- 1 How do you know if you have a torn meniscus in your knee?
- 1.1 Anatomy of the menisci
- 1.2 The mechanism of injury
- 1.3 Frequency of incidence
- 1.4 How does the patient present?
- 1.5 Doctor’s examination
- 1.6 Who is at risk of torn meniscus injuries?
- 1.7 How the diagnosis of a torn meniscus is confirmed?
- 1.8 An overview of treatment options
- 1.9 Treatment options for athletes with a meniscal injury
- 1.10 Surgical intervention in a torn meniscus
- 1.11 Rehabilitation and recovery time
How do you know if you have a torn meniscus in your knee?
An injury to the meniscus, which is a piece of cartilage that provides a cushion between the thighbone ‘femur’ and the shinbone ‘tibia’, requires a good understanding of its structure and function, and he factors involved in treating an athlete with non-operative or operative treatment. Based on the current knowledge of knee biomechanics, we will discuss everything related to torn menisci, from their anatomy to the possible treatment methods and modalities.
Understanding of the role of the menisci in the biomechanics of the knee has progressed steadily throughout the medical history. In 1968, Jackson wrote, “The exact function of that structure is still a matter of some conjecture.” As they have been well known to have an integral role in normal knee joint mechanics, nowadays, the menisci are not optional or expendable structures.
Anatomy of the menisci
The menisci are C-shaped structures composed of fibrocartilage, and they are located between the tibial plateau and femoral condyles. The medial meniscus is larger and semilunar compared to the more circular lateral meniscus. Both menisci have their anterior and posterior horns which are secured to the tibial plateaus. In the anterior side, there is a structure called the transverse ligament which connects the two menisci, whereas posteriorly, the meniscofemoral ligament stabilizes the posterior horn of the lateral meniscus to the femoral condyle. Additionally, the peripheral meniscal rim is loosely connected to the tibia via the coronary ligaments.
The joint capsule, which attaches to the entire periphery of both menisci, adheres more firmly to the medial one. When a compressive force is applied to the knee, the force is transmitted to the collagen fibers of the menisci which are arranged in a circumferential pattern. Since the blood supply to the menisci is limited to their peripheries, the peripheral rim of these menisci is so vital for their normal function and the potential to repair, that orthopedic surgeons tend to preserve the peripheral rim during ‘partial meniscectomy’ in order to avoid irreversible disruption of the structure. 20% decrease in the vascular supply by age 40 years was reported in a previous study, and this was attributed to weight bearing over time.
The mechanism of injury
The menisci are directly responsible for the transmission of forces, load distribution, amount of contact force, and pressure distribution patterns. Sports-related injuries to the menisci are usually due to unexpected rotational force. A varus or valgus force directed to a flexed knee is another common mechanism of injury to the menisci. A valgus force applied to a flexed knee while the femur is internally rotated may cause a tear of the medial meniscus. In contrast, a varus force directed to a flexed knee while the femur externally rotated may result in a lateral meniscus lesion. Because the medial meniscus is more firmly attached than the lateral meniscus, there is a greater incidence of medial meniscus injury. An interesting classification of meniscus injuries was proposed by Arnoczky in 1982. Based on the relation to the meniscal vascular supply, the meniscal injuries can be divided into three main types. When lesions are located within the blood-rich periphery, it is called a red-red tear, and this type of lesion has a better opportunity for healing. When the lesion is encompassing the peripheral rim and central portion, it is called a red-white tear. In this situation, one end of the tear is located in tissue with rich blood supply, while the other end is in the avascular section. A white-white tear is a lesion located in the avascular central portion of the meniscus; the prognosis for healing in such a situation is usually poor.
Frequency of incidence
Meniscal injuries are well known to be fairly common sports-related injuries among adults. However, knee meniscal tears do occur in young individuals who are skeletally immature. They rarely occur in children younger than 10 years with morphologically normal menisci. Generally, meniscal injuries are more common in males than females. This may be due to the aggressive sporting and manual activities that predispose to rotational injuries of the knee and are more common among males. Meniscal injuries have two peaks of incidence during people’s life. They are common in young athletes who are involved in aggressive sports. Moreover, the incidence of meniscal injuries increases in elderly persons older than 55 years because the degenerate menisci are more susceptible to injuries from minor traumas.
How does the patient present?
A thorough and careful history taking is of crucial importance for the clinician to choose the appropriate clinical tests in the physical examination. The clinician will ask about the exact mechanism of trauma and this will help him determine the type of meniscal involvement. On the other hand, the patient will often describe an acute joint pain, and joint effusion may be evident by inspection after a few hours.
However, patients with peripheral tears of the meniscus may develop effusion in just few minutes after trauma. The reason for this is that the outer one third of the meniscus is highly vascularized and the tear is associated with hemarthrosis, which is a bleeding into the joint space.
Locking is another common symptom in meniscal tears and it usually occurs at 20 to 45° of joint extension. Locking is a feeling of a limited joint motion against a rubbery resistance. This happens due to entrapment of a torn fragment within the joint. If joint effusion or capsular involvement is evident, locking-like signs may be positive. The clinician may try to detect a click or snap after the joint unlocks because this is a reliable indicator of meniscal lesion. A patient with meniscal tear may report a sensation of buckling. This sensation develops when the torn fragment becomes lodged momentarily in the knee joint. The buckling sensation should be carefully distinguished from a sensation of giving way, which is commonly associated with anterior cruciate ligament injury due to joint instability. Buckling sensation may also be associated with decreased activity of the quadriceps femoris muscle.
When doctors aim at clinical examination, they rely on the uninvolved leg as a reference for comparison with the findings of the involved leg. Range of motion, girth measurements, gait, and tests for integrity of menisci are all important items to include during clinical examination.
Long-standing meniscal injury often leads to marked atrophy of the vastus medialis oblique segment of the quadriceps femoris muscle because the patient is unable to achieve full extension, and most tension is by the vastus medialis oblique segment at near full extension. There is always localized palpable tenderness at the joint line because of the irritated coronary ligaments which function to connect the outside, inferior edges of the medial and lateral menisci to the joint capsule. However, the location of the tenderness is not an indicator of the type of lesion and the amount of effusion is not a sure sign of the presence or absence of a meniscal lesion.
Deviations or compensatory movements in the gait are possible signs in meniscal involvement and full flexion in squatting may be impossible because of the pain.
Doctors may perform stability tests to exclude additional involvement of soft tissue. Other special tests may be used to assess meniscal involvement; however, a positive result of any test does not necessarily establish the diagnosis. These special tests along with other objective findings can help differentiate a meniscal tear from other soft tissue knee injuries.
Positive result indicates tears of the middle or posterior horn of the meniscus. With the patient supine the examiner palpates the joint line and holds the knee with one hand, while the other hand holds the sole of the foot and acts to provide the required movement. With the hip and knee fully flexed, the examiner applies a valgus stress to the knee and rotates the leg externally while extending the knee. Pain and/or an audible click during preforming this maneuver can indicate a torn medial meniscus. In order to test lesions of the lateral meniscus the examiner repeats this process from full flexion but applies a varus stress to the knee and medial rotation to the tibia. Because a recent meta-analysis has reported sensitivity and specificity of about 70%, the test has been reported to be of limited value in the current clinical practice.
This test is used to differentiate between meniscal and ligamentous injuries. The patient is placed in the prone position with the knee flexed to 90 degrees and the leg is stabilized by the examiner’s knee. The examiner distract the knee while rotating the tibia internally and externally. After that the examiner compresses the knee while internally and externally rotating the tibia again. If rotation and distraction is more painful or shows increased rotation in comparison to the normal side, the lesion is most likely to be ligamentous. If the rotation and compression is more painful or shows decreased rotation in comparison to the normal side, the lesion is most likely to be a meniscal injury.
Bounce home test:
While the patient is supine, his or her heel is cupped in the examiner’s hand. The examiner fully flexes the knee then it is allowed to extend passively. The knee should ‘bounce home’ into full extension. The test is positive if full extension cannot be attained and a rubbery resistance is felt because knee movement may be blocked by a torn meniscus.
The patient is instructed to squat with the knee fully flexed and attempt to ‘duck walk.’ A meniscal lesion is indicated if the motion is blocked and knee extension cannot be attained. However, pain during performing this maneuver may indicate patella-femoral joint involvement as well.
The patient stands with his or her knees fully extended rotates the trunk. This particular movement causes compression of the menisci. If the pain is elicited during internal rotation of the tibia, medial meniscal lesion is indicated. However, pain during external rotation of the tibia indicates a lateral meniscal lesion.
Modified Helfet test:
While the patient is prone position, the examiner flexes the knee at 90° and rotates the tibia internally and externally twice, then repeats the rotations with the knee extended. If pain is increased during rotation in either or both knee positions, meniscal tear or joint capsule irritation is indicated. If the pain increases with a valgus force to a flexed and laterally rotated knee, the medial meniscus, medial collateral ligament ‘MCL’, and the anterior cruciate ligament ‘ACL’ are all suspected to be injured, representing the ‘O’Donoghue’ triad.
The examiner compressed downwards along the medial aspect of the knee while the patient is sitting cross-legged. Pain over the medial line of the knee indicates a posterior horn lesion of the medial meniscus.
First Steinmann sign:
The patient is supine position and the knee and hip flexed at 90°. The examiner rotates the tibia internally and externally. Pain in the lateral aspect of the joint with forced internal rotation suggests a lateral meniscus lesion, while pain in the medial aspect of the joint with forced external rotation suggests a medial meniscus lesion.
Second Steinmann sign:
The knee is flexed and joint line is palpated with the examiner’s thumb. The knee is extended while the joint line is palpated. If the tenderness moves anteriorly or increases while the knee is extended, the anterior horn of the meniscus is probably injured.
An injury to the menisci can be misdiagnosed because of other condition that could have similar symptoms. However, careful clinical examination and accurate imaging studies help exclude other differential diagnoses. The differential diagnosis of torn menisci includes medial and lateral collateral ligaments injuries, loose bodies in the knee, anterior and posterior cruciate ligaments injuries and osteochondral fracture. Doctors will always put these diagnoses into account while addressing cases suspected to have meniscal injuries.
Who is at risk of torn meniscus injuries?
Meniscal injuries are most commonly due to a traumatic event in young ‘especially in athletes’ or degenerative changes in older people. The mode of trauma is usually twisting motions or rotations applied to a flexed knee. A sudden pivot, deep squatting, or heavy lifting may put the knee at risk, such as pivoting in basketball. Generally, sports that require sudden turns and stops may put the athlete higher risk of developing a meniscal injury. Football, basketball, tennis and soccer all are sports that involve vigorous motions and put the athlete’s menisci at risk.
The incidence of meniscus tears in children is increasing because they are participating in organized sports at an earlier age. Furthermore, some occupations can increase the risk of developing meniscus lesions. A Danish study has suggested that an association exists between meniscal injuries and occupations requiring kneeling. The results have shown that occupational kneeling increases the risk of degenerative tears in the medial menisci of both knees.
The meniscus weakens with age and its blood supply is decreased. Tears are more common in old people and can result from a minor trauma or repetitive movements like squatting. People with osteoarthritis are at higher risk of tearing their menisci. This is because the cartilage in the knee becomes weaker, thinner and more prone to tear.
How the diagnosis of a torn meniscus is confirmed?
Recently, magnetic resonance imaging ‘MRI’ of the knee has replaced arthrography as the gold standard choice for the menisci. MRI has sensitivity of 95% and specificity of 81% for medial meniscal tears. Sensitivity and specificity for lateral meniscal tears accounted for 85% and 93% respectively. Although MRI is not usually required before arthroscopic surgery for confirming the diagnosis of a torn meniscus, this modality helps provide accurate information about the status of the ligaments and articular cartilage. Giraffe neck sign is a characteristic finding seen on MRI of the medial meniscus posterior root tear ‘MMPRT.’ One study demonstrated that ‘giraffe neck sign’ was observed in 81.7% of all cases with MMPRT. The study results also suggested the combination of giraffe neck, ghost, cleft and radial tear signs are vital for an accurate diagnostic MRI reading in cases with MMPRT. Plain radiographs can help aid the diagnosis since this imaging modality can reveal the decreased joint space or other bone pathologies, such as osteophytes and osteoarthritis. Standing anteroposterior (AP), lateral, tunnel, and skyline views should be included in radiographic evaluation of the knee.
Diagnostic features include high intrameniscal signal extending to at least one articular surface, and that should be seen in at least two slices. In addition, distortion of the normal meniscal morphology if no prior surgery is suggestive of a meniscal tear.
Although not all effusions require aspiration, acute injury associated with hemarthrosis ‘blood in the joint’ is often evacuated for patient comfort. Furthermore, aspiration of bloody fluid from the joint is suggestive of a cruciate ligament tear or a lesion in the peripheral vascular part of the meniscus. If the bloody aspirate contained fat globules, it would be highly suggestive of fractures. Non-bloody fluid is sent to the laboratory for investigations such as cell count, glucose and protein levels, Gram stain, bacterial culture, and other special tests.
Arthrocentesis ‘aspiration of joint fluids’ has both diagnostic and therapeutic values. The procedure is simply accomplished with minimal patient discomfort. The knee is sterilized and anesthetized with local anesthetic to smooth the use of a large-bore needle. Accepted location for aspiration is the level of the joint line which is one cm medial or lateral to the patellar tendon while the patient is seated. Another accepted location is two cm medial or lateral to the anterior-superior patella while the patient is supine. Choosing the appropriate site of aspiration is a matter of operator preference.
Arthroscopy of the knee is a standard diagnostic and therapeutic tool for the diagnosis of a meniscal tear.
An overview of treatment options
One study has suggested that better treatment results in patients with symptomatic unstable meniscal tears are achieved with arthroscopic partial meniscectomy ‘APM’ than with physical rehabilitation program. The study was on 70 patients and it found that although pain and swelling were reduced with rehabilitation program patients, their injured knees continued to have limited range of motion. Moreover, patients who underwent APM showed greater knee function and reported better treatment satisfaction. For these reasons APM was considered superior to physical therapy in treating symptomatic unstable meniscal tears.
Nevertheless, another study reported that a 12-week exercise therapy program in middle-aged patients who are suffering from degenerative meniscal tears can yield to similar results as APM. During the rehabilitation program, many factors affect the pace and aggressiveness of the therapy. These factor include the extent and location of the lesion, the joint stability, and the amount of cartilage degeneration on weight-bearing surfaces and the duration of injury. Therefore, the protocols then should be adjusted to each patient’s status. If a patient is considering non-operative rehabilitation, an aspiration of the knee joint may be useful in order to decrease effusion. Although not usually advocated, athletes rarely need one injection of a corticosteroid to provide a way to control the irritation within the knee for the performance not be affected.
Treatment options for athletes with a meniscal injury
Several factors are considered while making decisions regarding the management of an athlete with a known meniscal injury. The need for surgical intervention is quite evident in people with symptoms such as a locked knee or debilitating pain with clinical or MRI evidence of a torn meniscus. A treatment decision may be controversial in an athlete who has relatively mild symptoms of a meniscal tear because the severity of the symptoms are variable according to for the types of meniscal tears. Bucket-handle tear, for instance, may cause the knee to lock and be severely painful, whereas small vertical or radial tears may cause intermittent symptoms of giving way and mild pain. An initial period of conservative therapy may be indicated if the symptoms are mild intermittent and locking does not occur. This also depends on the activity level and demands of the athlete. In other words, if an athlete has recurrent mild symptoms without impaired ability to compete, he may be a suitable candidate for non-operative management.
Surgical intervention in a torn meniscus
The first goal is to preserve as much of the meniscal viable tissue as possible. Many factors also should be put into account, such as the location, stability, and chronicity of the tear. Additionally, the athlete’s age, presence of degenerative changes and desired timing of return to competition are important factors to be considered.
Partial meniscectomy is a procedure in which the injured meniscus tissue is trimmed away. This procedure is indicated when the tears are not amenable to repair. If the tears are complex, degenerative or of radial patterns, the patient will probably undergo partial meniscectomy. After partial meniscectomy, patients always regain more than 80% satisfactory function at minimum follow up. Factors such as young age, normal joint alignment, minimal or no arthritis and single tear always help guarantee a good outcome.
Meniscal repair is another option and the best candidate for repair is a tear with special characteristics. Peripheral tear in vascularized region ‘red-red tear’ has a better outcome than a tear in the inner less vascularized region. Vertical and longitudinal tear with length of 1 to 4 cm has a better prognosis rather than radial, horizontal or degenerative tear. Overall, meniscal repair has a success rate of 70 to 95%. Meniscal transplantation is indicated in young patients with near-total meniscectomy, especially in the lateral meniscus.
Meniscal transplantation is contraindicated inflammatory or diffuse arthritis, joint instability, marked obesity and misalignment of the joint. This procedure requires 8 to 12 months for the graft to fully heal and the athlete returns to sports after 6 to 9 months. Ten year follow-up showed that there is persistent improvement in pain and function scores as well as radiographic progression of degenerative changes. Meniscal transplantation is an arthroscopic procedure which can be performed on an outpatient or inpatient basis. Healthy cartilage tissue is taken from a cadaver ‘donor’ and frozen. This tissue is called an allograft. The allograft is tested and properly stored to be matched by size to a candidate for the procedure.
Rehabilitation and recovery time
Rehabilitation program is considered as a conservative treatment and after surgical intervention as well. The rehabilitation program as a conservative therapy is similar in principle to the program that follows surgical intervention. In the management of non-operative meniscal injury, cryotherapy and nonsteroidal anti-inflammatory drugs ‘NSAIDs’ play a vital role since these modalities help control the swelling and provide some pain relief. Initially, maintenance of the range of motion of the knee and some activity modification is useful, and the time frame for return to activity is dependent on the severity of the meniscal injury.
Four to seven days following meniscectomy, the patient begins the initial phase of the rehabilitation program when he or she is usually able to bear as much weight as tolerated on the involved limb. Modalities, such as heat/ice contrasts, transcutaneous electrical nerve stimulation and phonophoresis, are used to decrease pain and control swelling. The emphasis during the initial phase is placed on overcoming any limitations to the range of movement and the following exercises are included in the initial exercise program:
- Hamstring contraction:
the patient lies with his or her knees bent to about 10 degrees. The heels are then pulled into the floor in a way that tighten the muscles on the back of the thigh ‘hamstring muscles’. The patient holds in this position for about 5 seconds then relaxes and the exercise should be repeated ten times.
- Quadriceps contraction:
The patient lies on his or her stomach with a towel rolled under the ankle of the involved limb. The patient should try to forcefully straighten his leg as much as possible against the roll and hold for 5 seconds then relax. The exercise should be repeated ten times.
- Straight leg raises:
the patient lies on his or her back with the uninvolved knee bent while the involved knee is straightened. The patient tries to lift the leg about 6 inches and hold for 5 seconds. After that the patient continues lifting in 6-inch increments and holds for 5 seconds each time. The procedure is then reversed, and the leg is returned to the starting position. This is repeated ten times. An advanced technique could be attempted by applying one pound of weight to the ankle and adding up to a maximum of 5 pounds of weight over 4 weeks period.
- Buttock tucks:
While lying down on the back, the patient tightens the buttock muscles for buttocks to be lift up off the ground. The patient should try to hold tightly for 5 seconds and relax. The exercise is then repeated ten times.
- Straight leg raises ‘standing’:
The patient stands supporting his or herself if necessary. The involved leg should then be lifted slowly forward while the knee is kept extended. The patient should hold in this position for a few seconds and then return to the starting position. The exercise is repeated ten times. An advanced technique can be attempted by adding a weight to the ankle. The patient should start with one pound of weight and the build up to a maximum of 5 pounds over a 4-weeks period.
To begin the intermediate phase of rehabilitation, the patient should have full range of movement. The exercises are continued as indicated by the patients’ symptoms, and the patient may progress to strengthening isokinetic and endurance exercises. In this phase, if the athlete’s quadriceps femoris muscle is strong enough to lift 10 pounds, the running program can be initiated. The first stage of the running program would be jogging in place on a trampoline. The following exercises can be included in the intermediate exercise program:
- Terminal knee extension ‘supine’:
The patient lies on his or her back with a towel roll under the knee joint. The patient straightens the knee, which is supported by the roll, and holds for 5 seconds then returns to starting position. The procedure is repeated ten times. An advanced technique can be attempted by adding weight to the ankle. The patient can start with 1 pound of weight and add up to 5 pounds over a 4-weeks period.
- Partial squat with chair:
In this exercise, the patient holds onto a sturdy chair or counter with his or her feet 6 to 12 inches from the chair or counter. Keeping the back straight, the patient slowly bends the knees without going lower than 90 degrees. The patient holds for a few seconds then relaxes and the technique is repeated ten times.
- Quadriceps stretch ‘standing’:
in the standing position with the involved knee bent, the patient gently pulls heel toward buttocks until he or she feels a stretch in the front of the leg. The exercise is then repeated ten times.
During the advanced phase of rehabilitation, patient continues to progress in strengthening exercises while beginning to return to sports activity. If the patient has the ability to run on the treadmill for 10-15 minutes at a speed of 7-8 minutes per mile, track running may be initiated. In this phase exercises are much more advanced and require muscle strength and endurance. The following exercises are done in the advanced phase of rehabilitation:
- Partial knee bend ‘single leg’:
Patient stands supporting his or herself with the back of a chair while the uninvolved knee is slightly bent with toes touching the ground for necessary balance support. Patient slowly lowers himself depending on the involved knee and straightens up again to the starting position. The exercise is repeated ten times and patient should not overdo the technique.
- Step-ups forward:
In this exercise, patient simply steps forward on a 6-inch platform with his or her involved knee and exercise is repeated ten times. The height of the platform can be increased according to muscles strength.
- Step-ups lateral:
This exercise is similar to step-ups forward; however, the platform is placed on the lateral side of the involved limb. Patient can increase the height of the platform as the muscle strength permits.
- Hamstring stretch ‘supine’:
Patient lies on his or her back with the uninvolved knee bent. The patient tries to bend the hip joint and grasps his thigh while straightening the knee joint. After that, patient holds for a few seconds until stretch is felt behind the knee. This technique is repeated and patient may prolong the stretching position as possible for maximum benefit.
- Hamstring stretch ‘supine at wall’:
Patient lies next to a doorway with one leg extended and heel against the wall. The closer patient is to the wall, the more intense the stretch. With knee bent, patient may move the hips toward the wall. Now patient should begin to straighten the knee until the tightness is felt and hold for 5 seconds.
- Exercise bike:
patient should start pedaling for 10 minutes a day. The duration can be increased by one minute a day until patient is pedaling for 20 minutes a day. Additionally, as you the muscles become stronger, slowly increase the tension on the bike is possible.
As the intensity of exercise program increases, patient may experience temporary pain or swelling over the knee. In this situation, exercises should be lessened or stopped and the involved knee should treated with ‘R.I.C.E.’ techniques which include rest, ice compression and elevation.
Medications as nonsteroidal anti-inflammatory drugs are sometimes prescribed by physician in order to control pain and reduce inflammation. The reduction of inflammation aids preventing complications and decrease comorbidity. These medications include Ibuprofen, Naproxen and Diclofenac. Acetaminophen can be prescribed to patients reported with hypersensitivity to Aspirin or other NSAIDs.
Prognosis and pain-free return to sports depend on the severity of the meniscal injury and accompanied comorbidities. Torn meniscus is a risk factor of developing osteoarthritis on the long term due to the increased load on the articular surface of the knee joint.
Finally, athletes should be advised to use certain techniques in order to prevent the incidence of meniscal injuries. They should maintain strong thigh and hamstring muscles and do stretching exercises before and after their training. Appropriate shoes are also crucial and they should suit the activity being performed.