Types of Body Movements
Every time you bend your elbow, rotate your shoulder, or point your toes, you're performing a specific, named type of body movement. These movements are defined by the plane they occur in and the direction bones move relative to each other. Knowing the terminology is critical for describing joint function accurately in anatomy.
Types of Body Movements
Angular and rotational movements
Angular movements change the angle between two bones at a joint.
- Flexion decreases the angle between two bones by bending a joint. Think of bending your elbow to bring your hand toward your shoulder.
- Extension increases the angle between two bones by straightening a joint. Straightening that bent elbow back out is extension. If you extend past the normal anatomical position (like bending your head backward), that's hyperextension.
- Abduction moves a limb away from the midline of the body. Raising your arm out to the side is abduction.
- Adduction moves a limb toward the midline. Lowering that raised arm back to your side is adduction.
- Circumduction is a combination of flexion, extension, abduction, and adduction performed in sequence, creating a cone-shaped movement. Moving your arm in a full circle at the shoulder is circumduction.
Rotational movements turn a body part around its longitudinal axis.
- Internal (medial) rotation rotates the anterior surface of a limb toward the midline. Turning your arm so your palm faces backward is internal rotation at the shoulder.
- External (lateral) rotation rotates the anterior surface of a limb away from the midline. Turning your arm so your palm faces forward from a neutral position is external rotation.
Special movements
Some movements have specific names because they occur at particular joints and don't fit neatly into the angular/rotational categories.
- Supination rotates the forearm so the palm faces anteriorly (or superiorly if the elbow is flexed). A helpful memory trick: you can hold a bowl of soup in a supinated hand.
- Pronation rotates the forearm so the palm faces posteriorly (or inferiorly if the elbow is flexed). This is the opposite of supination.
- Dorsiflexion pulls the top of the foot toward the shin, decreasing the angle at the ankle.
- Plantarflexion points the toes downward, increasing the angle at the ankle (like standing on your tiptoes).
- Inversion turns the sole of the foot medially (inward).
- Eversion turns the sole of the foot laterally (outward).
- Protraction moves a body part anteriorly (forward), such as jutting the jaw forward.
- Retraction moves a body part posteriorly (backward), such as pulling the jaw back.
- Elevation raises a body part superiorly, like shrugging your shoulders upward.
- Depression lowers a body part inferiorly, like dropping your shoulders back down.
- Opposition is the movement of the thumb across the palm to touch the fingertips. This movement is unique to the saddle joint of the thumb and is what gives humans fine motor dexterity.
Joint structures that determine movement
The type of synovial joint at a given location determines which movements are possible there. Each joint shape permits a specific set of motions.
- Hinge joints allow flexion and extension in a single plane. Examples: elbow, knee, interphalangeal joints of the fingers and toes.
- Ball-and-socket joints are the most mobile, allowing flexion, extension, abduction, adduction, circumduction, and rotation. Examples: shoulder (glenohumeral) and hip (coxal) joints.
- Pivot joints allow rotation around a single axis. The atlantoaxial joint (between C1 and C2 vertebrae) lets you shake your head "no." The proximal radioulnar joint allows pronation and supination of the forearm.
- Condyloid (ellipsoidal) joints allow flexion, extension, abduction, adduction, and circumduction, but not rotation. Examples: metacarpophalangeal joints (the knuckles) and the wrist joint.
- Saddle joints allow the same movements as condyloid joints. The best example is the carpometacarpal joint of the thumb, which also permits opposition.
- Gliding (plane) joints allow limited sliding or twisting movements between flat bone surfaces. Examples: intercarpal joints, intertarsal joints, and the acromioclavicular joint.
Comparing movements at different joints
Joints with the same classification can still differ significantly in their range of motion based on the depth of the socket, surrounding ligaments, and muscle arrangement.
- Shoulder vs. hip joint
- Both are ball-and-socket joints capable of multiaxial movement.
- The shoulder's socket (glenoid cavity) is shallow, giving it the greatest range of motion of any joint in the body, but also making it the most commonly dislocated.
- The hip's socket (acetabulum) is much deeper and reinforced by strong ligaments, making it far more stable but less mobile.
- Elbow vs. knee joint
- Both are hinge joints that primarily allow flexion and extension.
- The knee also permits slight medial and lateral rotation when the knee is flexed. This is why twisting injuries to the knee are common.
- The elbow itself is a hinge, but the proximal radioulnar joint at the elbow region allows pronation and supination of the forearm.
- Wrist vs. ankle joint
- The wrist is a condyloid joint allowing flexion, extension, abduction (radial deviation), adduction (ulnar deviation), and circumduction.
- The ankle (talocrural joint) functions primarily as a hinge, allowing dorsiflexion and plantarflexion. Inversion and eversion occur mainly at the subtalar joint below it.
Key joint components that support movement
- Articulations are the points where two or more bones meet, forming a joint.
- Ligaments connect bone to bone, providing joint stability and preventing excessive movement.
- Tendons connect muscle to bone, transmitting the force of muscle contraction to produce movement.
- Range of motion (ROM) describes the full extent of movement possible at a joint. ROM varies by joint type, individual flexibility, and whether injury or disease is present.