A total knee arthroplasty (TKA), commonly known as a total knee replacement, is a surgical procedure that involves resurfacing the worn-out joint surfaces of the knee. The goal is to replace the damaged bone and cartilage with metal and plastic implants. The short answer to whether you can tear your meniscus after this procedure is no, because the natural meniscal tissues are removed during the surgery. This article explains why the original meniscus is gone and what mechanical issues may cause similar symptoms to a tear in a replaced knee.
The Fate of the Natural Meniscus During Total Knee Arthroplasty
The menisci are two C-shaped pieces of cartilage situated between the thigh bone (femur) and the shin bone (tibia) in the natural knee. They function as shock absorbers, load distributors, and stabilizers for the joint. During a standard TKA, the primary objective is to create a smooth, clean surface for the artificial joint components to fit precisely.
To achieve this clean surface, the surgeon removes the damaged articular cartilage, bone spurs, and both the medial and lateral menisci. The removal of these tissues is standard practice and is a fundamental part of the procedure. This step prepares the top of the tibia for the flat metal tibial tray component.
Once the joint surface is prepared, the natural tissues that could tear, such as the menisci, are no longer present. The post-surgical anatomy is completely different from the original joint. In rare instances, a remnant of meniscal tissue may be left behind or regenerate, potentially causing pain due to impingement against the implant components.
The Role of the Polyethylene Liner
The function of the removed natural menisci and worn-out articular cartilage is replaced by a specialized component called the polyethylene liner or insert. This component is typically made from highly cross-linked polyethylene, a durable plastic material. The liner is placed between the metal femoral component and the tibial tray, acting as the new bearing surface.
The liner’s purpose is to facilitate smooth, low-friction gliding between the metal components while providing shock absorption and stability. Its presence replicates the cushioning role of the natural tissues, but its material composition is entirely synthetic. Since it is not organic tissue, it cannot experience a meniscal “tear” in the biological sense.
The thickness of this liner is selected by the surgeon to ensure proper ligament balance and stability in the reconstructed knee. While engineered for longevity, the polyethylene liner is still subject to mechanical failure. This failure typically presents as wear, degradation, or fragmentation, rather than a soft-tissue tear.
Sources of Pain Mimicking a Tear
Pain in a replaced knee that feels like a meniscal tear—often involving clicking, catching, or instability—is usually caused by mechanical issues with the implant or surrounding soft tissues. The most common cause of long-term failure requiring revision surgery is aseptic loosening, where the bond between the metal component and the bone fails over time. This loosening often causes pain during weight-bearing activities.
The polyethylene liner, while not tearing, can still fail in ways that produce mechanical symptoms. Over time, the liner can wear down, generating small particles that can trigger an inflammatory response and bone loss (osteolysis). The liner can also fracture, fragment, or dislocate from the metal tray, causing a catching sensation, instability, and acute pain.
Another frequent source of post-TKA discomfort is knee instability, which mimics the feeling of a torn meniscus causing the knee to “give way.” Instability often results from a soft tissue imbalance, improper sizing, or malpositioning of the prosthetic components during the initial surgery. This leads to excessive movement between the femoral and tibial components, often causing clicking or a feeling of subluxation.
Infection, known as periprosthetic joint infection (PJI), is a serious complication causing chronic or persistent pain, sometimes accompanied by warmth, redness, and swelling. While not a mechanical issue, PJI must always be considered in the workup of a painful joint replacement. Soft tissue impingement from scar tissue or nerve irritation can also create localized pain that the patient may interpret as a mechanical problem.
Diagnosis and Management of Post-Surgical Knee Pain
Identifying the exact source of pain in a replaced knee requires a systematic approach, beginning with a physical examination and standard imaging. Initial evaluation involves plain radiographs (X-rays) of the knee, which are excellent for detecting component loosening, malalignment, and bone loss around the implants.
If infection is suspected, blood tests check inflammatory markers like erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP). Joint aspiration, which involves withdrawing fluid from the joint for testing, is often required to confirm or rule out PJI. If initial tests are inconclusive, advanced imaging may be utilized.
Computed Tomography (CT) scans can provide more detail on component rotation and subtle loosening. Magnetic Resonance Imaging (MRI) is generally limited because metal components create artifacts. For minor issues like soft tissue irritation or mild instability, management may involve physical therapy, activity modification, or anti-inflammatory medication. However, mechanical failures such as component loosening, polyethylene liner failure, or severe instability often necessitate revision surgery to replace the faulty implant.