The meniscus is a C-shaped, rubbery piece of fibrocartilage located within the knee joint. It acts as a cushion, distributing weight evenly and absorbing shock between the thigh bone (femur) and the shin bone (tibia). The menisci also contribute to knee stability by deepening the joint surface and improving the fit between the bones. They play a role in joint lubrication and protecting the articular cartilage from wear and tear during movement.
The Meniscus’s Blood Supply
The meniscus has a limited blood supply, which significantly influences its healing ability. Its vascularity is not uniform, leading to distinct zones. The outermost portion, known as the “red zone,” has a rich network of blood vessels. This area receives direct blood flow primarily from branches of the geniculate arteries.
Moving inward from the red zone, there is a transitional area called the “red-white zone.” This middle region has some blood supply, but it is less extensive than the red zone. The innermost portion, known as the “white zone,” is largely avascular, lacking direct blood supply. This absence of blood vessels influences how injuries in this area are managed.
How Blood Supply Influences Healing
The different vascular zones of the meniscus directly correlate with its healing potential. Tears located in the “red zone” have a better chance of healing due to the presence of blood vessels. These vessels deliver oxygen, nutrients, and healing factors to the injured site, facilitating tissue repair.
Conversely, tears in the “white zone” have a poor to non-existent healing capacity. The lack of direct blood supply means that healing cells and essential nutrients cannot effectively reach the injured tissue. While synovial fluid, which bathes the knee joint, provides some nutrition to the avascular regions, it is generally insufficient to support significant tear repair. Tears in the “red-white zone” have an intermediate healing potential.
Treatment Approaches for Meniscus Tears
The location of a meniscus tear, and consequently its vascularity, largely dictates the chosen treatment strategy. For tears located in the vascular “red zone,” meniscus repair is often the preferred approach. This involves surgically suturing the torn edges of the meniscus back together, aiming to preserve the tissue due to its higher healing potential. The goal of repair is to restore the meniscus’s function and prevent future complications.
Tears in the avascular “white zone” are generally not amenable to repair because the tissue lacks the blood supply needed for healing. In these cases, a meniscectomy, which is the surgical removal of the damaged portion of the meniscus, is typically performed. This procedure removes the torn, non-healing fragments that can cause pain, clicking, or locking of the knee.
For tears in the “red-white zone,” the decision-making process is more nuanced. Depending on factors such as the specific tear pattern, its size, patient age, and activity level, a repair attempt might be considered, or a partial meniscectomy could be performed. While non-surgical management, including rest and physical therapy, may be initial considerations for some tears, surgical interventions are often guided by the tear’s location within these distinct vascular zones.