Anatomy of the hip capsule and pericapsular structures: A cadaveric study

The anatomical literature contains relatively little qualitative or quantitative information regarding the anatomy of the hip joint capsule and its relationship to the surrounding pericapsular structures. We aimed to provide a detailed description of the anatomy of these relationships in a cadaveric study. Dissections of 11 nonpaired, fresh-frozen cadaveric hips were performed, documenting capsular dimensions and attachments to pericapsular structures including the rectus femoris, gluteus minimus, iliocapsularis, and piriformis and short external rotator muscles. Tendon footprints of these pericapsular muscles were measured, as well as their distance from reproducible bony landmarks. The thickest portion of the hip capsule is posterosuperiorly and superiorly near its acetabular origin, while the thinnest portion is posteriorly and posteroinferiorly near its femoral insertion. The piriformis has no capsular contribution; however, the reflected head of the rectus femoris, gluteus minimus, iliocapsularis, and external rotator tendons all demonstrate consistent capsular adhesions. There are complex associations among these structures, yet the surrounding layers of the capsule are confluent in predictable relationships. Knowledge of the intricate relationship between the hip capsule and pericapsular structures presented here will be useful for surgeons as they perform the precise and specific capsular releases required by various operative procedures. This study also provides information that can lead to further biomechanical, radiographic, and clinical studies on these structures.