Chapter 34. Overview of the Lower Limb

Big Picture

The bones of the skeleton provide a framework that serves as an attachment for soft tissues (e.g., muscles). The bony structure of the gluteal region and thigh, from proximal to distal, consists of the pelvis, femur, patella, tibia, and fibula (Figure 34-1A). Synovial joints and fibrous ligaments serve to connect bones together.

Pelvis

The pelvis is an irregularly shaped bone consisting of right and left pelvic bones. The pelvic bones articulate posteriorly with the sacrum, via the sacroiliac joints, and anteriorly with each other at the pubic symphysis (Figure 34-1A and B). Each pelvic bone has three components: ilium, ischium, and pubis. The acetabulum is a large cup-shaped structure at the junction where the ilium, ischium, and pubis fuse. The acetabulum protrudes laterally for articulation with the head of the femur bone. The three bony components of the pelvis form an opening, called the obturator foramen.

Ilium

The ilium is the most superior and the largest bone of the three components of the pelvis.

• Iliac crest. The entire superior margin of the ilium is thick and forms a prominent crest, which is palpable. The iliac crest is the site for muscle attachment and fascia of the abdomen, back, and lower limb. The iliac crest terminates anteriorly at the anterior superior iliac spine and posteriorly at the posterior superior iliac spine, both providing a site for muscle attachments.
• Anterior inferior iliac spine. A rounded protuberance located just inferior to the anterior superior iliac spine on the anterior surface of the ilium. The anterior inferior iliac spine serves as a site for the attachment of muscles and ligaments.
• Posterior inferior iliac spine. A less prominent spine along the posterior border of the sacral surface of the ilium.
• Iliac fossa. Has an anteromedial surface of the wing, which is concave and forms a large fossa. The iliac fossa serves as a site for muscle attachment.

Ischium

The ischium is the posterior and inferior component of the pelvic bone.

• Ischial tuberosity. The most prominent feature of the ischium, a large tuberosity on the posteroinferior aspect of the bone. The ischial tuberosity is an important site for the attachment of muscles of the lower limb, primarily the hamstrings, and for supporting the body in a seated position.
• Ischial ramus. Projects anteriorly to join with the inferior ramus of the pubis.
• Ischial spine. A prominent spine that separates the lesser sciatic notch from the greater sciatic notch.

Pubis

The pubis is the anterior ...