Fixation Methods and Treatment Choices for Medial Meniscus Posterior Root Tears (1)

A medial meniscus posterior root tear is a meniscal injury that is easy to miss, yet it can substantially accelerate degenerative change in the knee.

Many patients develop sudden medial knee pain while squatting, going downstairs, or rising from a chair, without a clear collision and without typical locking symptoms.

Treatment requires judging whether the meniscus remains repairable, how advanced the cartilage wear is, whether varus alignment and meniscal extrusion are present, and which fixation method, such as transtibial pull-out fixation or suture anchor fixation, is appropriate.

The meniscus sits between the femur and tibia. It distributes load, absorbs shock, and helps maintain joint stability. The anterior and posterior ends of the medial meniscus are fixed to the tibial plateau through their roots, and the posterior root has a particularly important anchoring role.

Clinically, an avulsion-type injury or radial tear within about 1 cm of the medial meniscus posterior root attachment is usually called a medial meniscus posterior root tear, or MMPRT.

The meniscus can be thought of as a load-bearing ring around the joint surface. When the posterior root is intact, body weight compresses the knee and the meniscus converts part of that vertical load into circumferential hoop tension. Once the posterior root is completely torn, the ring loses its anchor and the meniscus is prone to extrusion beyond the joint margin.

This change can significantly increase contact pressure in the medial compartment. Biomechanical studies indicate that a severe medial meniscus posterior root tear may create mechanical consequences close to those after total meniscectomy. Over time, cartilage and subchondral bone may be exposed to higher loads, and knee osteoarthritis may progress.

This injury is common in middle-aged and older adults, especially in people with degenerative meniscal tissue. Many patients do not recall a major traumatic event; pain may begin suddenly during deep squatting, standing up, walking downstairs, or weightbearing knee flexion.

Varus alignment also deserves attention. Varus knees shift more body weight through the medial compartment, increasing stress on the medial meniscus posterior root. Higher body weight, increasing age, and intrinsic meniscal degeneration may further raise the risk.

Common symptoms include deep medial knee pain, pain with squatting, tenderness along the medial joint line, and sometimes a popping sensation at the moment of injury. Classic meniscal locking or obvious catching may be less prominent in root tears, so the problem can be mistaken for ordinary knee degeneration or a routine meniscal tear.

MRI is currently an important imaging test for evaluating medial meniscus posterior root tears. Clinicians usually review sagittal, coronal, and axial images together.

Typical findings include loss of the expected meniscal signal on sagittal images, often called the ghost sign; a radial defect in the root region on axial images; and interruption of meniscal continuity on coronal images, which also helps assess whether the meniscus has extruded beyond the tibial plateau.

Meniscal extrusion is important for treatment planning. Extrusion of more than about 3 mm beyond the medial edge of the tibial plateau is often used as one reference threshold for marked extrusion, although thresholds vary across methods and studies.

MRI does not detect every posterior root injury. Small partial tears may lack classic signs, so doctors still need to combine symptoms, physical examination, and imaging. Arthroscopy can directly show the exact tear pattern during surgery.

Treatment generally includes nonoperative care, partial meniscectomy, or posterior root repair.

For patients with mild symptoms, inability to tolerate surgery, established severe knee osteoarthritis, or medical conditions that make repair unsuitable, pain control, activity modification, load management, and bracing may be considered.

If there is already marked cartilage degeneration, such as Outerbridge grade 3 to 4 change or later-stage osteoarthritis, simply suturing the root back to its footprint may not reverse established cartilage damage. Some patients may also need high tibial osteotomy, unicompartmental knee arthroplasty, or other treatment depending on varus alignment, cartilage wear distribution, and age.

For patients with relatively preserved cartilage, a repairable root, and early osteoarthritis, preserving and repairing the meniscus is usually more valuable. The aim is to reattach the root near its original tibial footprint, restore hoop tension, and reduce further extrusion as much as possible.

Transtibial pull-out fixation is one of the more established techniques for posterior root repair.

The procedure is usually arthroscopic. The surgeon confirms the tear location, places sutures in the posterior root, then creates a tibial bone tunnel that reaches the original root attachment area. The sutures are pulled through the tunnel to the anterior tibia, tension is adjusted to bring the torn root back near its anatomic position, and fixation is completed on the outer tibial cortex.

One advantage is that the approach is mature and can draw the meniscus directly toward the posterior root footprint. The marrow environment created by the tibial tunnel may also support healing.

Accurate fixation position is critical. If the tunnel exit is too far from the true anatomic root footprint, the meniscus may not regain ideal mechanics even after fixation.

In a 2025 series of 29 patients treated with arthroscopic transtibial traction repair, all patients were followed for at least 24 months. The mean Lysholm score improved from 49.83 before surgery to 83.76 at 2 years, and the IKDC score improved from 50.52 to 84.76. MRI at 2 years found recurrent posterior root tear and meniscal dislocation in 2 patients.

This method requires a tibial bone tunnel, and the sutures extend from the posterior root to a fixation point on the anterior tibia, creating a relatively long fixation construct. Under repeated loading, sutures may elongate or move slightly, a phenomenon often described as the bungee effect.

Sutures may also experience friction as they pass through the bone tunnel. If the patient also needs ACL or other ligament reconstruction, the positions of different bone tunnels must be planned to avoid interference.

Postoperative fixation is only the beginning of healing. Premature weightbearing or deep knee flexion may increase traction on the repaired root, so rehabilitation is usually more cautious than after routine partial meniscectomy.

Suture anchor fixation places an anchor with sutures directly in the original tibial attachment region of the posterior root, then uses the sutures to secure the meniscus back down.

Because long sutures do not need to pass through the entire tibial tunnel, this method may reduce tunnel friction and micromotion from long-distance suspension. From a biomechanical perspective, anchor fixation can provide favorable resistance to displacement and pullout.

The medial meniscus posterior root lies deep within the knee in a narrow space. Traditional anchor techniques may require a posteromedial portal and a relatively high degree of knee flexion, and both visualization and anchor insertion angle can be limited. Operative difficulty may increase in patients with obesity or a narrow medial joint space, and posterior neurovascular structures must be protected.

Newer approaches, including curved guides, soft anchors, and inverted anchor techniques, have been developed to reduce the difficulty of anchor placement and improve fixation.