The two pubic bodies are joined in the midline by a non-synovial symphyseal joint [3], which together with the sacroiliac joints helps stabilize the pelvis, especially against the shear forces experienced during walking and running. A fibrous capsule completely encircles the joint and is normally low signal intensity on all MRI pulse sequences. The inferior capsule, referred to as the arcuate ligament, is the thickest portion [3]. The arcuate ligament merges with the aponeuroses of the gracilis and adductor longus [1]. A midline fibrocartilaginous disc sits between the opposing bone surfaces, which are covered by hyaline cartilage. Not uncommonly, however, a fluid-filled vertically oriented cleft will be visible on water-sensitive images centrally within this disc. Just off the midline, along the anterolateral surface of each pubic bone is a variable size tubercle. A secondary ossification along the anteromedial aspect of each pubic bone appears around adolescence, but these do not fuse to the rest of the pubic bones until age 20–25 years [2, 4].

The rectus abdominis muscles are enclosed in a sheath that may be visible as a thin low signal intensity structure on high resolution MRI or CT (Fig. 8.4). Superiorly the muscles have a broad origin on the ribs with the linea alba separating the two medial heads [1, 5]. Distally, separate medial and lateral muscle bellies are sometimes identifiable on cross-sectional images and these taper down to an aponeurosis cephalad to the pubic symphysis. On each side the aponeurosis wraps over the anterior edge of the pubic bone and then turns posteriorly where it is continuous with the proximal tendon of the adductor longus [2, 5, 6]. This common aponeurotic plate (sometimes referred to as the “prepubic aponeurotic complex” or PPAC) is anchored on the anteroinferior edge of the pubic symphysis, and can typically be seen in its entirety on parasagittal images approximately 3 mm from the midline (Fig. 8.2). The fibers of the aponeurosis blend with both the fibrocartilaginous disc and the pubic bone hyaline cartilage anteriorly [2]. The right and left aponeurotic plates also fuse together across the midline just above the adductor origin. On transverse images the normal aponeurosis is a continuous low signal intensity linear structure crossing the midline anterior to the pubis. On coronal images the lateral edge of the aponeurosis curves slightly downward; the appearance has been likened to a “mustache” underneath the pubic symphysis (Fig. 8.1).

Along the inferolateral edges of the aponeuroses originate the two adductor longus tendons, which slightly diverge from each other as they extend caudally into their muscle bellies. The adductor longus tendons lie anterior to the other adductors. They can be recognized by their triangular shape in all imaging planes (Figs. 8.1 and 8.2) [5]. The proximal adductor longus tendon has a direct attachment to the medial pubic bone in addition to its contribution to the prepubic aponeurotic complex [2].

A common, fused tendinous origin of the gracilis and adductor brevis has been described [7]. The main origin of the adductor brevis is muscular, located posterior, lateral, and inferior to the adductor longus on the pubic bones; the adductor brevis frequently will also have some tendon fibers attaching to the symphysis [2]. The pectineus muscle lies along the lateral edge of the rectus abdominis muscle and it attaches to the superior pubic ramus posterior to the rectus abdominis. The pectineus muscle forms the floor of the femoral triangle and is visible deep to the femoral neurovascular bundle on cross-sectional images (Figs. 8.1 and 8.4) [5]. The adductor magnus muscle originates on the inferior ischiopubic ramus and ischial tuberosity, separate from the pubic body [1]. Other than the gracilis, which inserts on the tibia, the adductor muscles insert distally on the femur and work together to stabilize the pelvis during the swing phase of locomotion.

From superficial to deep, the external oblique, internal oblique, and transversalis abdominis muscles support the anterolateral abdominal wall. These muscles form a recognizable layered appearance on cross-sectional images near their attachments on the iliac wings (Fig. 8.4). The thick inferior edge of the external oblique aponeurosis forms the inguinal ligament [5]. Medially, the external oblique aponeurosis is thin, splitting to form the lateral border of the external inguinal ring, and then merging with the superficial rectus sheath. The internal oblique and transversalis fascia comprise the posterior abdominal wall and join with the deep rectus sheath (Fig. 8.4); a defect in the transversalis fascia corresponds to the internal inguinal ring [5]. The inguinal canal lies along the lateral border of the distal rectus abdominis muscle. In men the canal contains the spermatic cord; in women, the round ligament.