The most important function of the articular menisci of the knee is to transmit and distribute the load acting on the knee joint especially in association with a more intensive exertion, such as running or jumping. They are also important for maintaining the stability of the knee as well as for lubrication of the joint and nourishment of the cartilage surface.
Typical symptoms of a meniscal injury include pain at the joint line as well as swelling, locking and giving way of the knee.
Today, most meniscal tears are treated conservatively, i.e., by follow-up, symptomatic treatment and rehabilitative exercises.
Choice of an appropriate line of treatment often requires MRI, which makes it possible to define the form of meniscal tear and any associated injuries or findings.
Patients with disturbing symptoms continuing for several weeks, locked knee after acute injury or suspected of having significant associated injuries should be referred to specialized care.
Epidemiology
Meniscal tears are very common, occurring in one in four 50-59-year-old people and nearly all patients over 50 with detectable osteoarthritis of the knee.
Meniscal injuries are more common in men. Medial meniscus tears are the most common..
Most meniscal tears are encountered in people over 35 and no injury is normally necessary for such tears to occur. In such cases, we speak about atraumatic or degenerative meniscal tears. Age-related tissue fragility is a contributing factor.
More rarely, there may be accidental Knee Injuries, or traumatic, meniscal tears. They often occur in people below 30 in association with a sports injury or high-energy injury of the knee. Associated injuries, such as ligament ruptures, are often detected together with a traumatic meniscal tear.
Symptoms and signs
Knee pain appears at the time of (often minor) injury, swelling appears within the first days, and the knee may also lock immediately. Haemarthrosis is not associated with a meniscus tear if the meniscus has not detached from the joint capsule.
Repeated locking and giving way of the knee
Pain in the joint line, the patient feels snapping
Pain on palpation of the joint line at the ruptured meniscus is the most important clinical sign.
Apley's test: The patient lies prone with the knee in 90° flexion. Exerting downward pressure on the sole of the foot pushes the lower leg downwards and compresses the meniscus, which causes pain. Pulling the leg upwards relieves pressure on the meniscus but causes tension on the ligaments and pain. The purpose of the test is to find out whether the pain is due primarily to injury of the meniscus or a ligament.
McMurray's test1: With the patient supine, the knee is first flexed maximally and then extended rotating the leg medially or laterally with varus or valgus stress. The test is repeated palpating the anterior, medial and posterior aspects of the meniscus. If a snap is felt and the patient experiences pain, the test is considered positive.
The diagnosis should be confirmed by MRI.
Types of meniscal tears
Meniscal tears are usually classified according to MRI findings. The most common tear types are vertical longitudinal (bucket handle) tears, oblique (flap) tears, horizontal and radial tears, as well as complex tears which are combinations of these types.
The usual types in young patients are are traumatic tears, i.e., vertical longitudinal tears and, in the lateral meniscus, radial tears. There is often associated injury to the anterior cruciate ligament.
Degenerative tear types, such as horizontal, flap or complex tears are found in older age groups. These are usually located at the medial meniscus.
A more recently identified type of tear, known as a root tear, consists of a tear in the posterior root of the meniscus. Medial root tears are common and not necessarily associated with injury. They are usually found in middle-aged persons with signs of incipient osteoarthritis. Tears of the posterior root of the lateral meniscus often occur in younger age groups, most commonly associated with a traumatic tear of the anterior cruciate ligament.
Treatment
If a meniscal tear is suspected, patients with disturbing symptoms continuing for several weeks, locked knee after acute injury or suspected of having significant associated injuries should be referred to specialized care.
The line of treatment of a meniscal tear depends on the individual symptoms, functional requirements and MRI findings.
Mild symptoms of degenerative tears, in particular, require only follow-up, symptomatic treatment with NSAIDs, and rehabilitative exercises guided by a physiotherapist. Glucocorticoid injections (triamcinolone, methylprednisolone) can be used, as necessary, to treat knee joints with pain at rest and swelling. With these treatments, most meniscal tears become asymptomatic within a few months.
Patients with longitudinal bucket handle tears, root tears of the lateral meniscus or unstable meniscal tears causing prolonged symptoms should be referred to specialized care. A significant share of these can be treated by arthroscopic resection of the meniscus or by fixation.
In cases with significant degenerative changes (Kellgren 3-4) in the knee joint in addition to meniscal tear, resection of the meniscus has not been found to be useful.
After surgical treatment
After meniscal resection, weight-bearing can be allowed as permitted by pain and crutches should be used for a few days. Work disability depends on the patient's work tasks, but sick leave of 2-3 weeks is usually sufficient.
After meniscal fixation, crutches should be used for 2-4 weeks with reduced loading, and rehabilitation should proceed gradually as allowed by scarring of the meniscus. Sick leave is normally needed for 4-8 weeks.
References
Beaufils P, Becker R, Kopf S et al. The knee meniscus: management of traumatic tears and degenerative lesions. EFORT Open Rev 2017;2(5):195-203. [PubMed]
Jarraya M, Roemer FW, Englund M et al. Meniscus morphology: Does tear type matter? A narrative review with focus on relevance for osteoarthritis research. Semin Arthritis Rheum 2017;46(5):552-561. [PubMed]
Ozeki N, Seil R, Krych AJ et al. Surgical treatment of complex meniscus tear and disease: state of the art. J ISAKOS 2021;6(1):35-45. [PubMed]