The iliocapsularis muscle (ICM), a small and often overlooked muscle of the anterior hip, has recently gained attention for its potential clinical and surgical relevance. Despite being anatomically distinct and commonly present, the ICM remains underappreciated among clinicians and anatomists. This narrative review aims to synthesize recent anatomical and clinical literature on the ICM, focusing on its origin, insertion, innervation, vascular supply, anatomical variations, histological features, and functional significance. The ICM originates from the anteromedial hip capsule and the anterior inferior iliac spine, typically inserting distal to the lesser trochanter. Its proposed function includes tightening the anterior hip capsule and stabilizing the femoral head. Electromyographic studies suggest that the ICM plays an active role during hip flexion and dynamic gait phases. Anatomical variations, including variant origins and insertions, have been documented, along with unique innervation and fascial compartmentalization. Clinically, the ICM serves as a useful landmark in total hip arthroplasty and periacetabular osteotomies. Its hypertrophy or atrophy has been linked to hip pathologies such as acetabular dysplasia and femoroacetabular impingement. Imaging modalities, including ultrasound and elastography, have further supported its diagnostic utility. This review emphasizes the need for greater recognition of the ICM’s structure and function, underscoring its relevance in orthopedic procedures and hip pathology diagnostics.

Methods: The FT and FA of dried C1 and C2 vertebrae (identified bones; n=107, males=53 and females=54) were observed and measured using a Digital Vernier Caliper (Mitutoyo, Kawasaki, Japan). Anteroposterior (AP) and transverse diameters of the left and right FTs (n=214) were measured and compared between sexes. Variations and types of FT and FA found on the upper vertebrae were recorded and classified. Results: The FT shape of the Thai C1 was AP elliptical, while of that of C2 was transverse elliptical. Compared to females, both diameters of the upper spine were significantly greater in males except for the AP diameter of C2 on the right side. All diameters were significantly different in both sexes and sides except for the AP diameter of C1 and C2. A common type of FT classified in C1 was type 2 (male [69.81%], female [79.63%]) whereas for C2 it was type 1 (male [63.21%], female [59.26%]). Moreover, an incomplete osseous bridge was a major FA subtype observed in the Thai spine. Conclusions FT morphometry has an elliptical shape and diameters are greater in males. The FT and FA variations identified in this study will be useful for surgeons treating vertebral neurovascular injuries of the posterior upper cervical spine in the Thai population.