Flexion and extension
Flexion bends a joint and extension straightens it, and both usually take place in the sagittal plane. At most joints flexion reduces the angle between the two parts; at the elbow and knee, flexion brings the forearm towards the arm and the heel towards the buttock.
- Shoulder and hip: flexion moves the limb forwards, extension backwards.
- Knee: flexion moves the leg backwards because the lower limb rotated medially during development.
- Ankle: dorsiflexion lifts the top of the foot towards the shin; plantarflexion points the toes down. Anatomically, dorsiflexion is extension of the ankle.
- Trunk and neck: flexion bends forwards, extension bends backwards, and lateral flexion bends to one side.
Hyperextension is extension beyond the anatomical position, as at the neck in a whiplash injury.
Abduction, adduction and rotation
Abduction moves a part away from the median plane and adduction moves it back towards it, in the coronal plane. The fingers are an exception: they abduct and adduct relative to the long axis of the middle finger, and the toes relative to the second toe. At the wrist, abduction and adduction are usually called radial and ulnar deviation.
Rotation turns a part around its own long axis in the transverse plane. Medial (internal) rotation turns the anterior surface towards the midline; lateral (external) rotation turns it away. The shoulder and hip rotate in both directions.
Circumduction combines flexion, abduction, extension and adduction in sequence so that the distal end of the limb traces a circle, as at the shoulder or the hip.
Special movements
Several movements have their own names because they occur at particular joints.
| Movement | Description | Where |
|---|---|---|
| Pronation | Turning the palm to face backwards (or downwards with the elbow bent); the radius crosses over the ulna | Proximal and distal radioulnar joints |
| Supination | Turning the palm to face forwards (or upwards) | Radioulnar joints |
| Inversion | Turning the sole to face medially | Subtalar and transverse tarsal joints |
| Eversion | Turning the sole to face laterally | Subtalar and transverse tarsal joints |
| Elevation / depression | Raising / lowering | Scapula, mandible |
| Protraction / retraction | Moving forwards / backwards | Scapula, mandible |
| Opposition | Bringing the pulp of the thumb to meet the pulp of a finger | Carpometacarpal joint of the thumb |
| Reposition | Returning the thumb from opposition | Carpometacarpal joint of the thumb |
Movements of the thumb
The thumb's movements are named in planes rotated about 90 degrees from those of the fingers, because the first metacarpal lies rotated relative to the others. Flexion and extension of the thumb take place in the plane of the palm: flexion carries the thumb across the palm and extension moves it away to the side. Abduction and adduction take place at right angles to the palm: abduction lifts the thumb forwards away from the palm, and adduction brings it back. Opposition combines abduction, flexion and medial rotation at the carpometacarpal joint.
Clinical relevance
Movement terms are the language of examination and documentation. Range of motion is recorded from the anatomical position as zero, so a knee that straightens fully and bends to 130 degrees is written as 0 to 130 degrees. Loss of a named movement points to a specific muscle or nerve: loss of wrist extension (wrist drop) suggests radial nerve injury; loss of thumb abduction suggests median nerve compression; loss of ankle dorsiflexion (foot drop) suggests common fibular (peroneal) nerve injury.
Muscles are described by their roles in a movement: the agonist (prime mover) produces it, the antagonist opposes it, and synergists and fixators steady neighbouring joints so the agonist acts efficiently.