Types of movements in the human body
In order to understand fellow medical students and physicians, you need to have an excellent grasp of the anatomical language. This can simultaneously be a blessing and a curse. If you see the glass half full, the language is extremely precise and exact, leaving no room for errors, misinterpretation, or miscommunication. If you see the glass half empty, there is only one specific term that can accurately describe an anatomical structure/movement/relation, which means there are a lot of words that you need to learn in order to become fluent in this language.
Almost every anatomy department in the world naturally focuses its resources on teaching students the names and details of bones, muscles, vessels, nerves, etc. However, the basic concepts of planes, relations, and especially movements are glanced over in perhaps the first 30 minutes to 1 hour. Planes and relations eventually catch up with students because they are constantly used to relate anatomical structures together, but movements are usually forgotten or poorly understood.
This article will shed some light on the matter by explaining the various types of movements in the human body. They will be grouped in pairs of ‘antagonistic actions’ (actions that oppose one another), just like certain muscle groups.
- Concept of movement
- Lateral/Medial Rotation
- Related Atlas Images
Concept of movement
Without going into complicated physics explanations and equations, movement involves an entity moving from point A to point B. The movement is carried out around a fixed axis or fulcrum and has a direction.
Anatomical movements are no different. They usually involve bones or body parts moving around fixed joints relative to the main anatomical axes (sagittal, coronal, frontal, etc.) or planes parallel to them. Therefore, the template of anatomical movements consists of the following (not all of them are required for every movement):
- Anatomical structures involved in the movement.
- Reference axes around which the movement happens.
- Direction, which in anatomy is usually related to a standard plane, such as the median, medial, sagittal, frontal, etc.
The opposing movements of flexion and extension take place in sagittal directions around transverse axes. Flexion, or bending, involves decreasing the angle between the two entities taking part in the movement (bones or body parts). In contrast, extension, or straightening, involves increasing the respective angle.
Flexion and extension of the knee consists of the following:
- Anatomical structures: The tibia of the leg moves relative to the femur of the thigh.
- Reference axes: The movement is in the sagittal plane. The fulcrum is provided by the knee joint, through which the transverse axis passes.
- Direction: During flexion, the leg moves backwards (posteriorly). During extension, it moves forwards (anteriorly).
Flexion and extension of the elbow joint can be described as follows:
- Anatomical structures: The forearm moves relative to the the arm. More precisely, the ulna (one of the two forearm bones) moves relative to the humerus (bone of the arm).
- Reference axes: The movement is in the sagittal plane. The fulcrum is provided by the elbow joint, through which the transverse axis passes.
- Direction: During flexion, the forearm moves upwards and ‘closer’ to the arm, resulting in a decreased angle between them. During extension it straightens, increasing the angle relative to the arm.
Flexion and extension of the shoulder occurs like this:
- Anatomical structures: The humerus of the arm moves relative to the scapula of the shoulder blade.
- Reference axes: The movement is in the sagittal plane. The fulcrum is provided by the shoulder, or glenohumeral joint, through which the transverse axis passes.
- Direction: During flexion, the arm moves anteriorly and upwards (in full flexion). During extension, it moves posteriorly and downwards. If a full range of motion is performed, it creates an imaginary arc or semicircle.
Flexion and extension of the neck follows the format below:
- Anatomical structures: The skull and cervical vertebrae of the neck move relative to the thoracic vertebrae and upper back.
- Reference axes: The movement is in the sagittal plane. The ‘fulcrum’ is not fixed due to the anatomy and movement of the cervical vertebrae, but it can loosely positioned through the upper thoracic vertebrae. The transverse axis passes through them.
- Direction: During flexion, the head and neck move anteriorly and downwards (in full flexion). Essentially, you are looking down. During extension, it moves posteriorly and slightly downwards.
Flexion and extension of the vertebral column follows the following movement template:
- Anatomical structures: The vertebral column moves relative to the sacrum and hip bone.
- Reference axes: The movement is in the sagittal plane. You can imagine the ‘fulcrum’ as being loosely through the two hip bones and sacrum. The transverse axis passes through them.
- Direction: During flexion, when you are bending forward, the vertebral column moves anteriorly and downwards (in full flexion). During extension, it moves backwards and slightly downwards.
In the world of anatomy, flexion of the foot is referred to as dorsiflexion and plantarflexion. Both movements happen at the ankle joint. Dorsiflexion means flexion of the dorsum (top) part of the foot by reducing the angle between it and the anterior surface of the leg. It happens when you lift the front part of your foot while keeping your heel on the ground.
Plantarflexion is flexion of the plantar (underside) part of the foot by moving it down. This movement happens when you are standing on your toes or pointing them.
The movements of abduction and adduction are intimately related to the median plane. They both generally occur in the frontal plane and are happening around an anteroposterior axis.
Arms & Legs
The easiest examples for understanding abduction and adduction are the legs and arms, which are very similar:
- Anatomical structures: The arm moves relative to the trunk and the shoulder. The leg moves relative to the hip.
- Reference axes: The movement is in the frontal plane. You can imagine the ‘fulcrum’ as axes that pierce the shoulder and the hip respectively, each one following in a forward-backward trajectory.
- Direction: During abduction, you are moving your arm/leg away from the median plane. During adduction, you are moving them towards the median plane. To picture these movements, imagine a child jumping and flailing his/her arms very excitedly in order to grab your attention.
The digits of the hands and feet are also capable of abduction and adduction, but in a slightly specific way. The movements are also related to the medial plane, but this time to the medial plane of the palm or foot, not the body itself.
- Anatomical structures: The digits move relative to the third finger of the hand or the second toe of the foot. These two entities represent the medial planes.
- Reference axes: The movement can be in multiple planes, depending on the orientation of the hand or foot.
- Direction: During abduction, you are moving the digits away from the third finger or second toe, hence spreading them apart from the medial plane. Adduction is the opposite - the digits are brought closer.
The movements of protrusion and retrusion take place in the sagittal plane. They are also related to the transverse axis, but instead of only moving around it, these movements are also taking place parallel to it. Protrusion involves a movement going straight ahead or forward.
Retrusion is the opposite and involves going backwards. Anatomical structures capable of such actions are the tongue, chin (mandible) and lips.
Protrusion and retrusion of the mandible occurs as following:
- Anatomical structures: The mandible moves relative to the viscerocranium (fused bones of the skull forming the face)
- Reference axes: The movement is in the sagittal plane and parallel to the transverse one.
- Direction: During protrusion, the mandible moves directly anteriorly (think underbite). During retrusion, it moves directly posteriorly (think overbite).
These movements are sometimes interchanged with protraction and retraction. However, the latter pair have an additional movement added to them. Protraction is not only an anterior movement, but an anterolateral one as well. This means than the structure moves forwards and laterally. Similarly, retraction also consists of an extra posterolateral movement. The scapulae are the standard example of a bones that perform protraction and retraction.
While protrusion and retrusion move anatomical structures forward and backwards, depression and elevation move them down (inferiorly) and up (superiorly), respectively.
The template for the mandible is as follows:
- Anatomical structures: The mandible moves relative to the viscerocranium (fused bones of the skull forming the face)
- Reference axes: The movement is in the frontal plane. It has a ‘fulcrum’ due to the nature of the temporomandibular joint, which is the transverse plane passing through the two respective joints.
- Direction: During depression, the mandible moves directly downwards. During elevation, it moves directly upwards. You are performing these two movements when you open and close your mouth or during mastication.
Rotation happens in the transverse plane around a superoinferior (longitudinal) axis that happens relative to the median plane. Medial rotation involves bringing the anatomical structure closer to the median plane, while lateral rotation involves moving it further away.
Although very similar, rotations are distinct from abductions/adductions, due to the planes the movements are happening in.
Many anatomical entities take part in rotation, but a few examples are given below.
- Anatomical structures: The head turns relative to the trunk.
- Reference axes: The movement is in the transverse plane. The ‘fulcrum’ is the longitudinal axis passing up and down through the vertebral column and the crown of your head.
- Direction: These two movements happen by changing the position the nose is pointing to. Turning your head laterally corresponds to lateral rotation, while turning it back to look straight ahead corresponds to medial rotation.
- Anatomical structures: The anterior surface of the arm/leg turns relative to the trunk.
- Reference axes: The movement is in the transverse plane. The ‘fulcrum’ is the longitudinal axis passing up and down through the arm/leg itself.
- Direction: These two movements happen by changing the position of their anterior surfaces. By bringing your biceps/vastus muscles towards the midline, you are rotating them medially. If you orientate them in the opposite direction, you are rotating them laterally. For instance, if you are holding a newborn baby, your arms are medially rotated.
Strictly speaking, pronation and supination are considered as two special types of rotation. They are restricted to the forearm and involve the radius twisting over the ulna. The movement template is as follows:
- Anatomical structures: The distal part of the radius rotates around the ulna. Its proximal part rotates in place.
- Reference axes: The movement is in the transverse plane. The ‘fulcrum’ is the longitudinal axis passing through the ulna.
- Direction: Supination is a lateral rotation of the radius, resulting in the palm of the hand facing anteriorly (if in anatomical position) or superiorly (if elbow is flexed). In contrast, pronation is a medial rotation of the radius, with the palm ending in opposite directions compared to supination. You are supinating and pronating when you hold a bowl of soup and when you empty it, respectively.
Circumduction is a special type of movement that is actually a combination of many other ones. The overall movement starts with flexion, followed by abduction, extension and finally adduction. The order must be sequential, but it can start from either flexion or adduction. The result is a circular movement. Due to the multitude of movements, circumduction is restricted to ball-and-socket type joints, such as the shoulder and the hip.
Deviation is a special type of movement that is restricted to the wrist joint. The movement happens in a longitudinal plane through the wrist relative to an axis passing from palmar to dorsal through the wrist. It occurs as follows:
- Anatomical structures: The carpal bones move in relation to the radius.
- Reference axes: The movement is in the longitudinal plane through the wrist. The ‘fulcrum’ is the palmar to dorsal axis passing through the capitate bone of the wrist. The joint allowing the movement is the radiocarpal joint.
- Direction: Radial deviation involves the movement of the wrist towards the “thumb side”. Ulnar deviation consists of the moving the wrist towards the side of the little finger (fifth digit). As the angle between the hand and the forearm are reduced, deviation can be referred to as radial/ulnar flexion.
These two movements are restricted to the digits of the hand. Essentially, they involve pinching, such as when sprinkling salt over food or snapping your fingers. Anatomically speaking, opposition involves touching the pad of any one of your fingers with the thumb of the same hand. Reposition is the reverse, which consists of separating them.
The antagonistic movements of inversion and eversion take place relative to the median place and are specific to the foot. In eversion, the plantar side of the foot is moved away from the median plane so that it is turned laterally. In inversion, the plantar side is moved towards the median plane, resulting in a medial turn.
Hyperflexion and hyperextension are exaggerated movements beyond the normal limit permitted by a joint. It can happen in limbs or the vertebral column and can result in ligament tear, damage, or dislocations.
Hyperextension of the vertebral column, which can happen during sudden acceleration and deceleration, is particularly dangerous. The overextension of the cervical part of the column can result in a whiplash injury and can be a potential threat to the integrity of the spinal cord.