The meniscus is a crescent-shaped piece of fibrocartilage within the knee joint, acting as a buffer between the thigh bone (femur) and the shin bone (tibia). It is susceptible to tears from sudden twisting or degenerative changes that occur over time. Because meniscal injuries are common, many people question whether this small piece of tissue is necessary for the long-term health and function of the knee. Understanding the consequences of its absence helps appreciate the biomechanical role it plays in the body’s largest joint.
Essential Functions of the Meniscus
The primary role of the meniscus is to distribute mechanical load across the knee joint, acting as a shock absorber. By conforming to the shape of the bones, it significantly increases the contact area between the rounded end of the femur and the flat top of the tibia. Without the meniscus, forces transmitted through the knee would be concentrated on a much smaller point, leading to excessive pressure on the underlying cartilage.
The meniscus also contributes to joint stability by improving the fit between the femur and tibia, a concept known as joint congruence. When the knee bears weight, the meniscus converts vertical compressive force into circumferential tension, or “hoop stress,” which helps absorb impact. Furthermore, the meniscal tissue assists in the distribution of synovial fluid. This fluid provides lubrication and delivers nutrients to the articular cartilage covering the ends of the bones.
When Removal is Necessary
Meniscal tissue is often damaged through acute traumatic injury, typically involving a forceful twist or rotation of the knee while the foot is planted. Traumatic tears are common in younger, active individuals and cause symptoms like pain, swelling, or a feeling that the knee is “locking” or catching. In older adults, tears are often degenerative, resulting from the tissue weakening and fraying over years, sometimes without a specific injury event.
When a symptomatic meniscal tear cannot be repaired due to its type or location, a surgical procedure called a meniscectomy is performed. Surgeons prefer a partial meniscectomy, which involves removing only the torn fragment while preserving as much healthy tissue as possible. Complete removal, or a total meniscectomy, is rare but sometimes necessary if the entire structure is irreparable. The goal of meniscectomy is to eliminate pain and mechanical obstruction, restoring the knee’s immediate function.
Long-Term Consequences of Meniscus Absence
The removal of meniscal tissue, even partially, significantly alters knee biomechanics, leading to meniscal deficiency. The primary long-term consequence is the accelerated degeneration of the articular cartilage covering the ends of the femur and tibia. Without the cushioning and load-distributing effects of the meniscus, the stress placed on the articular cartilage increases dramatically.
This concentrated force accelerates wear and tear, leading to the development of osteoarthritis, a progressive disease characterized by the loss of joint cartilage and bone spur formation. Studies indicate that a partial meniscectomy can increase the risk of developing knee osteoarthritis by up to seven times compared to an uninjured joint. The resulting joint instability and chronic pain can lead to decreased activity levels and muscle weakness. Furthermore, the amount of meniscal tissue removed correlates directly with the severity and speed of degenerative changes.
Life After Meniscectomy: Management and Preservation
For individuals who have undergone a meniscectomy, long-term joint health relies on proactive management to slow degenerative changes. Physical therapy is a fundamental strategy, focusing on strengthening the muscles surrounding the knee, particularly the quadriceps and hamstrings. Stronger muscles provide dynamic support and help absorb some of the load the removed meniscus can no longer handle.
Maintaining a healthy body weight is effective for reducing compressive forces transmitted through the knee joint. Even a modest reduction in body mass can significantly lessen the strain on the articular cartilage. To minimize impact, individuals should favor low-impact exercises, such as swimming, cycling, or walking, over high-impact activities like running or jumping sports. These techniques protect the remaining articular cartilage and maximize the functional lifespan of the knee.