-graft failures can be due to overlooked deficiencies in the posterolateral-corner (includes the LCL) and the MCL. Bowleggedness or knock-kneedness can also increase the risk of ACL-graft failure. So can overly lax ligaments (e.g. knees which naturally hyperextend grotesquely). Poor-quality rehabilitation, insufficient rehabilitation, or simply doing too much too soon, are also common failure causes.
ACL reinjury can also occur from planting-and-twisting injuries (which may have been how you tore your ACL in the first place), as well as forced hyperextension and sideways forcing. To deal with the twisting-type injury concern (which can arise in daily living too), I strongly recommend you learn to pivot on only the front portion of your foot (i.e. avoid planting your entire shoe sole). This sounds simple, but it takes practice to make it an automatic habit. Other knee-injury-prevention exercises are available as part of a knee-injury-prevention training program. (Such programs were originally marketed towards female athletes, given that females have a higher ACL-injury risk than males. But now it is clear that these exact same programs are very valuable for male athletes as well. As an added bonus, these training programs result in improved athletic performance. However, keep in mind that such training is only something to consider after your have had your ACL re-revision reconstruction and have completed the formal phases of the rehabilitation, and only after both your surgeon and physiotherapist agree that your knee is ready for such demands...and as I will note later, it is possible that you will be advised to permanently refrain from partaking in knee-intensive sports.)
Meanwhile, injurious hyperextension and sideways forcing are very difficult to avoid in contact-type sports. The only reliable way to protect a knee from such forcing is to wear a suitably designed and properly fitted knee brace that places a hinged strut on each side of the knee. Such braces should be made of carbon-fibre composite for maximum strength at minimum weight, and ideally are custom-fabricated. Has your doctor ever mentioned such a brace? (Please remember that such a brace will not provide immunity to twisting-type injuries. You can only depend on such a brace to protect against injurious hyperextension and sideways forcing.) Even if you decide to avoid knee-demanding sports in the future, a high-quality functional knee brace might be extremely valuable if your employment takes you outdoors. The protective benefits of a good brace are highly desirable even if the knee is reconstructed and rehabilitated very successfully.
Another common ACL-graft failure cause is forgetting that no amount of muscle strengthening will accelerate the ligamentization process of the ACL. I note that the ACL graft is simply a pilfered sliver of dead tendon, and so it has no blood supply when installed. For an ACL graft to become a real, live surrogate ligament, blood vessels must first grow (vascularize) into the ligament, and then gradually the dead tendon tissue (which serves as scaffolding) is replaced by ligament cells. These cells develop the parallel-aligned collagen fibres that are the hallmark of ligament tissue...and in order for this to occur, they must be subjected to a gradual increase in stresses. Too much too soon will result in the graft either rupturing outright or gradually stretching out to the point of uselessness. Too little exercise will result in the graft merely becoming a useless mass of scar tissue. None of these ligamentization subprocesses can be accelerated by doing more exercises than what the rehabilitation protocol calls for.
Finally, it is also important to keep in mind that a reconstructed knee, irrespectively of how well it has been rehabilitated, will always retain a lingering vulnerability to future re-injury. One reason for this is that the reconstructed ACL often does not regain the tension-sensitive nerve endings that a natural ACL has. These nerve endings serve to keep the brain informed as to what is going on in the knee, thus enabling the brain to make optimal decisions with regards to how to avoid injury. These same nerve endings also serve to trigger the ACL-protective hamstring reflex. All these functions are compromised in an ACL-reconstructed knee. (Some nerve endings can regrow in a reconstructed knee, but there is still debate over how well these end up being connected to the brain. One goal of rehabilitation is to develop surrogate proprioception, whereby the brain learns to use information from other structures in the knee in its motor decision-making processes. Additional surrogate proprioception can be obtained by wearing a sleeve or brace on the knee. Medical-journal articles on these topics can be found in this forum's Knee Library.)
For these and other reasons, it is very wise to be extra-careful with any knee that has any history of ligament injuries or surgeries. Tricky twisting-type movements, such as trying to jump from a crosslegged seating position into a squat, are risky for never-injured knees...and extremely dangerous for reconstructed knees!
Also, please remember that injury severity is dictated primarily by kinetic energy (a staple topic in high-school physics, something which no one should graduate without). Kinetic energy increases with the square of speed, which means that if you do any knee-demanding movement three times as fast, your stopping distance will be nine times as great, and any injury will be nine times as bad. This is why running and changing direction rapidly (a cutting-type movement common in football, rugby, soccer and many other sports) is so knee-risky. The problem is magnified by the fact that moving faster means less time in which to react. (Incidentally, the exact same fundamental physical principles explain why speed is so often a factor in serious car crashes.)
Sue recommends that you have your knee examined by another orthopedist...and one who is highly experienced in complex knee situations. A surgeon who simply does first-time ACL reconstructions would not be a good choice here. You need a surgeon who not only does knee-ligament reconstructions, but who literally focuses his/her entire career on diagnosing and treating complex knee situations.
Sue noted that a third ACL reconstruction would still be appropriate for your knee, but the surgeon should warn you that even with no errors on the part of the surgeon, the risk of graft failure could be as high as 30% (simply on account of the aforementioned osteopenic bone and the resulting rise in potential for graft-vascularization problems). Sue also noted that, given the history of your knee, in any case it would not be recommended to plan on returning to high-risk, contact-type sports.
I would recommend you discuss your long-term plans (in terms of activities) with the knee-experienced orthopedic surgeon, and also with a knee-experienced physiotherapist. Meniscal transplantation would also be a good topic to discuss with a knee-experienced surgeon. I note that your meniscal-tissue loss is already severe enough that a seasoned surgeon would probably advise you to avoid all high-impact activities. Having a meniscal transplantation would give your knee a better chance of providing a reasonable number of arthritis-free years of service.
Please keep me posted with regards to your knee.
Yours truly,
Michael Frind.
Knee Library http://factotem.org/library
