The shoulder joint is a shallow ball-and-socket joint between the humerus (upper-arm bone) and the glenoid fossa of the scapula (shoulder blade.) The shoulder is a unique joint in that it has only one bony attachment to the rest of the skeleton in the clavicle (collarbone) where it attaches to the scapula. This unique anatomy allows a huge range of motion for the shoulder joint.
Abduction
Abduction is a term that refers to a body part moving laterally away from the body. In the case of the shoulder, this refers to the arm swinging out from the side of the body, in an arm-flapping motion. Range of motion is measured with the palm facing the side of the body and the arm held straight. It is measured from neutral (the arm hanging loosely at the side of the body) to the highest point the arm can be lifted. Normal range is 150 degrees.
Flexion
Flexion is also referred to as forward flexion. In the case of the shoulder, forward flexion is the motion of the shoulder when lifting the arm in front of the body, such as to point at something in front of you. Range of motion is measured with the palm facing the side of the body and the arm straight. It is measured from neutral to the highest point the arm can be lifted over the head. Normal range of motion is 180 degrees.
Extension
Extension is a shoulder motion involving moving the arm behind the body, such as reaching into a back pocket. Range of motion is measured with the palm facing the side of the body and the arm straight. It is measured from neutral to the highest point the arm can be lifted behind the back. Normal range of motion is between 45 and 60 degrees.
Lateral Rotation
Lateral rotation is often referred to as external rotation. It is a motion that is performed with the elbow bent to 90 degrees and swinging the forearm away from the body, such as when opening a cabinet door. The range of motion is measured with the elbow bent to 90 degrees and from neutral (with the elbow against the body and the forearm in front of the body) to the widest point that the forearm can move away from the body. Normal range of motion is 90 degrees.
Medial Rotation
Medial rotation is often referred to as internal rotation. It is a motion that is performed with the elbow bent to 90 degrees and swinging the forearm toward from the body, such as when closing an open cabinet door. The range of motion is measured with the elbow bent to 90 degrees and from neutral (with the elbow against the body and the forearm in front of the body) to the widest point that the forearm can move toward the body. Normal range of motion is 70 to 90 degrees. Internal rotation can also be measured by use of Apley's scratch test.
Apley's Scratch Test
Apley's scratch test is an orthopedic test designed to challenge the shoulder's ability to internally rotate and adduct (bring the arm closer to the body) as well as abduct and externally rotate. The first part of the test involves reaching down past the low back and then up between the shoulder blades, such as when scratching an itch low on the back. This part tests adduction and internal rotation. The second part of the test involves reaching over the head and down between the shoulder blades, such as when scratching an itch high on the back. This part tests abduction and external rotation.
Normal range of motion is considered to be when the shoulders are bilaterally equal and symmetrical.
