zona orbicularis

The circular fibers form a collar around the femoral neck called the zona orbicularis.

The zona orbicularis acts like a buttonhole on the femoral head and assists in maintaining the contact in the joint.

The zona orbicularis, which lies like a collar around the most narrow part of the femoral neck, is covered by the other ligaments which partly radiate into it.

The circular fibers, the zona orbicularis, are most abundant at the lower and back part of the capsule where they form a sling or collar around the femoral neck.

They include the iliofemoral ligament, the teres ligament, the pubofemoral ligament, the ischiofemoral ligament, and the zona orbicularis ligament.

The zona orbicularis or annular ligament is a ligament on the neck of the femur formed by the circular fibers of the articular capsule of the hip joint.

The zona orbicularis and proximal hip joint capsule are poorly understood, but recent studies seem to confirm that the proximal to middle part of the articular capsule, including the zona orbicularis, acts biomechanically as a locking ring wrapped around the femoral neck and thus is a key structure for hip stability in distraction.