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PART IV THE LOWER EXTREMITY


11.3 Define femoral torsion in terms of anteversion and retroversion. 11.4 Define the function of the acetabular structures, and explain how their alignment affects hip joint stability and mobility.


11.5 Discuss the open and closed chain osteokinematics and arthrokinematics of the hip joint in femur-on- pelvis and pelvis-on-femur movement.


11.6 Identify the muscles of the hip joint, and describe their function as primary and secondary movers. 11.7 Explain how changes in hip position can alter the function of specific hip muscles.


Note to Students: It is recommended that you review the pretest questions before reading the chapter to better understand the critical elements of the text. As you complete each section, stop and answer the corresponding questions to test your comprehension. The pretest does not cover all the material in each chapter and should not be used as a sole means of self-assessment of knowledge.


HIP COMPLEX STRUCTURES


The hip joint is composed of the head of the femur and the acetabulum of the pelvis. It is a ball-and-socket joint of stability because an extensive joint capsule, labrum, and ligaments reinforce its deep socket. The hip provides an axis for the trunk and pelvis to move on the lower extremity as a person leans forward in a sitting position. It provides the range of motion and strength to move the body upward in standing up from a sitting position. The hip joint plays a major role in functional activities, such as walking, negotiating stairs, running, and lifting and carrying loads. Hip muscular weakness, dysfunction, or both can adversely affect a person’s balance and overall safety. Hip pathology or trauma can result in pain and major disability of the entire body.


BONY STRUCTURES


The bony structures that constitute the hip joint are the bones that make up the pelvis and the femur. The pelvis has two large fl at bones called the innominate bones that are made up of the ilium, the ischium, and the pubis. Each innominate bone begins as three separate bones at birth (Fig. 11.1). These bones are typically fused into one innominate or coxal bone by age 25 and connect the lower extremities to the axial skeleton through the articu- lation between the ilium and the sacrum at the sacroiliac joint. The right and left innominate bones have this pos- terior connection at the sacrum and articulate with each other anteriorly at the pubic symphysis.


The pelvis forms an osteoligamentous ring and serves as an attachment site for many of the large muscles of the trunk and lower extremities. It functions to trans- mit weight from the upper body and trunk to the lower extremities and, along with muscles and connective tissue, provides support for the bowel, bladder, and reproductive


Ilium


The ilium forms the upper anterior portion of the innominate bone and has a bony ridge called the iliac crest. Typically, these crests are level from side to side and can be palpated by placing your hand on the sides of your pelvis similar to the example in Figure 11.3. The most prominent anterior bony projection of the ilium is the anterior superior iliac spine (ASIS), which is also easily palpated. The ASIS landmark is often used in assessing pelvic alignment and measuring leg lengths. Below the ASIS is the anterior inferior iliac spine (AIIS). Posteriorly, the iliac crest ends at a posterior projection called the posterior superior iliac spine (PSIS). The PSIS is often located on the surface of the body by two pos- terior dimples on either side of the sacrum. Interior to the PSIS is the posterior inferior iliac spine (PIIS) above the sciatic notch. The notch and the sacrotuberous and sacrospinous ligaments form the sciatic foramen. On the


Pubis Acetabulum Ischium


Obturator foramen


Figure 11.1 The innominate bone, composed of the ilium, ischium, and pubis. (From Starkey C, Brown D. Examination of Orthopedic & Athletic Injuries, 4th ed. Philadelphia, PA: F. A. Davis Company, 2015, p. 422, with permission.)


organs. The pelvic basin is rounder and wider in females, to accommodate the needs associated with childbearing. Figure 11.2 illustrates the bony structures of the pelvis.


Ilium


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