Quick and dirty review of anatomy for beginners

The knee is a complex joint that needs to move in many directions under weight-bearing loads. The bottom of the thighbone (femur) meets the top of the tibia, which is the larger and inner (medial) of our two lower leg bones (the other being the fibula, which sort of hangs out snuggled up to its larger sibling). Floating in front of them is an odd shield of bone, the kneecap (patella).

For the bones of a joint to stay in place relative to each other, and to keep us from collapsing in a heap, we need some support structures (connective tissue). The muscles of the leg are attached to the bones, so they can make them move, by tendons (I think of tendons as the strings on marionettes: by holding things in connection, they translate movement here into movement there). The bones themselves are connected to each other by ligaments (I think of ligaments as strapping or bindings). Finally, where bones meet, they need to be cushioned. There are, in some parts of the body, little separate sacs called bursae (think of the cells of a piece of bubble wrap, but with a fluid gel inside instead of air); the knee has these. And at their ends, the bones themselves have a layer of cartilage to absorb the wear and tear of daily life's movement-with-weight-bearing (quick, another analogy...ok, the little plastic gliders you tap onto the bottoms of table and chair legs; heck they even LOOK like cartilage!).

The bottom of the femur and the top of the tibia are indeed cartilage-clad. However, since the femur ends in two round knobs, and the top of the tibia is pretty flat, its not a great match and something extra is needed. That's the role of the medial (inner) meniscus and the lateral (outer) meniscus, a pair of horseshoe shaped cushioning cartilages that live between the femur and the tibia. A meniscus can be torn as the result of a sudden torquing movement, or as a result of repeating grinding.

There are large ligaments on the outsides of the femur and tibia that look and act very much as straps holding them together. The cruxiate ligaments provide extra support deep within the knee joint. They are paired, an anterior (front) cruxiate ligament and a posterior (rear) cruxiate ligament; they are called cruxiate because (ta-da!) they cross each other to form an "x" in between the femur and tibia. Like any ligaments, they are subject to either stretching minor sprain) or outright tearing. For some reason, at least anecdotally, aikidoka seem more prone to injury of the anterior cruxiate ligament (ACL)

What if my knee is injured?

The immediate first aid is the same as for any soft tissue injury: RICE. If your leg injury causes a feeling of instability at the knee, it may indicate ligament damage. A meniscus tear is sometimes accompanied by swelling, catching, and a "clunk" sound. A physical exam by a physician skilled with emergency, injury or sports medicine can assess overall joint function, tendon integrity, and joint stability, but will probably not give a 100% positive diagnosis. A "regular" x-ray will not show soft tissue damage. An MRI will (of course, like any test, it is not 100% perfect either).

If your doctor or insurer balks at doing an MRI, how much should you fuss? Well, if you go in for treatment, and have been ruled out for a broken bone by exam or x-ray but you can't really walk, I'd pretty much insist on getting some answers right away: It likely won't be an MRI on the spot, but either an appointment for one or an appointment asap with whomever can authorize one for you. Take a deep breath and resolve to be willing to get on the phone and be pleasantly persistent in order to get what you need.

If, on the other hand, the physician doesn't think that you have meniscus or ligament damage, and if you have decent weight-bearing ability and minimal swelling and pain, I might consider holding off for a couple of weeks to see if this is something that might heal with "tincture of time" (for instance, a muscle injury that might show improvement within a week or 2 and be nicely healed in a couple of months). However, that time must be spent truly promoting healing: RICE, no activities that put you at risk for re-injury, etc. If there is not significant improvement, then I'd do whatever it takes to get an MRI and a consult with a qualified sports medicine physician. You only have one body and two knees, and no matter how compliant a patient you are, cartilage and ligament tears will not self-repair!

A word about braces: The over-the-counter elastic-based supports may provide a nice snug feeling and add some warming to the joint, and they are very good at providing the "C" (compression) part of RICE. They cannot actually give support to an unstable joint. Do not be lulled into a false sense of security and start training with one thinking it will protect you. It won't.

Having said that, there ARE custom-fitted braces available by prescription that will provide some stability. Ask if your benefits coverage includes durable medical equipment, and if your provider will authorize it.

A little bit about knee repairs, based on a review of articles and a long chat with the doctor...

Arthroscopy is one of those "band-aid" same day procedures. It can be done under a local, with or without (yeah, right...) sedation, or with a spinal anaesthetic, or if you are really nuts, under a general anaesthetic. What do they do once they are in there?....It depends. Since the MRI is not 100% definitive, nobody really knows what's going on until they get in there to look.

A meniscus tear can be handled in a couple of ways. You can opt not to treat it. Frankly, I don't think this is a good idea. It will result in altered body mechanics in the knee joint, which will cause the meniscus to be further ground away; when its gone, the only place for wear and tear is the cartilage at the end of the bones, when that's gone...well, you get the idea.

The damaged parts can be removed (partial meniscectomy) or, if the whole thing is in pieces, the meniscus can be removed altogether (total meniscectomy). The good side: minimal recovery time (some people go back to work in a couple of days). The bad side: Cartilage once lost is gone.

Some tears, depending on where/how, are repairable, most often by suturing. The good side: a repair that hopefully will hold up with time. The bad side: longer recovery time than with scraping/removal (I was told it could be a couple of weeks; your mileage may vary...). For younger, more active people, repair is definitely considered preferable to removal.

While they are in there, they can look at the cruxiate ligaments and a decision can be made regarding what to do. If the ligament is not torn, but is stretched, there is a fairly new procedure called thermal shrinking. Heat is applied to disrupt hydrogen bonds and shrink the collagen fibers; it requires the right balance of heat and time, and there are a couple of ways of doing it (laser and radiofrequency). From a review of articles, it appears to be effective, but the effects are variable and not predictable. It will definitely cause a short term weakening of the tissues, during which time they can actually be stretched further (hence a few weeks of bracing and non-weight-bearing followed by rehab).

What about repairing a torn ligament?

Oy. Now we're talking the big deal, major rehab process. The ligament has to be replaced with something that will attach to the femur, attach to the tibia, have some give but not too much, and withstand all kinds of forces from all kinds of directions (note that most objects in nature fall into one of two categories: stretch-instead-of-breaking versus break-instead-of-stretching. We, of course, want ligaments that just hold tight no matter what darn fool thing we ask of them).

One way to form a new ligament is to take a tendon from another part of your own leg (autograft). Some doctors like to use patellar tendons and some use hamstrings tendons. More recently some have been doing tendon transplants from folks who don't need them anymore (allograft). All three have their own risks and benefits.

The big advantage of your own tissue is, well, it's you. Your body will accept it easily. Another advantage is that the autograft tendons seem to hold up longer without stretching. However there is more pain and a greater risk of infection because of having to essentially do two surgeries. The rehab process is harder and takes longer: first, you have a donor site that has been cut, disrupted, and then put back together and now has to heal; second, you can't remove a tendon without some alteration in structure and function of the affected part.

The allograft method is newer and shows promise in that it is a shorter surgery, with less pain, a lower infection rate, and a shorter rehab time. Anytime one takes another's body parts, there is a risk of infection (AIDS, hepatitis) and rejection. Current screening tests appear to be effective for identifying disease-carrying tissue; no cases of transmission have been identified. Rejection of a tendon is very rare, as compared to of a heart or kidney, because there are not a lot of antigenic proteins on connective tissue, but it can happen. If it does, the graft has to be removed. A key disadvantage is that the allograft seems to be a somewhat looser and less strong graft than the autograft.

I don't think there is any one "right" choice. These are judgement calls; each patient needs to review the literature and talk with his/her surgeon. If you talk with friends or check out the online chat rooms or bulletin boards, beware of making a final decision based on one or two compelling anecdotes. What I've learned in 20 years as a nurse is that for ANY given medical procedure there will be both horror stories and miracle stories. If I needed a repair, I'd probably opt for the allograft, trading off a potentially weaker graft (ok, so I wear a brace in the dojo from now on...) for not having to be so worried about problems with the donor site.

Janet