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Meniscus injuries of the knee – commonly meniscus tears or meniscus strains – are common among both athletes and non-athletes. A meniscus injury or a lack of a meniscus can lead to osteoarthritis.
The knee joint has two menisci that function as important shock absorbers to the knee to prevent joint overload:
In the form of a C-shape, the meniscus is wedged between the femur (thigh bone) and tibia (shinbone) to help maintain balance and stability. In other words, the menisci help distribute the weight of the body appropriately across the knee joint. Without the meniscus, an uneven weight distribution would occur leading to overload of the cartilage surfaces.
A meniscus injury can occur by way of tears and strains, some of these injuries are mild and can be treated conservatively, while others are serious and will require surgical intervention. Typically, a torn meniscus is caused by twisting or turning quickly, often with the foot planted while the knee is bent. Meniscus injuries are most commonly seen in soccer, football, basketball and skiing,
When the meniscus is torn, the patient may feel a “pop” in the knee. In most cases patients can still walk, and some athletes can continue playing with a torn meniscus. Gradually, the knee will become more stiff and swollen over the course of several hours to days.
The most important thing to determine when there is a meniscus tear is if it was preexisting or if it is a new tear. Preexisting tears may be stable and degenerative and may not need surgery. However, with an acute injury where there is associated pain, especially at the joint line, one has to be concerned about a possible meniscus tear. Signs of a meniscus tear can include:
There are multiple other scenarios that can be present for meniscus tears, but these are one of the most common that present to us for evaluation.
The exact treatment method will depend on the size, location, and type of tear. The patient’s age, history of injury, and activity level will also determine the treatment method. The outside one-third of the meniscus has a rich blood supply, known as the “red zone”, this portion of the meniscus may heal on its own if the tear is small. The inner two-thirds of the meniscus has a lack of blood supply, known as the “white zone”. This portion of the meniscus cannot heal on its own.
For surgical treatment Dr. LaPrade will use knee arthroscopy to either repair the meniscus or to trim out those portions which cannot be repaired
The ability for a meniscus to heal itself depends upon where the tear is located and the underlying blood supply that goes to that portion of the meniscus. Meniscus tears that are at the attachment site of the meniscus to the capsule, called meniscocapsular injuries, have a good healing potential if they are smaller tears and will not displace. Meniscus tears in the thinner portion of the meniscus, located more deeper within the center of the joint, have a much lower chance of healing and often do not heal at all.
Meniscal injuries can be difficult to assess because sometimes the patient’s history does not fit with a meniscus tear or because direct palpation of the joint line may not be possible in heavier patients. In addition, MRI scans are not always 100% accurate in terms of diagnosing a potential meniscus tear, so the gold standard of diagnosing a meniscus tear is an arthroscopy and direct palpation of the meniscus itself with a surgical probe.
Meniscus tears may occur without swelling. In these circumstances, a flap of meniscus may catch inside the joint and cause significant pain, but may not have a lot of bleeding which could lead to swelling. In addition, preexisting meniscus tears that tear a bit further, such as degenerative meniscus tears that tear more with a twisting, turning, or pivoting injury, may not have a lot of swelling.
Part of the best way to differentiate between a medial meniscus tear and an MCL tear is based on the clinical exam. In thinner patients, we can usually palpate directly over the MCL and differentiate if that is the portion that is injured. Tissues in front of it and back of the MCL can also be palpated directly to best assess if there is an underlying meniscus problem. However, sometimes, medial meniscus tears do occur with an MCL tear, so a careful assessment must be matched with an MRI scan to determine the injury combination present.
Standing x-rays are useful to help determine the potential treatment for a meniscus tear. This is because if there is significant joint space narrowing and bone spurs, which indicate a significant amount of arthritis, then a surgical treatment would possibly not be indicated for a meniscus tear. However, if the joint spaces look entirely normal and there is a meniscus tear, we would be more likely to look at repairing the meniscus or working it up further to try to preserve the normal cartilage surfaces.
There are some meniscus tears that could be potentially stable and treated without surgery. These include degenerative tears of the posterior horn of the medial meniscus, which are asymptomatic. In these tears, there may be a split of the meniscus, which does not fold upon itself and does not cause any associated pain. These types of meniscus tears may be an incidental finding upon an MRI scan for another pathology that is suspected within the knee. In addition, in older patients that do have meniscus tears that do not cause any mechanical symptoms or pain, observation rather than surgical treatment may be indicated.
Meniscus tears can certainly occur with squatting, especially as we get older. In particular, a posterior horn medial meniscus root tear can occur with deep squatting such as when gardening, carpet laying, plumbing, or other activities which require deep squatting.
There is really no upper age limit for when a meniscus tear should be repaired, rather one has to look at multiple factors, including the patient’s activity level, the amount of underlying arthritis, and if there are other injuries present. In general, saving the meniscus is definitely preferred over taking the meniscus out. This is because removing the meniscus, even small amounts, significantly increases the risk that one will develop osteoarthritis. Therefore, in young patients we try to stretch the limits to perform meniscus repairs to try to save their cartilage, whereas in older patients who may have meniscus tears that are definitely able to be repaired, we proceed with repairs to try to prevent any arthritic changes.
The typical meniscus does not have a good blood supply, so it has a dark contrast signal throughout. If there is a white line within it, this can indicate a tear. A grade 1 MRI finding would be a small tear within the middle of the meniscus that does not go to the joint surface. A grade 2 MRI signal would indicate a larger line which goes close to you, but not up to, the surface of the meniscus. A grade 3 MRI meniscus signal would indicate a tear that could be seen and probed surgically. These would be defined as tears whereas the other 2 would be intrasubstance changes within the meniscus clinically.
The main physical examination points for a meniscus tear depend upon whether there are other associated injuries. In general, we want to make sure that the patient’s knee motion is full after an injury because an inability to straighten the knee or fully bend the knee may indicate a meniscus tear is present. In addition, we assess for pain directly along the joint line, which may be directly located where the meniscus tear is present. In addition, pain in the back of one’s knee with squatting or with the examiner pushing their knee into full flexion may indicate a meniscus tear. Other times to think about a meniscus tear is when one is evaluating an ACL or PCL tear and there is extra motion present than one would expect with just an ACL or PCL tear, one has to be concerned that possibly there is a meniscocapsular or a meniscal root tear associated with the cruciate ligament tear.
There are 2 types of meniscus tears that we commonly see in the NHL. One of these is a bucket-handle tear, which happens from a player catching their skate in a crack in the ice and twisting their knee significantly. In this mechanism, the meniscus can tear from the back and flip to the front of the knee, similar to how a bucket-handle moves in a bucket. The treatment for these would be to put them back in place and sew them around the edges. Other types of meniscus tears that we see are associated with an ACL tear whereby the meniscus tears away from the joint lining. Sometimes these tears can be quite large and need to be repaired. When there is a split of the meniscus, called a radial tear, we also try to repair these in NHL players. This tear ends up with a much slower rehabilitation program, but we do know that for most professional athletes, removing the meniscus shortens their career so we try to repair them in these circumstances.
For NFL athletes, we have definitive information. For athletes who have the meniscus removed, they have further progression of arthritis and their careers are shortened. For athletes who have their menisci repaired, they do not seem to have any further progression of arthritis and their career is not shortened. Thus, while the quicker treatment may be to take the meniscus out and get the athlete back playing sooner, proceeding with a meniscus repair is in the athlete’s best interest over the long term because it should extend their career and also allow them to have a healthy lifestyle once they are no longer playing professionally.
The most common cause of a locked knee with a meniscus tear is a bucket-handle tear of the meniscus. This is where the meniscus tears away from the joint lining and flips like a bucket-handle and gets stuck in the front of the knee instead of being in its normal position in the back of the knee. Other types of locking of the meniscus can include flaps of the meniscus, which can get pinched inside the joint, whereby one feels like they are walking with a pebble in the shoe and they cannot put full weight on their knee.
Most meniscus repairs occur in the middle to back part of the meniscus. In these locations, the more one squats down, the more weight that is put on the back of the knee. Thus, we generally avoid squatting, squatting and lifting, and also sitting cross-legged for 4 months after meniscus repairs to avoid overstressing the area where the meniscus was sutured.
Not all meniscus tears are the same, so the recovery time for meniscus repairs will not be the same either. In general, if there are no other injuries other than the meniscus repair, peripheral repairs of the meniscus take about 4 months to return to full competition. Radial repairs and root repairs take 6-7 months to return back to competition because these repairs have a poor blood supply and are more “fragile.” Tears like horizontal repairs, complex repairs with fibrin clot interposition, or oblique repairs would have a similar return on the timeframe as root and radial repairs.
When one does hyperextend their knee, especially when it is loaded, it could pinch the anterior horn of their menisci and potentially cause a tear. In most circumstances, I have seen this with a lateral meniscus anterior horn tear. In general, these types of tears we would try to repair if possible because the lateral meniscus is so important at preventing arthritis.
Because of the violent nature in deep squatting in many CrossFit activities, we see many people who do tear their menisci in CrossFit activities. The most common types of tears include tears in the back of the menisci, which can include root tears. Therefore, older patients who participate in CrossFit should be aware of this and avoid going to maximal flexion with deep weights because it could tear their menisci.
Most meniscus tears that occur in basketball players are associated with other ligament tears. Therefore, if they tear their ACL with a noncontact mechanism where they plant and twist, they can also tear the posterior horn of their medial meniscus. Due to the effects on one’s career, we generally recommend repairing these types of meniscus tears, even if they occur without any other ligament pathology, to ensure that one has the longest career rather than returning them to competition sooner.