Anatomy Planes & Axes Explained

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Planes and axis are used to describe all osteokinematic movements that occur in a joint. Be aware, that the anatomic position is always the starting position of every movement described. Let’s discuss the different planes first:

The sagittal plane divides the body into a left and right section
The frontal plane divides the body into a front and back section
The transversal or horizontal plane divides the body into an upper and lower half

When an osteokinematic movement takes place in a certain plane, bones rotate around an axis.

When a movement takes place in the sagittal plane, we are seeing a rotation around or perpendicular to the transversal also called the frontal axis.

When we see a movement in the frontal plane, we are describing a rotation around the sagittal axis. You can remember the sagittal axis from the zodiac sign Sagittarius who is shooting an arrow through your heart.

Lastly, when we see a movement in the transversal plane, we are describing a movement around the longitudinal axis.

During observation of a certain movement in a certain plane, you should take the following position: perpendicular to the respective plane, in the extension of the axis around which the movement takes place.

Before you describe a movement in a joint, you should ask yourself how many degrees of freedom this joint has. As the shoulder joint is a ball-and-socket joint morphologically and functionally, its level of freedom is 3, which means it can move in all three planes.

If we are moving the shoulder in the sagittal plane, it means that we are moving around the transversal axis. These movements in the shoulder joint are called flexion or anteversion or extension or retroversion.

If we are moving the shoulder in the frontal plane, we are moving around the sagittal axis. These movements are called Abduction and ADDuction.

The movements of the shoulder in the transversal plane around the longitudinal axis are called external or lateral rotation and internal or medial rotation.

Hip Joint: the hip joint is a ball-and-socket joint and therefore has 3 degrees of freedom as well. If we are moving the hip in the sagittal plane, we are moving around the transversal axis. These movements are called flexion and extension. If we are moving the hip in the frontal plane, we are moving around the sagittal axis. These movements are called Abduction and Adduction. The movements of the hip in the transversal plane around the longitudinal axis are called external or lateral rotation and internal or medial rotation.

Knee joint: The knee joint is morphologically and functionally a hinge joint, which means that It only has one degree of freedom. It can only move in one plane.

The only real movements that can happen in the knee joint are flexion and extension. As we have learned, these movements only take place in the sagittal plane around the transversal axis. We will neglect the minimal amount of internal and external rotation in the transversal plane, as well as abduction and adduction in the frontal plane.