It is not possible to tear your natural meniscus after undergoing a total knee replacement (TKA) because the native menisci are removed during the procedure. The knee pain, clicking, or catching sensations that feel similar to a meniscal tear are instead caused by issues related to the prosthetic components or the surrounding soft tissues. While the original anatomy is replaced, mechanical problems can persist, leading to symptoms that mimic a torn meniscus.
The Meniscus and Total Knee Replacement Surgery
The primary goal of total knee replacement is to remove damaged bone and cartilage surfaces, including the menisci, and replace them with artificial implants. During surgery, the surgeon removes the ends of the thigh bone (femur) and shin bone (tibia) to create a flat, prepared surface. The native meniscal tissue must be excised completely so the metal components sit flush against the bone and the implant functions correctly.
The function of the meniscus—acting as a shock absorber and smooth bearing surface—is taken over by a synthetic part. This component is a high-density plastic spacer, made of polyethylene, which sits between the metal components. This polyethylene insert is the new bearing surface, allowing the metal femoral component to glide smoothly on the metal tibial tray, minimizing friction and distributing forces.
Mechanical Pain Mimicking a Tear
The clicking, catching, and sharp pain associated with a meniscal tear can be caused by mechanical issues involving the polyethylene insert or surrounding soft tissues. The plastic spacer is susceptible to wear over time, producing tiny particles that can irritate the joint lining. In a modular design, the polyethylene insert can sometimes slightly shift or subluxate within the metal tibial tray, causing a mechanical sensation when the knee moves.
Soft tissue issues are also a common cause of pain that feels like a tear. Scar tissue, known as arthrofibrosis, can form around the joint and get pinched between the metal components during movement. Patellar tracking problems, where the kneecap (patella) does not glide correctly, can also cause catching and pain. This malalignment may be due to component position or tightness in the surrounding ligaments and muscles. Patellar clunk syndrome is another issue where a fibrous nodule forms on the kneecap tendon and catches as the knee bends.
Structural Failure and Component Loosening
More severe and persistent symptoms that may be mistaken for a tear can result from structural failure within the joint replacement itself. The most common structural complication is aseptic loosening, the breakdown of the bond between the bone and the metal components. This occurs when the cement or the bony interface fails, leading to micromotion of the implant under weight-bearing stress. This instability causes deep, throbbing pain that is often worse with activity and may develop years after the initial surgery.
Particle debris from the worn polyethylene insert can also trigger a biological reaction called osteolysis. In this process, the body’s immune system attempts to absorb the particles, inadvertently destroying the surrounding bone. This bone loss further compromises the implant’s fixation, contributing to loosening and instability. Chronic infection or a periprosthetic fracture (a break in the bone near the implant) can also cause sudden, severe pain and structural instability.