The meniscus is a crescent-shaped piece of fibrocartilage that acts primarily as a shock absorber and load distributor between the thigh bone and the shin bone. This tissue is important for stability and reduces friction within the joint, helping to protect the articular cartilage covering the ends of the bones. When the meniscus is torn—a common injury—surgery is often performed to alleviate pain and restore function. Treatment involves either repairing the tissue or removing the damaged portion, which raises the question of whether meniscus surgery increases the risk of requiring a total knee replacement (TKR) later in life.
The Established Link Between Meniscus Surgery and Osteoarthritis
The connection between meniscal surgery and the later need for a knee replacement is strongly linked to the progression of knee osteoarthritis (OA). When meniscal tissue is removed or modified, the joint’s biomechanics are fundamentally altered. The loss of the meniscus’s cushioning effect means the load transmitted through the joint is no longer distributed evenly across the joint surfaces.
Removing even a small portion of the meniscus significantly increases contact stress on the articular cartilage. Studies show that removing the central third of the meniscus can increase peak local contact stresses by 65%, and a total meniscectomy can increase this stress by up to 235%. This pressure accelerates wear and tear on the cartilage, leading to post-traumatic osteoarthritis.
Patients who undergo arthroscopic meniscectomy are at a higher risk for premature onset or acceleration of OA. For example, patients with pre-existing OA who underwent partial meniscectomy were up to four times more likely to require a TKR within five years compared to those who received physical therapy alone. The resulting degradation of the cartilage and narrowing of the joint space is the primary reason a total knee replacement becomes necessary.
How Surgical Type Impacts Long-Term Knee Health
The specific surgical approach used to treat the meniscal tear plays a defining role in the long-term health of the knee joint. The two main types are meniscectomy (removing damaged tissue) and meniscal repair (stitching the torn tissue). Modern orthopedic surgery aims to preserve as much meniscal tissue as possible due to its impact on joint longevity.
Meniscectomy, particularly partial meniscectomy, carries a higher risk of future joint degeneration. Removing the torn fragment permanently alters the knee’s load-bearing capacity, contributing directly to the increased risk of osteoarthritis and TKR. The extent of the removal correlates directly with the degree of increased risk, with total meniscectomy posing the highest risk.
Meniscal repair involves suturing the torn edges, allowing the tissue to heal and restore its natural function as a shock absorber. Preserving the meniscus helps maintain normal joint mechanics, significantly lowering the rate of progression to OA and the need for a TKR. Patients who underwent meniscal repair had a significantly lower rate of conversion to total knee arthroplasty (9.8%) compared to those who underwent meniscectomy (36%). Although repair requires a longer rehabilitation period, it is the preferred option when the tear type and location allow for joint preservation.
Factors That Increase the Need for Knee Replacement
Beyond the type of surgery, several patient-specific and injury-specific variables increase the likelihood of needing a total knee replacement.
Patient and Pre-Existing Factors
Patient age is a significant factor; younger patients who undergo meniscectomy have a longer lifespan for OA to develop and progress, leading to TKR at an earlier age. Patients between 40 and 50 years old, particularly women, are at risk for poor long-term outcomes. Individuals who already have mild osteoarthritis face an increased risk of requiring a TKR, as the surgery accelerates the existing process.
Body Composition and Injury Severity
A high Body Mass Index (BMI) or obesity places greater compressive forces on the knee joint. This compounds the effects of a reduced meniscal cushion and accelerates cartilage wear. The complexity and location of the original tear are also predictors of poor outcomes. Tears involving both the medial and lateral menisci, or complex tear patterns, confer a higher risk of progressing to end-stage OA.
Post-Operative Compliance
Failure to fully comply with post-operative physical therapy can compromise the stability and strength around the joint. Stability is necessary to compensate for altered mechanics following meniscectomy or to support a healing repair. Addressing these factors is key to mitigating the long-term risk to the knee joint.