The knee contains two c-shaped menisci: medial and lateral. Menisci are crucial to knee function and joint health. These structures help to stabilize the knee while optimizing force transmission. A disruption in one or both of the meniscus can cause pain, swelling, and mechanical symptoms (clicking, catching, and popping) in the knee, especially with activity. Options for the surgical treatment of meniscal tears include debridement (partial meniscectomy) and meniscal repair.
The menisci help to distribute loads and stresses on the knee joint. They are made of fibroelastic cartilage. 90% of the collagen they are composed of is Type 1 collagen. The lateral meniscus is useful with posterior movement while the medial meniscus is involved in preventing anterior translation with extension. In an ACL deficient knee, the menisci become imperative stabilizers of the knee joint. To optimize force transmission, the menisci increase contact surface area and absorb shock using their radial and longitudinal fibers. Each meniscus is divided into three distinct zones: white zone, red-white zone, and red zone. The white zone is the furthest inside the knee and has no associated blood flow. The red-white zone is in the middle of the meniscus and has some degree of blood flow. The red zone is the far outer portion of the meniscus and typically has a good vascular supply. This area is supplied by the middle genicular artery and has good healing potential after a meniscal repair. Blood supply is an important consideration in injury healing. Meniscus tears in the central zone have limited natural healing capability.
Everyone is susceptible to a meniscal tear! Meniscal tears are common in athletes as well as in older individuals. Meniscus tears are often associated with a single acute event such as a twist or quick turn that creates a shear force to the meniscus. Additionally, there can be degenerative tearing associated with osteoarthritis of the knee. A medial meniscus tear is more common than a lateral meniscus tear and are the most common indication for knee surgery. ACL tears can be a risk factor to meniscal tears.
Patient will often experience knee pain localized to the affected meniscus(medially or laterally). Pain is exacerbated by activities that involve weight bearing such as squatting, lunging, running, etc. Patients may have difficulty sleeping at night due to the pain or discomfort. Pain is often associated with mechanical symptoms such as popping, clicking, catching, or buckling of the affected knee. A knee effusion can be present with more severe mechanisms of injury.
Diagnosis of a meniscal tear may be suspected by your provided after a through history and physical examination.
Patients often present with tenderness along the joint line (medial or lateral). A positive McMurray’s test, is also a good indicator of meniscal pathology. Other physical exam findings include: positive Apley and Thessaly testing. Global ROM restriction generally suggests advanced osteoarthritis of the knee.
Traditional radiographs are often obtained to rule out a fracture or degenerative process within the knee joint (ex. arthritis). If radiographs are clear of fracture or arthritis, an MRI will likely be ordered to assess the soft tissue structures of the knee. MRI imaging is the image study of choice for diagnosis of a meniscus tear. Though, with knee osteoarthritis, an MRI is often unnecessary for diagnosis as meniscal tears are a common and somewhat expected finding in advanced arthritis of the knee. MRI may reveal a parameniscal cyst associated with the meniscal tear. Classification of meniscus tears are based on their direction, location, size, and pattern of the tear.