Original Editor - Rachael Lowe
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Clinically Relevant Anatomy
Anterior and posterior meniscal horns attach to the intercondylar eminence of the tibial plateau. The coronary ligaments provide peripheral attachments between the tibial plateau and the perimeter of both menisci. The medial meniscus is also attached to the medial collateral ligament, which limits its mobility. The lateral meniscus is connected to the femur via the anterior (ligament of Humphrey) and posterior (ligament of Wrisberg) meniscofemoral ligaments, which can tension its posterior horn anteriorly and medially with increasing knee flexion. The transverse ligament provides a connection between the anterior aspects of both menisci. The increased stability provided by the ligamentous attachments prevents the menisci from being extruded out of the joint during compression.
The meniscus is typically an avascular structure with the primary blood supply limited to the periphery. Only the peripheral 10% to 25% of the meniscus is vascularized by vessels are derived from the middle, medial, and lateral geniculate arteries. For that reason, when meniscus is damaged in the central portion it is usually unable to undergo a normal healing process. The most peripheral portion of the meniscus which has a blood supply and is more likely to heal.
Mechanism of Injury / Pathological Process
Meniscal tears are either due to an excessive force applied to a 'normal' meniscus or a normal force acting on a degenerative meniscus. The most common mechanism of injury is a twisting injury on a semi-flexed limb through a weight bearing knee. It may also be associated with other ligamentus injuries, typically the ACL and the MCL. In addition, with age, the meniscus begins to deteriorate often developing degenerative tears and predisposing to traumatic tears. Radial tears are short tears which extend from the medial rim towards the lateral rim of the meniscus. A circumferential tear extends along the length of the meniscus, these types of tear may not go through the full depth of the meniscus, but if they do, they are called bucket-handle- tears, A horizontal split in the body of the meniscus is usually called a horizontal cleavage tear, The flap tear is also horizontal but at the surface of the meniscus rather than in the middle. Sometimes the meniscus may be avulsed rather than torn where there may be symptomatic instability.
Meniscal cysts usually form by influx of synovial fluid through microscopic and gross tears in the substance of the meniscus, however in the absence of a meniscal tear, it has been proposed that a parameniscal cyst may develop from a compression injury to the periphery of a meniscus that has central degeneration.
- joint line tenderness and effusion, either medially or laterally, however it is worth remembering that because the inner portion of the meniscus is avascular and without nerve supply an injury to the meniscus can result in no pain or swelling.
- symptoms are frequently worsened by flexing and loading the knee, activities such as squatting and kneeling are poorly tolerated.
- complaints of 'clicking', 'locking' and 'giving way' are common
- Joint line tenderness has been reported to be the best common test for meniscal injury.
- McMurray's test positive if a pop or a snap at the joint line occurs while flexing and rotating the patient's knee.
- Apley's test performed with the patient prone, and with the examiner hyperflexing the knee and rotating the tibial plateau on the condyles.
- Steinman's test performed on a supine patient by bringing the knee into flexion and rotating.
- Ege's Test is performed with the patient squatting, an audible and palpable click is heard/felt over the area of the meniscus tear. The patient's feet are turned outwards to detect a medial meniscus tear, and turned inwards to detect a lateral meniscus tear.
Tears that are stable and that do not cause significant mechanical symptoms may be treated with simple observation and physiotherapy intervention. Tears that are unstable and contribute to mechanical symptoms are treated with operative intervention such as a Arthroscopic Meniscectomy or a Meniscal Repair.
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Recent Related Research (from Pubmed)
- Cartilage adaptation after anterior cruciate ligament injury and reconstruction: implications for clinical management and research? A systematic review of longitudinal MRI studies.
- Clinical value of routine use of thin-section 3D MRI using 3D FSE sequences with a variable flip angle technique for internal derangements of the knee joint at 3T.
- ↑ Arnoczky SP, Warren RF. Microvasculature of the human meniscus. Am J Sports Med. 1982;10:90-95.
- ↑ Robert S. P. Fan, Richard K. N. Ryu, (2000) Meniscal Lesions: Diagnosis and Treatment. Medscape Orthopaedics &amp;amp;amp;amp;amp;amp;amp;amp;amp; Sports Medicine 4(2)
- ↑ Meserve BB, Cleland JA, Boucher TR. (2008) A meta-analysis examining clinical test utilities for assessing meniscal injury. Clinical Rehabilitation, 22(2), 143-61.