The menisci — the medial meniscus and lateral meniscus - are crescent-shaped bands of thick, rubbery cartilage attached to the shinbone (tibia). The meniscus functions to improve the fit between the femur and the tibia, to absorb shock, stabilize the knee and distribute load in the knee, and to help move lubricating fluid around the knee
The medial meniscus is on the inner side of the knee joint.
The lateral meniscus is on the outside of the knee.
Meniscus injury can vary widely in size and severity. A meniscus can be split in half, ripped around its circumference in the shape of a C or left hanging by a thread to the knee joint. A barely noticeable tear may resurface years later, triggered by something as simple as tripping over a step.
The medial meniscus is an important shock absorber on the inside (medial) aspect of the knee joint. It absorbs about 50% of the shock of the medial compartment. Thus, when there is a medial knee injury such as a medial meniscus tear, it is very important to try to repair the tear, because if not repaired and is trimmed out there will be an increase to the load on the medial compartment, which ultimately leads to osteoarthritis.
A medial meniscus tear is more common than a lateral meniscus tear, because it is firmly attached to the deep medial collateral ligament and the joint capsule. In addition, the medial meniscus absorbs up to 50% of the shock of the medial compartment, making the medial meniscus susceptible to injury.
A complex tear of the medial meniscus includes a combination of any of the patterns listed above.
The lateral meniscus is an essential shock absorber on the outside (lateral) aspect of the knee joint. It absorbs about 70% of the shock of the lateral compartment. Lateral meniscal tears are not as common as medial meniscus tears. This is because the lateral meniscus is more mobile and not secured as much to the lateral tibial plateau as the medial meniscus is to the medial tibial plateau. Thus, when there is a lateral knee injury such as a lateral meniscus tear, it is very important to try to repair the tear, because if not repaired and is trimmed out there will be an increase to the load on the lateral compartment, which ultimately leads to osteoarthritis.
When determining the treatment for a meniscal tear, the orthopaedic surgeon will consider the following factors:
When the injury happened
Injury symptoms
Any other associated injuries
After considering these factors the doctor will choose to treat the injury non-operatively or surgically.
Many small meniscal tears will heal without surgical treatment. Also, some tears may have no symptoms and in other tears, symptoms may eventually disappear. Partial tears, degenerative tears, and stable tears may be observed for 2 - 3 months. If symptoms disappear, no surgery is needed. The use of a knee brace and restriction of activities may be recommended to prevent further injury.
In many circumstances in patients with these tears, the meniscus needs to be trimmed out. However, this does increase the risk of osteoarthritis, especially in patients who continue to participate in impact activities.
Research has justified that patients with a certain age, with a proper environment, fairly normal articular cartilage, and neutral or near normal alignment, should have an attempt at a repair for meniscus tears.
Both the medial and lateral menisci have a stout attachment at their very posterior aspects, which are called the root attachments. These root attachments are important because they hold the meniscus in place, provides stability to the circumferential hoop fibers of the meniscus, and prevents meniscal extrusion.
When there is a tear of the meniscal root, it has been demonstrated on biomechanical testing that it is equivalent to having the whole meniscus removed. Thus, a tear of the meniscal root is considered a very serious condition.
There are two different group of patients who suffer meniscal root tears:
The first group consists of athletes in their 20s who sustain the tear with trauma. This could include an injury to the ACL, PCL, and other associated ligament combinations. In these circumstances, the meniscal root is commonly torn along with the ligament, and it is recommended to perform a concurrent meniscal root repair. Failure to repair the meniscal root tear in these circumstances can lead to the development of osteoarthritis, failure of a cruciate ligament reconstruction graft, and other problems further down the line.
The second group of patients who commonly tear their meniscal root is adults in their 50s. The consequences of a meniscal root tear appear to be much more severe in this age group. A meniscal root tear, which can occur with minor or seemingly trivial trauma, with a pop in the back of their knee with deep flexion, squatting and lifting, and other activities, can be quite severe. It is in this group of patients for which the rapid development of osteoarthritis can occur. In some of these patients, rather significant bone swelling, insufficiency fractures, and the appearance of osteonecrosis (avascular necrosis), can obscure one to seeing that it was caused by meniscal root tear.
The root attachments of the posterior horns of the medial and lateral meniscus are very important for joint health. When these are torn, the loading of the joint is equivalent to having no meniscus on the affected side. Thus, these patients can often have early onset arthritis, the development of bony edema, insufficiency fractures, and the failure of concurrent cruciate ligament reconstruction grafts. In particular, it has been found that one of the most common reasons why younger patients need total knee replacements is because of a neglected or undiagnosed meniscus root tear leading to the development of osteoarthritis.
Therefore, Dr Savadekar consider repairing the root tear to save the knee joint. A concurrent distal femoral or proximal tibial osteotomy may also be indicated if the patient is malaligned to unload the affected compartment.
A medial meniscus tear can happen from many factors. First, a sporting injury can cause it. Medial meniscus tears commonly happen with an ACL tear. This is because the medial meniscus acts as a secondary stabilizer to prevent the knee from slipping forward, and when the ACL tear happens, it puts extra stress on the medial meniscus which leads to it tearing. In addition, deep squats put extra stress on the back of the knee and can cause a medial meniscus tear to occur. Other causes include twisting, turning, or pivoting type activities where extra stress is placed on the inside of the knee, whereby a medial meniscus tear can occur
Most new onset, or acute, medial meniscus tears do cause pain. The pain is usually located along the inner portion of the joint, at the joint line, or in the back of the knee, especially when one squats down. Tears in the front part of the meniscus are less rare, but these can cause problems going down hills or down stairs. Longstanding meniscus tears, or chronic tears, may or may not cause symptoms. Usually when they do cause symptoms, people will notice them when they have possibly a further tear of an underlying tear, and there will be pain along the joint line with squatting, twisting, turning, or kicking type maneuvers.
Most medial meniscus tears that occur in athletes occur due to contact or noncontact twisting mechanisms. A large majority of these occur with a concurrent anterior cruciate ligament tear, where the joint slips forward with an ACL tear commonly results in tears the meniscus away from its attachment at the joint lining. Other types of tears in athletes can occur with significant stresses, or with activities that results in deep-knee flexion, such as a hyperflexion injury while skiing or while playing football.
There are some types of meniscus tears that could potentially heal themselves. They depend upon the type of meniscus tear and the location of the tear in the joint. If the meniscus is torn at the edge where it attaches to the joint lining and the tear is small, there is the possibility this could heal. In addition, there have been occasional case reports that report that some radial tears may heal over time, although this is not expected for the vast majority of tears. What it does indicate is that the meniscus does have some ability to heal, so pushing the limits for a repair, especially in a young patient, would be indicated.
In general, a lateral meniscus tear should cause pain along the joint line of the outside part of the knee. In addition, one could have pain in the back of their knee with deep squats or they could have pain on the outside of their knee when they put their leg in a figure-of-4 position. These are the usual locations that a lateral meniscus tear will hurt.
It is hard to differentiate what type of tear is worse if it is repairable. However, it is well known that if a lateral meniscus is taken out, the consequences are almost always worse than having a medial meniscus resected.
In general, because of the important shock-absorbing ability of the meniscus, repairable lateral meniscus tears should have an attempt at a repair as long as the patient is fairly active and does not have any significant arthritis. For smaller tears or tears that are in an area with hardly any blood supply, a trimming would possibly be indicated. This would be called a partial meniscectomy.
One of the most common causes of locking with a meniscus tear are either a tear that has torn at the edge and slips into the joint with twisting and turning or a meniscus that totally flipped from the back to the front, called a bucket-handle tear, which can block extension. Many athletes that are seen that do present with a a bucket-handle tear had a previous history of catching or locking with activities that was a prelude to having the entire meniscus flip upon itself.
The meniscus root is where the main body of the meniscus attaches to the bone. There are meniscal root attachments both in the front and back of the tibia.
A meniscus root tear happens when the root attachment is torn or destabilized. Most meniscus root tears actually are not the root tearing, but actually a tear of the meniscus within 1 cm of the root. These are called radial root tears and are about 90% of all meniscal root tears. A meniscus root tear can totally destabilize the shock absorbing function of the meniscus and can lead to insufficiency fractures, spontaneous osteonecrosis of the knee (SONK) and early onset arthritis in patients.
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