In a knee injury resulting from an external impact, which structure is considered an extra-articular structure?

In the context of knee injuries, extra-articular structures refer to those anatomical components that are located outside the joint space itself. Tendons fit this definition, as they connect muscles to bones and are responsible for facilitating movement, but they do not form part of the joint capsule or the synovial membrane.

Injuries to tendons can occur due to external impacts, leading to conditions such as tendonitis or ruptures, but these injuries do not involve direct damage to the intra-articular structures like ligaments or cartilage, which are contained within the joint capsule.

The synovium and joint capsule are both integral parts of the knee joint itself, serving to enclose and protect the joint space. Juxta-articular bone, which surrounds the joint, interacts directly with the joint structures but is still considered part of the intra-articular environment. Thus, tendons, being located outside these structures, are categorized accurately as extra-articular.