Before discussion of shoulder injuries and diseases, a basic knowledge of the shoulder anatomy is needed. In conveying this knowledge, a certain jargon is often used. This article will attempt to avoid such jargon as much as possible. Nevertheless, healthcare professionals often forget that the lay person may not understand this language. As a function of simple translation, the list below contains many of the common terms used to describe anatomy.

Anatomic position defines the standard orientation of the body. All directions are defined from the body positioned as such:

• Standing straight up, feet together, and flat on the floor, arms positioned against the side of the body with the palms of the hands facing forward. The "front" of the arm contains the bicep muscle.

Directions - how to get around the body

• Anterior = to the front of the body, e.g. the chest, away from the back, the belly-button away from the buttocks
• Posterior = to the back of the body, opposite of anterior
• Superior = to the top of the body, away from the feet
• Inferior = to the bottom of the body, opposite superior
• Medially = toward a line drawn from the nose to the belly-button, this is called the midline
• Laterally = away from the midline toward the outside of the arms

Useful terms in talking about the body:

• Articulate = to come in contact with, e.g. two bones in the same joint
• Fossa = a slight depression in the surface of a structure

A bit about muscle groups

Remember that groups of muscles share functions. An injury to a single muscle or its tendon may show some weakness, decreased mobility and localized pain, but overall range of motion and strength of the shoulder complex may be preserved.

• Muscles of ADduction - these are muscles that ADD the arms to the body. From the anatomic position this would mean squeezing the arms against the side of the body.
• Muscles of ABduction - these are muscles that work as the opposite of the ADDuctors. They raise the arms overhead by keeping the arms straight and lifting them in an arc(like a snow angel).
• Muscles of Internal rotation - the hands out to the side of the body so that the shape is like the letter "T". These muscles move the outstretched hands together in front of the body, lik a seal clapping.
• Muscles of External Rotation - The opposite of internal rotation.
• Muscles of Elevation - this is shrugging the shoulders upward.
• Muscles of Depression - this means lowering the shoulders, the opposite of elevation.
• Muscles of Flexion - from the anatomic position, these muscles move the arms toward the front, as if lifting up a box in front, swinging the arms like a pendulum straight ahead.
• Muscles of Extension - from the anatomic position, the muscles move the arms backward, like a swimmer waiting for the gun.
• The rotator cuff - the muscles of the rotator cuff are the SITS muscles: supraspinatus, infraspinatus, subscapularis and teres minor.