Chapter 8: The Hip

Structure and Function

Iliofemoral Joint

The hip joint, more specifically called the iliofemoral joint, links the lower extremity with the trunk. The proximal joint surface is the acetabulum, which is formed superiorly by the ilium, posteroinferiorly by the ischium, and anteroinferiorly by the pubis (Fig. 8.1). The concave acetabulum faces laterally, inferiorly, and anteriorly and is deepened by a fibrocartilaginous acetabular labrum.¹ The distal joint surface is the convex head of the femur. The joint is enclosed by a strong, thick capsule, which is reinforced anteriorly by the iliofemoral and pubofemoral ligaments (Fig. 8.2) and posteriorly by the ischiofemoral ligament (Fig. 8.3).

Osteokinematics

The hip is a synovial ball-and-socket joint with 3 degrees of freedom. Motions permitted at the joint are flexion–extension in the sagittal plane around a medial–lateral axis, abduction– adduction in the frontal plane around an anterior–posterior axis, and medial and lateral rotation in the transverse plane around a vertical or longitudinal axis.¹ The axis of motion goes through the center of the femoral head.

Arthrokinematics

In an open kinematic (non-weight-bearing) chain, the convex femoral head rolls in the same direction and slides in the opposite direction to movement of the shaft of the femur. In flexion, the femoral head rolls anteriorly and slides posteriorly and inferiorly on the acetabulum, whereas in extension, the femoral head rolls posteriorly and slides anteriorly and superiorly. In medial rotation, the femoral head rolls anteriorly and slides posteriorly on the acetabulum. During lateral rotation, the femoral head rolls posteriorly and slides anteriorly. In abduction, the femoral head rolls superiorly and slides inferiorly, whereas in adduction, the femoral head rolls inferiorly and slides superiorly. Refer to Chapter 1 for the explanations of slide, spin, and roll (e.g., Figs. 1.2, 1.3, and 1.4, respectively).

Capsular Pattern

The capsular pattern is characterized by a marked restriction of medial rotation accompanied by limitations in flexion and abduction. A slight limitation may be present in extension, but little or no limitation is present in lateral rotation and adduction.²

Range of Motion Testing Procedures: Hip

Landmarks for Testing Procedures