What is the meniscus?
The meniscus is a somewhat semicircular structure that is attached to the top of the tibia (shin bone) and serves as a cushion between the femur (thigh bone) and tibia (shin bone). The meniscus provides many functions within the knee, but most all of those functions relate to protecting the articular cartilage (cartilage on the end of the bone). When the articular cartilage is significantly damaged one has the condition that would commonly be called degenerative arthritis. So when possible, particularly in young patients, keeping the menisci are very important for ultimate knee function.
How is the meniscus injured?
The meniscus can be injured with an acute (sudden) twist or injury of the knee. Sometimes this is associated with an injury to one of the ligaments at the same time. Other times it can be a more simple injury such as just being in a squatted position and twisting the knee or moving to stand up. In other patients no specific injury can be pinpointed and the patient just notes progressive onset of pain with perhaps some swelling over time.
What are the symptoms of a meniscal tear?
Most patients present with fairly localized pain to either the medial (inside) or lateral (outside) of the knee joint itself. They can typically localize this pain with just a fingertip. It is not so common to have a meniscal tear give global, or diffuse knee pain. Patients will frequently get some mild swelling in the knee. Commonly there are some mechanical type symptoms such as a specific catch or pop. At times patients can describe locking in the knee. True locking in this sense is an inability for the patient to straighten the knee, NOT an inability to bend the knee. Symptoms can come and go and at times be confusing for a patient since one day they can function very normally and another day they may feel very limited.
How does a meniscus tear get diagnosed?
In many circumstances the history and physical examination of a patient are so specific for meniscal tear that an orthopaedic surgeon may need little other information in order to be able to make a diagnosis of the meniscus tear. Typically x-rays are performed in order to evaluate for arthritis, loose pieces in the knee, overall alignment of the leg, and other specific possible diagnoses. In settings where radiographs, history, and physical do not clearly point to a meniscus tear, the orthopaedic surgeon may consider getting an MRI for confirmation. Although not 100%, MRIs are very accurate in being able to diagnose meniscal tears. It needs to be clear, however, that meniscal tears are not always the cause of a patient’s symptoms. It is not that uncommon that a patient has significant arthritis and perhaps other associated factors such as abnormal limb (leg) alignment or being overweight. Although an MRI might show a meniscal tear a large aspect of the patient’s symptoms may well relate more clearly to these other issues. Therefore, meniscal surgery may not result in good symptom relief in some of these patients.
Meniscal tears are routinely managed by arthroscopy. This is placing a small microscope into the knee and using small specialized instruments to deal with the meniscus tear. During this time the patient typically is under a general anesthetic. Frayed and torn meniscal fragments are removed, but as much of the normal rim of the meniscus is kept in place to maintain as much function as possible. There are circumstances, most commonly seen with associated ligament injuries, when the meniscus can be repaired. In this setting the meniscus itself appears fairly normal, but it has been separated from the surrounding attachment to the knee. In this setting, the meniscus can be sutured back to the periphery in order to get the meniscus to heal. The purpose of this is to maintain meniscal function for the future and minimize chances for arthritis. It should be noted that the majority of tears are not amenable to this type of repair treatment. Most are fragmented and split in a way that the meniscus will not heal and so the offending pieces need to be removed. All of these procedures are done as an outpatient.
Some menisci can be repaired:
What is the recovery and rehabilitation after meniscal surgery?
With simple arthroscopy and removal of a piece of meniscus the recovery is very rapid. Patients do not need to use crutches or braces. They start on motion immediately and within days are walking pretty normally. Most patients can return to normal activity in a few days to 3 to 4 weeks. Many patients, after surgery, can do their own rehabilitation by getting on an exercise bike, for example, but some patients are slower or have more swelling and pain, and formal physical therapy may be considered. In the case of a repair, when the meniscus is sutured back in place, the surgeon may ask the patient to use crutches and/or a brace for up to 6 weeks. Because the healing process can be slow with a repair, patients would not return to twisting, cutting, or jumping type of sports typically for a minimum of 4 months.
There are times when damage to a meniscus is to such an extent that it cannot be repaired or repair has failed and a patient is left with minimal to no meniscal cushion present in the knee. For some patients the loss of a meniscus can be a source of pain. Meniscus loss can also be an issue with significant instability of the knee. In very select cases meniscus transplantation can be considered.
What is meniscus transplantation?
Meniscus transplantation is where an appropriately sized meniscus from a cadaver donor, much like with a heart or kidney, is selected and implanted in the patient’s knee. This does not produce any kind of significant rejection phenomenon and patients do not need to take any kind of special drugs or medicines when this is done. There is the tiny risk of the potential for disease transmission with meniscal tissues, and these implications should be discussed with the surgeon.
What patients may be indicated for meniscus transplant?
This is a very complex question and involves many factors. The articular cartilage needs to be fairly normal. Significant wear or arthritis makes it so meniscus transplantation is not advised. The patient’s knee needs to be stable so that if there are significant ligament issues these need to be addressed prior to, or in addition to, meniscus transplantation. Leg alignment is important in that some people have significant bow legs or knock knees, and this can play a role in successful meniscus transplantation and needs to be evaluated. Age of the patient is a factor in that as patients get older other options may become more reasonable and predictable to solve pain problems. The patient expectations also need to be considered. Meniscus transplantation really shouldn’t be viewed as a replacement for a meniscus that was removed and then return to full high end competitive athletics or stressful activity. It is really more intended to help with routine daily activities and light recreation. A patient has to be aware of the limitations of what meniscus transplantation can do to return them to a normal situation. There are other patient related factors such as obesity. Someone who might be a reasonable candidate for meniscus transplantation but is significantly overweight would perhaps be better served by losing that weight to see if that helped with symptoms prior to consideration of meniscus transplantation. There are many other factors in this decision making process and they should be discussed with the surgeon.
How is a meniscus transplantation performed?
The patient usually has x-rays to size the anticipated meniscus and a company that deals with obtaining meniscal tissue is contacted. When an appropriate size is available this would then be shipped to the patient’s hospital. The patient then comes in and has a combined arthroscopic and open procedure to implant the meniscus with its attached bone. This typically takes a couple of hours. The patient, depending on certain circumstances, could potentially be done as an outpatient, but at other times will spend a night in the hospital.
What about anesthesia?
Typically patients get a general anesthetic for this surgery and at our facility we also use nerve blocks to help minimize any early postoperative pain.
What about risks and complications?
Meniscus transplantations are a reasonably significant operation and so there are several potential problems. First of all, the meniscus has to be sized accurately and a meniscus that is too small or too large may fail. Because the patient has functioned without this meniscus for a long time sometimes regaining absolutely full motion can be a problem since the knee gets a little “tighter”. Obviously, as with other surgeries complications such as infection, blood clots in the leg, etc. can also appear. For a complete list of complications the surgeon should be consulted.
What is the recovery from meniscal transplantation?
Typically immediate motion is started. Patients are typically kept on crutches for a period of 4 weeks or so allowing the meniscus to heal so that it can withstand the stress of weightbearing. It probably takes 3 to 6 months to get back to normal activity on the meniscus and return to recreational activities.
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