The meniscus is a c-shaped piece of fibrocartilage that functions as a shock absorber and stabilizer between the thigh bone and the shin bone in the knee joint. When this cartilage is torn, treatment typically involves either a meniscectomy (removing the damaged portion) or a meniscal repair (suturing the torn edges back together). A common question after a repair is whether the injury can happen again. The answer is yes; a repaired meniscus can tear a second time. Understanding the factors that influence the initial repair’s success and subsequent risk management strategies is important.
Understanding the Success Rate of Meniscus Repair
The long-term risk of a repaired meniscus failing or re-tearing is a recognized possibility. Pooled data suggests the re-tear or failure rate ranges from approximately 19% to 26% five years after the initial procedure. This rate is not uniform, as the success of a repair is highly dependent on the biological environment of the tear.
The ability of the meniscus to heal relies heavily on its blood supply, which is divided into zones. Tears located in the “red zone” (the outer one-third) have a rich blood supply and a significantly better prognosis for successful healing following repair. Conversely, tears in the inner “white zone” are avascular, meaning they lack blood vessels. This results in poor healing potential, making surgical repair less likely to succeed.
The pattern of the tear also influences the outcome. Vertical or longitudinal tears are more favorable for repair than complex or radial tears, which are often unstable and disrupt structural integrity. While age was once considered a major limiting factor, modern research suggests a patient’s age is less influential than the tear’s location, type, and blood supply. Tears repaired in conjunction with an anterior cruciate ligament (ACL) reconstruction often show higher healing rates due to the additional blood and growth factors released during the associated bone drilling.
Reducing the Risk of Re-Injury
Successfully healing a repaired meniscus requires rigorous adherence to the post-operative physical therapy (PT) protocol to protect the fragile suture line. For the initial weeks, the knee is often placed in a brace and subjected to non-weight-bearing or partial weight-bearing restrictions. These restrictions prevent excessive compressive and shear forces on the healing tissue. Ignoring these limits can directly compromise the repair and lead to failure before the tissue has fully integrated.
Long-term protection of the knee depends on establishing strong, stable musculature that can absorb shock and control joint movement. Rehabilitation focuses on strengthening the quadriceps, hamstrings, and hip abductors, which are crucial stabilizers for the knee. Exercises progress from non-weight-bearing activities to closed-chain movements like mini-squats and step-ups. Deep knee flexion movements, such as deep squatting, are typically restricted for four to six months to avoid placing high stress on the posterior meniscus.
A gradual return to high-demand activities and sports is important for mitigating the risk of a re-tear. Patients should avoid high-impact, twisting, and pivoting motions for several months, as these rotational forces often cause the initial injury. The knee must demonstrate near-full strength and stability through functional testing before a full return to sport is permitted. This process can take four to nine months depending on the tear’s complexity. Patients must also learn to recognize warning signs, such as persistent localized joint line pain, swelling that does not resolve, or a new clicking or catching sensation, which can indicate a healing problem.
Navigating a Second Meniscus Tear
If a repaired meniscus fails, the symptoms are often similar to the original injury, including a sudden return of sharp pain, instability, and mechanical symptoms like locking or catching. Recurrent locking is especially concerning because it suggests a fragment of the torn cartilage is blocking the knee’s normal motion. Persistent or recurrent pain after a period of improvement should be immediately evaluated, as it may signal that the initial repair has failed to heal completely or that a new tear has occurred.
Diagnosis of a second tear is typically confirmed through a clinical examination and magnetic resonance imaging (MRI). However, a standard MRI can struggle to differentiate a newly failed repair from residual scar tissue, which can appear similar on the scan. In complex cases, a specialized procedure called an MR arthrogram may be used. This involves injecting a contrast dye into the knee joint before the scan to highlight any unhealed gaps or new tears more precisely.
Subsequent treatment options for a failed repair depend on the amount of remaining meniscal tissue. If the re-tear is small or located in a poor healing zone, the surgeon may opt for a partial meniscectomy, trimming away the failed portion to relieve symptoms. For younger, highly active patients with significant meniscal tissue loss, options aimed at preserving the joint surface are considered. These include Meniscus Allograft Transplantation (MAT) using donor tissue, or the implantation of a synthetic or collagen scaffold to promote tissue ingrowth. A second tear increases the long-term risk of developing knee osteoarthritis due to the permanent loss of the meniscus’s joint-protecting function.