What is the Meniscus?
Inside each knee, there are two menisci — the medial (inner) and lateral (outer) meniscus.
They are crescent-shaped pieces of cartilage that act like shock absorbers between your thigh bone (femur) and shin bone (tibia).
The menisci have several vital roles:
- Distribute weight evenly across the knee joint
- Absorb shock from walking and running
- Help stabilize the knee
- Protect the joint cartilage from wear
Each meniscus is anchored firmly to the tibia by strong attachments known as meniscal roots.
These roots hold the meniscus in place and allow it to handle and distribute force effectively when you move.
What is a Medial Meniscus Posterior Horn Root Tear?
The posterior horn refers to the back part of the meniscus.
A root tear happens when the meniscus pulls away or tears off from its bony attachment at the back of the knee.
When that root tears, the meniscus can no longer anchor properly. It starts to lose its shape and function, often slipping outward (a problem called meniscal extrusion).
This means the meniscus is no longer effectively cushioning or stabilizing your knee.
In simple terms:
A meniscus root tear is like cutting the anchor of a ship — the structure is still there, but it drifts out of place and stops working as intended.
Intact posterior horn root of a medial meniscus of a right knee.
Surgical view of a posterior horn root tear of the medial meniscus of a right knee.
Why Is a Root Tear a Serious Diagnosis?
A root tear is not just another “meniscus tear.” It disrupts the entire biomechanics of your knee joint.
1. Loss of shock absorption
When the root tears, the meniscus cannot carry the load anymore.
Studies have shown that this is biomechanically similar to removing the entire meniscus — resulting in higher contact pressure on the cartilage (1).
2. Meniscus extrusion
The torn meniscus slides outward, further reducing its ability to protect the knee joint (2).
3. Cartilage wear and osteoarthritis
As the meniscus stops cushioning the joint, the articular cartilage gets overloaded. Over time, this accelerates cartilage breakdown, causing pain, swelling, stiffness, and ultimately knee osteoarthritis (OA) (3,4).
Large studies have shown that meniscus root tears can lead to “accelerated osteoarthritis”, meaning the joint can deteriorate much faster than usual (5,6).
Root Tear → Meniscus Extrusion → Cartilage Overload → Cartilage Damage → Osteoarthritis
Can the Root Be Repaired?
Yes — in many cases, surgical repair of the torn root is possible and beneficial, especially if the knee has not yet developed advanced arthritis.
Common Repair Methods:
- Transtibial pull-out repair: sutures are passed through the meniscus and tied through a small bone tunnel in the tibia.
- Suture anchor repair: sutures are fixed directly to the bone at the root attachment site.
These techniques help reattach the meniscus to its normal position, allowing it to function again and reduce further joint damage (7,8).
Evidence for Repair:
- Meniscus root repair can slow down or prevent progression of knee arthritis (9).
- Patients who undergo repair have lower rates of needing total knee replacement compared to those treated with meniscectomy or non-surgical care (10).
- Repair also improves pain and knee function (11).
Limitations:
- Not all root tears are repairable — outcomes are poorer if there is already severe cartilage loss or leg deformity (bow-leggedness).
- Some residual meniscus extrusion may remain even after repair (12).
- Success depends on factors such as age, weight, knee alignment, and timing of surgery (13).
Key Takeaways
- A meniscus root tear is a serious injury that can trigger early knee osteoarthritis.
- Early diagnosis and repair (if suitable) can help restore knee mechanics and protect your cartilage.
- Leaving a root tear untreated often leads to faster joint wear and pain progression.
- Even after successful repair, maintaining strong thigh muscles, healthy weight, and good alignment is important for long-term knee health.
References
- Bhatia S, LaPrade CM, Ellman MB, LaPrade RF. Meniscal root tears: significance, diagnosis, and treatment. Am J Sports Med. 2014;42(12):3016–3030.
- Koga H, et al. Meniscal extrusion: risk factors and diagnostic tools to predict early osteoarthritis. Orthopedic Reviews. 2022;14(3):74881.
- LaPrade CM, et al. Biomechanical consequences of a complete radial tear adjacent to the medial meniscus posterior root attachment site. Am J Sports Med. 2014;42(3):577–582.
- Choi CJ, et al. Medial meniscus posterior root tear and the development of accelerated knee osteoarthritis. Arthroscopy. 2010;26(10):1379–1384.
- Wang Y, et al. Meniscal root tears and accelerated knee osteoarthritis progression: findings from the Osteoarthritis Initiative. Osteoarthritis Cartilage. 2022;30(5):709–716.
- Chung KS, et al. Meniscus root tears: current concepts and evidence-based treatment. J Exp Orthop. 2021;8(1):30.
- Kim JH, et al. Transtibial pullout repair of posterior medial meniscus root tear: clinical and radiologic outcomes. Knee Surg Sports Traumatol Arthrosc. 2011;19(6):1029–1034.
- Ahn JH, et al. Suture anchor repair for posterior root tear of the medial meniscus: clinical and radiologic results. Arthroscopy. 2015;31(10):1941–1950.
- Chung KS, et al. Outcomes of meniscal root repair versus meniscectomy in middle-aged patients. Arthroscopy. 2020;36(8):2411–2421.
- Bernard CD, et al. Long-term outcomes after medial meniscus posterior root repair: a meta-analysis. Arthroscopy. 2023;39(2):405–418.
- Feucht MJ, et al. Clinical and radiological outcomes after transtibial pullout repair of posterior medial meniscus root tears. Am J Sports Med. 2015;43(8):1951–1956.
- Kim SB, et al. Medial meniscus extrusion after successful posterior root repair. Knee Surg Sports Traumatol Arthrosc. 2018;26(8):2341–2347.
- Ozkoc G, et al. Factors affecting outcome after medial meniscus posterior root repair. Clin Orthop Relat Res. 2021;479(9):1890–1898.
