Table of Contents |
Flexion and extension are typically movements that take place within the sagittal plane and involve anterior or posterior movements of the neck, trunk, or limbs. Flexion decreases the angle of a joint, bringing the bones involved in the joint closer to one another. Extension increases the angle of a joint.
For the vertebral column, flexion is an anterior (forward) bending of the neck or trunk, while extension involves a posterior-directed motion. For the upper limb, all anterior-going motions are flexion and all posterior-going motions are extension. In the lower limb, bringing the thigh forward and upward is flexion at the hip joint, while any posterior-going motion of the thigh is extension. However, knee flexion is the bending of the knee to bring the foot toward the posterior thigh, and extension is the straightening of the knee. Flexion and extension movements are seen at the hinge, condyloid, saddle, and ball-and-socket joints of the limbs.
Lateral flexion of the vertebral column occurs in the frontal plane and is defined as the bending of the neck or trunk toward the right or left side. Hyperextension is the abnormal or excessive extension of a joint beyond its normal range of motion, thus resulting in injury. Similarly, hyperflexion is excessive flexion at a joint. Hyperextension injuries are common at hinge joints such as the knee or elbow. In cases of “whiplash” in which the head is suddenly moved backward and then forward, a patient may experience both hyperextension and hyperflexion of the cervical region.
Abduction and adduction motions occur within the frontal plane and involve medial-lateral motions of the limbs, fingers, toes, or thumb. Abduction moves the limb laterally away from the midline of the body, while adduction is the opposing movement that brings the limb toward the body or across the midline.
EXAMPLE
Abduction is raising the arm at the shoulder joint, moving it laterally away from the body, while adduction brings the arm down to the side of the body.Similarly, abduction and adduction at the wrist move the hand away from or toward the midline of the body. Spreading the fingers or toes apart is also abduction, while bringing the fingers or toes together is adduction. For the thumb, abduction is the anterior movement that brings the thumb to a 90° perpendicular position, pointing straight out from the palm. Adduction moves the thumb back to the anatomical position, next to the index finger. Abduction and adduction movements are seen at condyloid, saddle, and ball-and-socket joints.
Circumduction is the movement of a body region in a circular manner, in which one end of the body region being moved stays relatively stationary while the other end describes a circle. It involves the sequential combination of flexion, adduction, extension, and abduction at the glenohumeral (shoulder), metacarpophalangeal (finger), or femoroacetabular (hip) joints. Therefore, any joint able to perform circumduction can also perform the other four. This type of motion is found at biaxial condyloid and saddle joints and at multiaxial ball-and-sockets joints.
Rotation is the movement of a bone around a central axis, at a pivot or ball-and-socket joint. Rotation of the neck or body, also known as left and right rotation, is the twisting movement produced by the summation of the small rotational movements available between adjacent vertebrae. At a pivot joint, one bone rotates in relation to another bone. This is a uniaxial joint, and thus, rotation is the only motion allowed at a pivot joint.
EXAMPLE
At the atlantoaxial joint, the first cervical (C1) vertebra (atlas) rotates around the dens, the upward projection from the second cervical (C2) vertebra (axis). This allows the head to rotate from side to side as when shaking the head “no.”Rotation can also occur at the ball-and-socket joints of the shoulder and hip. Here, the humerus and femur rotate around their long axis, which moves the anterior surface of the arm or thigh either toward or away from the midline of the body. Movement that brings the anterior surface of the limb toward the midline of the body is called medial (internal) rotation. Conversely, rotation of the limb so that the anterior surface moves away from the midline is lateral (external) rotation. Be sure to distinguish medial and lateral rotation, which can only occur at the multiaxial shoulder and hip joints, from circumduction, which can occur at either biaxial or multiaxial joints.
Recall that when the body is in the anatomical position while lying face up, it is called the supinated position (s-UP-inated, facing up) and while lying face down, it is called the prone position. These terms also apply to the positioning of the forearm. The proximal radioulnar joint is a pivot joint formed by the head of the radius and the radial notch of the ulna. This joint allows for the radius to rotate along its length. In the anatomical position, the upper limb is held next to the body with the palm facing forward. This is the supinated position of the forearm. In this position, the radius and ulna are parallel to each other. When the palm of the hand faces backward, the forearm is in the pronated position, and the radius and ulna form an X-shape.
Supination and pronation are the movements of the forearm that go between these two positions. Pronation is the motion that moves the palm from the anterior (supinated) to the posterior facing (pronated) position. Supination is the opposite motion, in which rotation of the radius returns the bones to their parallel positions and moves the palm to the anterior facing (supinated) position.
Dorsiflexion and plantar flexion are movements at the ankle joint, which is a hinge joint. Lifting the front of the foot, so that the top of the foot moves toward the anterior leg is dorsiflexion, while lifting the heel of the foot from the ground or pointing the toes downward is plantar flexion. These are the only movements available at the ankle joint.
Inversion and eversion are complex movements that involve the multiple plane joints among the tarsal bones of the posterior foot (intertarsal joints) and thus are not motions that take place at the ankle joint. Inversion is the turning of the foot to angle the bottom of the foot toward the midline, while eversion turns the bottom of the foot away from the midline. The foot has a greater range of inversion than eversion motion. These are important motions that help to stabilize the foot when walking or running on an uneven surface and aid in the quick side-to-side changes in direction used during active sports such as basketball, racquetball, or soccer.
Protraction and retraction are anterior-posterior movements of the scapula or mandible. Protraction is the movement of the scapula or mandible anteriorly (forward). For the scapula, this occurs when pushing against something or throwing a ball. For the mandible, this occurs when the lower jaw is pushed forward, to stick out the chin. Retraction is the opposite—movement of the scapula or mandible posteriorly (backward). For the scapula, this occurs when it is pulled medially toward the vertebral column. For the mandible, this occurs when the lower jaw is pulled backward.
Depression and elevation are downward and upward movements of the scapula or mandible. The upward movement of the scapula and shoulder is elevation, while a downward movement is depression (muscle action). These movements are used to shrug your shoulders. Similarly, elevation of the mandible is the upward movement of the lower jaw used to close the mouth or bite on something, and depression is the downward movement that produces an opening of the mouth.
Excursion is the side-to-side movement of the mandible. Lateral excursion moves the mandible away from the midline, toward either the right or left side. Medial excursion returns the mandible to its resting position at the midline.
Superior and inferior rotation are movements of the scapula and are defined by the direction of movement of the glenoid cavity. These motions involve rotation of the scapula around a point inferior to the scapular spine and are produced by combinations of muscles acting on the scapula. During superior rotation, the lateral end of the scapula (glenoid cavity) moves upward as the medial end of the scapular spine moves downward. This is a very important motion that contributes to upper limb abduction. Without superior rotation of the scapula, the proximal humerus would hit the acromion of the scapula, thus preventing any abduction of the arm above shoulder height. Superior rotation of the scapula is thus required for full abduction of the upper limb. Superior rotation is also used without arm abduction when carrying a heavy load with your hand or on your shoulder. You can feel this rotation when you pick up a load, such as a heavy book bag, and carry it on only one shoulder. To increase its weight-bearing support for the bag, the shoulder lifts as the scapula superiorly rotates. Inferior rotation occurs during limb adduction and involves the downward motion of the glenoid cavity with upward movement of the medial end of the scapular spine.
Opposition is the thumb movement that brings the tip of the thumb in contact with the tip of a finger. This movement is produced at the first carpometacarpal joint, which is a saddle joint formed between the trapezium carpal bone and the first metacarpal bone. Thumb opposition is produced by a combination of flexion and abduction of the thumb at this joint. Returning the thumb to its anatomical position next to the index finger is called reposition.
Below is a table that summarizes the movement you just learned with each joint covered in the last lesson and gives examples of each.
| Type of Joint | Movement | Example |
|---|---|---|
| Pivot | Uniaxial joint; allows rotational movement | Atlantoaxial joint (C1–C2 vertebrae articulation); proximal radioulnar joint |
| Hinge | Uniaxial joint; allows flexion/extension movements | Knee; elbow; ankle; interphalangeal joints of fingers and toes |
| Condyloid | Biaxial joint; allows flexion/extension, abduction/adduction, and circumduction movements | Metacarpophalangeal (knuckle) joints of fingers; radiocarpal joint of wrist; metatarsophalangeal joints for toes |
| Saddle | Biaxial joint; allows flexion/extension, abduction/adduction, and circumduction movements | First carpometacarpal joint of the thumb; sternoclavicular joint |
| Plane | Multiaxial joint; allows inversion and eversion of foot or flexion, extension, and lateral flexion of the vertebral column | Intertarsal joints of foot; superior-inferior articular process articulations between vertebrae |
| Ball-and-socket | Multiaxial joint; allows flexion/extension, abduction/adduction, circumduction, and medial/lateral rotation movements | Shoulder and hip joints |
Source: THIS CONTENT HAS BEEN ADAPTED FROM OPENSTAX "ANATOMY AND PHYSIOLOGY 2E" AT openstax.org/details/books/anatomy-and-physiology-2e
