The zones of the meniscus are determined by what factor?

The correct answer is based on the understanding of how blood supply influences the classification of the meniscus. The meniscus has distinct zones that are defined primarily by their vascularity, which is the availability of blood supply. This is crucial because different regions of the meniscus heal at different rates due to the presence or absence of blood supply. The outer zone, known as the red-red zone, has a rich blood supply and is therefore better able to heal if injured. The middle zone, or red-white zone, has a limited blood supply, making it less capable of healing. The inner zone, or white-white zone, is avascular, meaning it has no blood supply, which severely limits its capacity for self-repair.

Understanding that blood supply is the key factor allows for better management and treatment strategies for meniscal injuries, as interventions may vary depending on the specific zone affected. Other options, such as joint movement, patient age, or meniscal shape, do not directly determine the zones but can influence overall knee health or injury susceptibility.