A meniscus root tear involves the complete detachment of the meniscus at its anchor point on the tibial bone, specifically in the posterior horn region. This injury is highly problematic because the meniscus is the knee’s primary shock absorber, and its function depends entirely on this firm attachment. When the root tears, the entire meniscus becomes unstable, biomechanically mimicking the effect of surgically removing the entire structure, a procedure known as total meniscectomy. The goal of a Meniscus Root Repair, typically using a transtibial pullout technique, is to re-establish this attachment to preserve the knee joint and prevent rapid deterioration.
The Critical Role of the Meniscus Root
The primary function of the meniscal root attachment is to convert the vertical weight placed on the knee into a horizontal force called “hoop stress.” This circumferential tension pushes the meniscus outward against the joint capsule, allowing it to bear and distribute up to 50% of the load in the knee. Losing the root attachment causes an immediate failure of this system, leading to profound biomechanical instability.
Once the root is torn, the meniscus shifts or “extrudes” out of the joint space, often defined as a displacement of more than three millimeters. This extrusion dramatically increases the contact pressure on the underlying articular cartilage by reducing the joint’s contact area. The resulting altered load distribution is the main reason an untreated meniscus root tear leads to a rapid progression of osteoarthritis (OA) within a few years. Patients with an unrepaired tear have a high rate of converting to total knee arthroplasty (TKA), providing a strong rationale for surgical intervention.
Defining and Measuring Repair Success
Success in meniscus root repair is measured using both clinical metrics and objective structural evidence, reflecting the dual goal of pain relief and joint preservation. Clinical or functional success is commonly assessed using Patient-Reported Outcome Measures (PROMs), such as the Lysholm score and the International Knee Documentation Committee (IKDC) subjective score. Patients typically show significant functional improvement, with reported Lysholm scores averaging in the mid-80s at two-year follow-up, demonstrating a substantial return to activity and reduced pain.
Structural success focuses on the long-term health of the joint and the integrity of the repair itself. A key metric is survivorship analysis, which tracks the percentage of patients who avoid the need for a total knee replacement over time. Long-term studies show a superior 10-year survival rate for the knee joint following repair, sometimes reaching nearly 80%, compared to rates as low as 44% for patients who underwent a meniscectomy.
Radiographic evaluation is also used to determine structural healing, assessing the reduction of meniscal extrusion and the slowing of joint space narrowing. Advanced imaging techniques can reveal the quality of the meniscal tissue, which may indicate ongoing degenerative change even six months after repair. Healing of the attachment site is a major factor, with reported failure or re-tear rates ranging from approximately 5% to over 20%, depending on the study and patient population.
Patient and Injury Factors Affecting Outcomes
The success of a root repair is influenced by specific patient and injury-related variables that affect the knee’s overall environment. A primary factor is the presence of existing cartilage damage, known as a chondral lesion, with high-grade damage often leading to poorer outcomes. The patient’s body weight, quantified by a high Body Mass Index (BMI), is also a risk factor for repair failure due to increased mechanical loading on the healing tissue.
Knee alignment plays a major role, as uncorrected varus malalignment—a bow-legged knee—places excessive stress on the medial compartment, compromising the repair. When varus alignment is present, an osteotomy to realign the leg may be performed concurrently with the root repair to offload the affected area.
The timing of the surgery is another factor, as acute tears generally have better outcomes than chronic, retracted tears, which are more difficult to reattach anatomically. Failure to address any concomitant injuries, particularly to stabilizing ligaments, can also lead to a poor result. While advanced age was once considered a contraindication, recent studies suggest that age alone should not disqualify a patient, as success has been demonstrated in older cohorts.
Rehabilitation and Long-Term Joint Health
The success of the meniscus root repair hinges on patient adherence to a slow, meticulously staged post-operative rehabilitation protocol. Due to the delicate nature of the bone-to-tendon healing, a strict period of non-weight bearing (NWB) is required, typically lasting four to six weeks. During this maximum protection phase, the knee’s range of motion (ROM) is carefully restricted, often to 90 degrees of flexion or less, to protect the repair site from excessive tension.
Around six to eight weeks, patients gradually progress to protected weight-bearing and begin to increase their ROM, moving into the moderate protection phase. The early stages of physical therapy focus on restoring quadriceps muscle control and a normal walking pattern before advancing to strengthening exercises.
Full return to sports and high-impact activities is typically a long process, often recommended between nine and twelve months post-surgery, reflecting the time required for biological healing. Poor compliance with this slow, staged protocol is a recognized risk factor for repair failure, distinguishing the technical success of the surgery from the ultimate biological healing.