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The meniscus is a semilunar shock absorber in the knee, between the upperleg bone (femur) and lowerleg bone (tibia). There are two menisci in the knee: the inner (medial) and outer (lateral) meniscus. Additional functions of the meniscus are spread of synovial fluid as well as a conforming structure to accomodate the rounded femur and flatter tibia. The lateral meniscus is more mobile than the medial meniscus to allow full range of knee motion. The menisci are attached to the joint capsule. The capsule is the soft tissue envelope around the knee. Blood vessels penetrate the meniscus from the capsule. The outer part of the meniscus may heal if ruptured due to its high vascular content. Meniscal ruptures in the less vascularized part have a low tendency to heal. Abnormal movement of the ruptured meniscus is painful due to traction on the joint capsule.
Symptoms of a ruptured meniscus
A meniscus may rupture in case of torsional forces on the knee (eg. football or field hockey knee distortion or ski trauma). The meniscul may also be damaged in deep squatting or due to long periods of overuse (eg. running). Symptoms associated with meniscal rupture are: pain on the inner or outer side of the knee; swelling of the knee joint; pain on squatting or deep bending as well as locking sensation. If the ruptured meniscus is locked in the knee, one can not extend the knee fully.
Types of meniscal lesions
The meniscus rupture may be of various types: a radial tear, flap tear, degeneration and a bucket handle lesion. The rupture may occur in the well or less vascularized part of the meniscus. The better the vascularity, the higher the chance of healing.
First of all, an adequate diagnosis is important. Meniscal lesions often occur together with ligament and cartilage damage to the knee. The rapid, adequate diagnosis and treatment of these lesions is essential for good recovery. The diagnosis "meniscal rupture" is based on the patients history of the knee trauma, complaints and physical examination of the knee. The meniscus can not be seen on an X-ray. However, this X-ray is important to exclude other causes for knee pain. Sometimes, diagnosis of meniscal rupture is made by MRI or by knee arthroscopy.
The meniscus may heal by itself, if ruptured in young patients and if the rupture occurs in well vascularized parts of the meniscus. Squatting and kneeling activities should be prevented in such a case. The knee will react by pain if flexion of the knee is overdone. This may take months to heal. If complaints persist or locking of the knee occurs, an arthroscopy is indicated. Depending on the type of meniscal lesion, I then choose between one of the following treatment modalities:
A small, stable rupture in well vascularized meniscus, may heal by itself. Sometimes, the scar tissue in the lesion is removed to enhance healing. It is important to limit deep squats and kneeling for 3 months after the surgery to allow meniscal healing.
A complex tear or rupture in less vascularized meniscus is best treated by removal of the ruptured tissue (this is called meniscectomy). The meniscal rupture may futher damage the knee joint if left in place.
An unstable tear located at the outer part of the meniscus, may be repaired or trephined (to improve vascular supply to the meniscus). This requires special surgical skills by the orthopaedic surgeon. This can be done in the same arthroscopy most of the time. Sometimes, an additional incision is necessary for adequate meniscus repair. It is done in daycare. After meniscal repair, one must walk on crutches for 6 weeks. No kneeling and deep squatting activiites are allowed for 3 months after the surgery. You may flex the knee without putting weight on the knee. As such, most activities in daily living are feasible. The succes rate of meniscal repair varies between 60-80%.
If possible, meniscal healing is preferable to meniscectomy. Removal of the mensicus increases the risk of knee osteoarthritis in 10-15 years. However, meniscal repair has some disadvantages: rehabilitation is much longer compared to meniscectomy (6 weeks crutches, 3 months no deep squats and kneeling) and some complications may occur = damage to nerves and bloodvessels. Occurrence of complications are rare (< 1 %). For these reasons, I only suture meniscal ruptures that have a good chance of healing.
It is essential to treat additional lesions of the knee in a timely and adequate fashion. This sometimes takes a staged approach. An example is a lesion of the medial collateral ligament. This ligament is often injured together with the medial meniscus in sports trauma. The medial collateral ligament heals without surgery if recognized early (< 2 weeks after trauma) and treated adequately by bracing (day and night for 6 weeks). After recovery of range of motion, arthroscopy may be done for the meniscal lesion. A rupture of the anterior cruciate ligament needs to be addressed if a meniscal repair is done. Reconstruction of the anterior cruciate ligament often occurs in a second operation.
Patient experiences after meniscus injury are documented in Cases.