The Shoulder Joint

The shoulder joint, also known as the glenohumeral joint, falls within the joint category of ball-and-socket. Another common ball-and-socket joint is the hip. The shoulder is considered a ball-and-socket joint because the glenoid fossa of the scapula (the joint of the shoulder) connects with the humerus, which is the upper arm bone that has a ball at the upper end. A healthy shoulder without injury normally has eight different directions of ROM. They are flexion, extension, hyperextension, internal rotation, external rotation, circumduction, adduction and abduction.

Flexion, Extension, Hyperextension

Flexion of the shoulder occurs when the arm is brought to a bent position, while extension allows the arm to return to a straight position. Hyperextension is the ability of the arm to go past normal levels of extension, as when moving the arm to the rear of the body with a straightened elbow.

Internal and External Rotation

Internal rotation of the shoulder is the inward turning of the arm, while external rotation is the outward turning of the arm. These rotations can be demonstrated by extending the arm outward to the side of the body, with the elbow facing downward and turning the arm until the elbow faces upward and then back again.

Circumduction

Circumduction of the shoulder involves moving the arm in a full circular movement. This movement is considered to be a blending of all the possible ROM directions in a ball-and-socket joint.

Adduction and Abduction

Adduction of the shoulder is when the arm is moved close to the body, as in placing the arm firm against the side of the body. Abduction is the exact opposite, and is demonstrated when the arm is moved away from the body, as in raising the arm above the head or extending it outward from the body in any direction.