The role of iliocapsularis in hip pathology: a scoping review

Abstract

The iliocapsularis is a relatively unheard-of muscle, located deep in the hip covering the anteromedial capsule of the hip joint. Little is known about this constant muscle despite its clinical relevance. The aims of this scoping review are to collate the various research studies reporting on the detailed anatomy and function of iliocapsularis and to demonstrate how inter-individual differences in iliocapsularis can be used as a clinical adjunct in guiding diagnosis and treatment of certain hip joint pathologies. A computer-assisted literature search was conducted based on Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Our review found 13 studies including 384 cases meeting our inclusion criteria. About 53.8% of the studies involved human cadavers. The current scoping review indicates the relevant anatomy of the iliocapsularis, being a small muscle which arises from the inferior border of the anterior inferior iliac spine and anteromedial capsule of the hip joint, inserting distal to the lesser trochanter. Therefore, based upon these anatomical attachments, iliocapsularis acts as a dynamic stabilizer by tightening the anterior capsule of the hip joint. Implications of this association may be that the muscle is hypertrophied in dysplastic or unstable hips. Determining the size of the iliocapsularis could be of conceivable use in patients with hip symptoms featuring signs of both borderline hip dysplasia and subtle cam-type deformities. Although future research is warranted, this study will aid physicians to understand the clinical importance of the iliocapsularis.

Fig. 1.

The PRISMA flow diagram.

Fig. 2.

An illustration indicating the various anatomical attachments of the iliocapsularis, direct and indirect head of rectus femoris, labrum and capsule of the hip joint to the right hip. Mean measurements of the area of the superior and inferior facets of the AIIS, plus the mean width of the AIIS ridge are indicated with 95% confidence intervals shown in brackets. Illustration retrieved from Phillipon et al. (2014) [14].

Fig. 3.

An image derived from micro-computed tomography indicating the shallow groove of the anteromedial surface of the AIIS (indicated by use of arrowheads) where the iliocapsularis was suggested to arise from. The dashed lines correspond roughly to the superior portion of the AIIS and anterolateral wall of the ilium. The star indicates the smooth impression at the inferior portion of the AIIS. Ant= anterior, Med= Medial, Post = posterior, Sup = superior. Image describes the anteromedial (A), anterior (B) and anterolateral (C) aspects of the right hip. Image retrieved from Tsutsumi et al. (2019) [16].

Fig. 4.

An image demonstrating the borders of the stability arc, outlined in red. The borders are composed of the dynamic muscular stabilisers [iliocapsularis (ic), gluteus minimus (gm) and reflected head of the rectus femoris (rf)] and static stabilizing limbs of the iliofemoral ligament (ILFL-h and ILFL-v) which lie directly beneath the gluteus minimus and iliocapsularis, respectively. The greater trochanter (GT), AIIS, and anterior capsule (C) are labelled for orientation purposes. The red arrows demonstrate the tension which arises during dynamic movements across the anterior capsule as the limbs of the arc contract to stabilize the hip joint. The black dashes indicate the location of a standard interportal medial capsulotomy. Image retrieved from Walters et al. (2014) [15].