Chapter 5, Problem 1RE

Summary Introduction

To list: The planes in which each movement of glenohumeral joint movements occur, and the axis of rotation for each movement in the plane.

Introduction: The shoulder joint is also called a glenohumeral joint. It is structurally classified as a socket joint or synovial joint and functionally classified as a multiaxial joint and diarthrosis. The shoulder joint articulates between the head of the humerus and the glenoid cavity of the scapula.

Explanation of Solution

a. Abduction: Abduction in the shoulder joint is defined as the humerus’ upward lateral movement in the frontal plane. Abduction occurs in the frontal plane about the sagittal axis of rotation.

b. Adduction: Adduction is the downward movement of the humerus in the frontal plane medially toward the body from abduction. Adduction occurs in the frontal plane about the sagittal axis.

c. Flexion: Flexion is the straight anterior movement of the humerus from any point in the sagittal plane. Flexion of the shoulder joint occurs in the sagittal plane of the frontal axis.

d. Extension: Extension is the movement of the humerus straight posteriorly from any point in the sagittal plane. The extension of the shoulder joint occurs in the sagittal plane of the frontal axis.

e. Horizontal adduction: Horizontal adduction is the movement of the humerus in a transverse or horizontal plane toward and across the chest. The plane of motion for horizontal adduction is transverse, and the axis of rotation is vertical.

f. Horizontal abduction: Horizontal abduction is the movement of the humerus in a transverse or horizontal plane away from the chest. The plane of motion for horizontal abduction is transverse, and the axis of rotation is vertical.

g. External rotation: External rotation is the lateral movement of the humerus in the transverse plane around its long axis away from the midline. The plane of motion for external rotation is transverse, and the axis of rotation is vertical.

h. Internal rotation: Internal rotation is the medial movement of the humerus in the transverse plane around its long axis toward the midline. The plane of motion for internal rotation is transverse, and the axis of rotation is vertical.