The hip joint, or coxa, 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).
An anterior view of the right hip joint.
An anterior view of the right hip joint showing the iliofemoral and pubofemoral ligaments.
A posterior view of the right hip joint showing the ischiofemoral ligament.
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.
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.
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 no limitation is present in either lateral rotation or adduction.2
RANGE OF MOTION TESTING PROCEDURES: Hip
Landmarks for Testing Procedures HIP FLEXION
Motion occurs in the sagittal plane around a medial-lateral axis. Hip flexion range of motion (ROM) for adults is 120 degrees according to the American Academy of Orthopaedic Surgeons (AAOS)3 and 100 degrees according to the American Medical Association (AMA).4 The mean ROM for males and ...