Definition
The anatomical position is a fixed posture that anatomists and clinicians agree to picture when describing where structures lie. Its components are precise:
- Body: standing upright.
- Head and eyes: facing forwards, with the gaze directed to the horizon.
- Upper limbs: hanging by the sides, with the palms facing forwards and the thumbs pointing away from the body.
- Lower limbs: close together, with the feet flat on the ground and the toes pointing forwards.
Terminologia Anatomica, the international standard for anatomical names, assumes this position for all its terms of relation.
Why a fixed reference is needed
A fixed reference posture makes anatomical descriptions unambiguous regardless of how the patient is lying or standing. A surgeon operating on a prone patient, a radiologist reading a scan and an anatomist holding a detached bone all use the same words to mean the same thing.
For example, the sternum is always anterior to the heart, even when the patient lies face down and the sternum is nearest the floor. The thumb is always lateral, even when the hand is turned palm down. Without this convention, terms such as anterior, superior, medial and lateral would change meaning every time the body moved.
Consequences for the limbs
Because the palms face forwards, the forearm is supinated in the anatomical position. The radius and ulna lie parallel, the radius on the lateral (thumb) side. This explains several naming habits:
- The thumb is described as lateral and the little finger as medial.
- The radial and ulnar sides of the forearm and hand are used as synonyms for lateral and medial, because they stay fixed when the forearm rotates.
- The front of the hand is the palmar surface and the back is the dorsal surface.
A common error is to picture the arms hanging with the palms facing the thighs. That is the neutral or mid-prone position, not the anatomical position, and it changes which way the thumb points.
In the lower limb, the feet point forwards and the front of the knee faces forwards. The lower limb rotates medially during development, so its extensor surface faces forwards; the upper limb rotates laterally, so the elbow points backwards. The sole is the plantar surface and the top of the foot the dorsal surface.
Other body positions
Clinical positions describe how a patient is actually placed, and they are separate from the anatomical position.
| Position | Description | Typical use |
|---|---|---|
| Supine | Lying on the back, face up | Abdominal examination, most operations |
| Prone | Lying on the front, face down | Spinal surgery, posterior approaches |
| Lateral decubitus | Lying on one side | Lumbar puncture, hip and thoracic surgery |
| Lithotomy | Supine with hips and knees flexed and legs supported | Perineal, gynaecological and urological procedures |
| Trendelenburg | Supine, tilted head down | Pelvic surgery, central venous access |
Whatever the clinical position, anatomical descriptions still refer to the standing anatomical position.
Clinical relevance
Consistent reference to the anatomical position prevents errors in documentation, imaging and surgery. Right and left always mean the patient's right and left, never the observer's. Wrong-side surgery is a recognised never event, which is why the operative site is marked on the patient before surgery and checked again in the theatre safety briefing.
Imaging follows the same convention. A chest radiograph or axial CT slice is displayed as if the viewer faces the patient, so the patient's right side appears on the viewer's left. Clinicians must read the side marker rather than assume.