Chronic knee pain, often stemming from conditions like osteoarthritis, can significantly impact daily life, making simple activities such as walking or climbing stairs difficult. This persistent discomfort arises when the protective cartilage within the knee joint deteriorates, leading to bone-on-bone friction. For many individuals experiencing severe and debilitating knee pain, where non-surgical treatments no longer provide sufficient relief, knee replacement surgery offers a viable solution. This procedure involves resurfacing the damaged areas of the knee with artificial components, aiming to alleviate pain and restore function.
The Meniscus and Its Function
Within a healthy knee joint, two C-shaped pieces of fibrocartilage, known as menisci, reside between the thigh bone (femur) and the shin bone (tibia). Each knee contains a medial meniscus on the inner side and a lateral meniscus on the outer side.
These structures serve several important functions. They act as natural shock absorbers, distributing the load and stress placed on the knee during movement, which helps prevent excessive wear. The menisci also contribute to knee stability by improving the fit between the femur and tibia. Furthermore, they aid in joint lubrication by facilitating synovial fluid distribution.
Meniscus in Total Knee Replacement
During a total knee arthroplasty (TKA), the procedure typically involves removing both the medial and lateral menisci. This removal is necessary to create space for the artificial components and ensure proper implant function. The surgical process involves resurfacing damaged bone and cartilage from the ends of the thigh bone and shin bone. These areas are then replaced with metal and plastic components, including a femoral component for the thigh bone, a tibial component for the shin bone, and a durable plastic insert placed between them.
Meniscus in Partial Knee Replacement
In contrast to a total knee replacement, a partial knee arthroplasty (PKA) offers a different approach when only a specific section of the knee is damaged. This procedure focuses on replacing only the affected compartment of the knee, leaving the healthy parts of the joint intact. The knee is divided into three main compartments: medial (inner), lateral (outer), and patellofemoral (front). If damage, such as osteoarthritis, is confined to just one of these areas, a partial replacement may be considered. In such cases, the healthy meniscus tissue located in the unaffected compartments of the knee is typically preserved, meaning not all meniscal tissue is removed during a partial knee replacement.
What Replaces the Meniscus in Knee Surgery
In a total knee replacement, where the natural menisci are removed, the artificial components are designed to functionally replace their roles. The metal femoral and tibial components, along with the plastic insert, provide a smooth, low-friction surface for movement. The plastic insert, positioned between the metal components, acts as the new bearing surface, mimicking the cushioning and load distribution of the original menisci. For partial knee replacements, the preserved healthy meniscus tissue continues to perform its natural functions in the untouched areas of the knee. In the replaced section, the artificial components handle the mechanics of load bearing and movement, similar to how they function in a total knee replacement.