A lateral meniscal root tear is a tear where the outer meniscus attaches to the bone at the back of the knee. It commonly occurs with an ACL tear and can be easy to miss on an MRI scan. [3]
Root tears matter because they make the knee less stable and increase the load on the cartilage. Repairing the root at the time of ACL reconstruction aims to restore the meniscus’s function and protect the new graft. [1] [2]
At a Glance
- The meniscal roots anchor the meniscus to the bone at the front and back of the knee.
- A torn root means the meniscus can no longer cushion and support the knee properly.
- Lateral root tears are associated with ACL tears and can be difficult to see on MRI.
- A root repair is usually performed at the same time as the ACL reconstruction.
- A missed root tear may lead to faster cartilage wear and a higher risk of ACL graft failure.
What is the meniscal root?
The menisci are C-shaped structures inside the knee that act as shock absorbers and spread your body weight evenly across the joint.
Each meniscus is attached to the bone at the front and back of the joint by its “root” attachments. These roots act as anchor points.
Why is the meniscal root important?
A normal meniscus cups and supports the thighbone (femur). Because the roots are the anchor points, they are vital to this cushioning effect. If a root is torn, this support is lost, which puts more pressure on the cartilage surfaces and may speed up cartilage wear, or arthritis. [1]
The menisci also contribute to knee stability. A lateral meniscal root tear can make the instability of an ACL tear worse. [2] For this reason, Dr Vishal Pai aims to repair the root during an ACL reconstruction to restore more stability to the knee.
How is a lateral meniscal root tear diagnosed?
Lateral meniscal root tears are associated with ACL tears. [3] An MRI scan is used to confirm the ACL tear, but root tears can be difficult to see on MRI, even for an experienced musculoskeletal radiologist.
Surgeons therefore look carefully for a root tear during the arthroscopy (keyhole) part of an ACL reconstruction. The torn root can look intact at first, because it often heals to the joint lining in an abnormal position. When it is tested with a probe, it becomes clear that it has detached from the bone, and a root repair can be performed.
How is a lateral meniscal root tear repaired?
A root repair is usually performed at the same time as the ACL reconstruction. A common technique is to pass high-strength sutures through the torn root and then through a small tunnel drilled in the shin bone (tibia). The tunnel runs from the original root attachment to the front of the tibia, so the root can “dock” back into place. [4]
The sutures are usually tied over a small metal button or secured into the bone with a suture anchor. You can read more about meniscal repair.
What happens if a root tear is missed?
A missed lateral meniscal root tear has two main implications after an ACL reconstruction:
- faster wear of the cartilage in the outer compartment of the knee, because the meniscus is no longer working properly
- a higher risk of ACL graft failure, because the lateral meniscus has lost its role as a secondary stabiliser of the knee. [2]
Summary
Lateral meniscal root tears occur with ACL injuries and can be missed on MRI. Repairing them aims to restore the function of the meniscus, reduce the risk of faster cartilage wear and provide extra stability for the ACL reconstruction.
If you would like to discuss how this applies to your knee, you can book a consultation with Dr Vishal Pai.
References
Show all 4 referencesHide references
- Schillhammer CK et al. 2012. Repair of lateral meniscus posterior horn detachment lesions: a biomechanical evaluation. The American Journal of Sports Medicine.
- Shybut TB et al. 2015. Effect of lateral meniscal root tear on the stability of the anterior cruciate ligament-deficient knee. The American Journal of Sports Medicine.
- Brody JM et al. 2006. Lateral meniscus root tear and meniscus extrusion with anterior cruciate ligament tear. Radiology.
- LaPrade RF et al. 2015. Recent advances in posterior meniscal root repair techniques. Journal of the American Academy of Orthopaedic Surgeons.
Have an ACL injury with a meniscal tear?
Dr Vishal Pai performs ACL reconstruction and meniscal root repair. You can arrange a consultation to discuss your scans, injury and treatment options.
Written by Dr Vishal Pai
Vishal is an experienced knee surgeon based in Bayside, Melbourne. He consults at Sandringham Orthopaedic Specialists and operates at The Avenue Hospital and Calvary Holmesglen Private Hospital. His practice focuses on sports knee surgery, including ACL reconstruction and meniscal repair, as well as robotic knee replacement.