The meniscus is a circular, wedge-shaped structure located in the knee. It mainly serves as a shock absorber, and distributes load across the knee joint, The deepened center area also acts as a secondary stabilizer allowing the femur to sit perfectly on the tibia. As well, it aids in the distribution of the synovial fluid (lubrication and nutrition) in the knee joint.
Each knee has a medial and a lateral meniscus, and the differences between the medial meniscus (MM) and lateral meniscus (LM) are as follow:
- MM is more of a C-shape vs LM is more of a circular shape
- MM is less mobile than the LM due to more attachment to the joint capsule and the collateral ligament
- MM is more commonly injured than the LM
- MM is larger in shape compared to the LM
- MM carries a less significant percentage of medial pressure than the LM carries for the lateral pressure
How Does Meniscus Injuries / Tear Happen?
1) Acute meniscus tear – athletes; youngsters
The injury is usually resulting from changing direction, cutting movements, pivoting, and hearing a ‘pop’ sound during movements, or from a direct trauma from colliding with another person. Any axial loading in conjunction with knee rotation or shearing forces can also injure the meniscus.
2) Chronic degenerative tear – elderly
Slow onset, knee pain, locking and often show radiographic evidence of osteoarthritis
How To Diagnose Meniscus Injuries
1) Mechanism of injury – if the mechanism matches what has been stated above
2) Sign and symptoms: joint swelling, pain, locking or catching of the joint,
3) Palpation: joint line tenderness
4) Special tests – positive Thessaly test, positive McMurray test, positive Apley’s compression test
5) Radiographic test – MRI
6) Diagnostic test – Arthroscopy (images for the joint)
How To Treat Meniscal Tear?
Physiotherapy treatment aims at reducing pain, swelling, and inflammation. Increase or maintain pain free range of motion, ensure activities of daily living are not affected. If the injury was not severe, spontaneous healing can happen within 4-6 weeks.
Clinical Pearls:
1) When talking about the meniscus, the term ‘unhappy triad of the knee’ is familiar with the rehab professionals. The person who coined the name found that, when patients suffer from both ACL and MCL tear, there is a 77% chance they have a medial meniscus tear as well.
2) The inner 2/3 of the meniscus has poor blood supply, thus healing is prolonged. In contrast, if the MRI shows that the injury happens in the outer 1/3, consider fast recovery and good prognosis.
3) Studies show that a meniscectomy (removal of meniscus surgically) may increase the contact stress and may accelerate cartilage damage and degeneration due to the lack of shock absorber, thereby increasing the chance of osteoarthritis. Thus, a meniscal repair is preferred over meniscectomy if possible.
4) If possible, conservative treatment such as physiotherapy is preferred over surgical intervention.
Reference: Raj, M. A., & Bubnis, M. A. (2020). Knee meniscal tears. StatPearls [Internet].
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