Structure
The fibrous layer of the articular capsule of the hip joint has two groups of fibers, the internal circular fibers, known as the zona orbicularis, and the external longitudinal fibers. The zona orbicularis forms a ring around the head of the femur, and partly coalesce with the pubofemoral and ischiofemoral ligaments. It is the narrowest aspect within the articular capsule (Standring, 2016).
Related parts of the anatomy
Anatomical Relations
The fibers of the zona orbicularis run perpendicular to the hip joint like a sling that encircles the femoral neck, immediately distal to the femoral head. Anteriorly, the fibers coalesce with the deep aspect of the iliofemoral ligament. Superiorly, they are affixed to the femur at the base of the greater trochanter. The fibers also coalesce with the distal aspect of the superior band of the ischiofemoral ligament, then traverse the posterior aspect of the femoral neck, forming the posterior capsule prior to coalescing with fibers of the anteroinferior capsule (McCarthy, Noble and Villar, 2016).
Function
The joint capsule of the hip joint ensures that the joint is sealed, thus, keeping the lubricating synovial fluid within the joint. It provides passive stability to the joint by limiting the joint movement. Additionally, it provides active stability by containing numerous proprioceptive nerve endings which relay mechanical information back to the central nervous system (Ralphs and Benjamin, 1994)
List of Clinical Correlates
—Rheumatoid arthritis
—Osteoarthritis
—Capsule laxity and microinstability
References
McCarthy, J. C., Noble, P. C. and Villar, R. N. (2016) Hip Joint Restoration: Worldwide Advances in Arthroscopy, Arthroplasty, Osteotomy and Joint Preservation Surgery. Springer New York.
Ralphs, J. R. and Benjamin, M. (1994) 'The joint capsule: structure, composition, ageing and disease', Journal of Anatomy, 184(Pt 3), pp. 503-509.
Standring, S. (2016) Gray's Anatomy: The Anatomical Basis of Clinical Practice. Gray's Anatomy Series 41st edn.: Elsevier Limited.
