Clinical anatomy of the musculoskeletal system in the hip region.

Although the hip joint is regarded as inherently stable, hip pain and injuries caused by traumatic/non-traumatic hip instability are relatively common in active individuals. A comprehensive understanding of hip anatomy may provide better insight into the relationships between hip stability and clinical problems. In this review, we present our recent findings on the hip morphological characteristics, especially focusing on the intramuscular tendon of the gluteus medius tendon and its insertion sites, hip capsular attachment on the anterosuperior region of the acetabular margin, and composition of the iliofemoral ligament. We further discussed the hip stabilization mechanism based on these findings. The characteristics of the gluteus medius tendon suggest that even a single muscle has multiple functional subunits within the muscle. In addition, the characteristics of the hip capsular attachment suggest that the width of the capsular attachment is wider than previously reported, and its wide area shows adaptive morphology to mechanical stress, such as bony impression and distribution of the fibrocartilage. The composition of the iliofemoral ligament and its relation to periarticular structures suggest that some ligaments should be defined based on the pericapsular structures, such as the joint capsule, tendon, and aponeurosis, and also have the ability to dynamically coordinate joint stability. These anatomical perspectives provide a better understanding of the hip stabilization mechanism, and a biomechanical study or an in vivo imaging study, considering these perspectives, is expected in the future.