Abduction and Adduction

Abduction and adduction are paired anatomical movements describing movement of a body part relative to the median plane of the body or, in the digits, relative to a defined reference axis. Abduction generally moves a structure away from the reference plane or axis, while adduction moves it toward that reference.

These movements are especially important at the shoulder and hip joints, where the upper and lower limbs can move laterally in the frontal plane. Similar terminology is used for the fingers and toes, although their reference axes differ from the body's median plane.

Abduction and adduction are fundamental concepts in functional anatomy because they describe joint motion, muscle actions, clinical examination, gait, posture, and many everyday movements.

Definition of Abduction

Abduction is movement away from the median plane of the body. At the shoulder, raising the upper limb laterally away from the trunk is abduction. At the hip, moving the lower limb laterally away from the opposite limb is abduction.

Definition of Adduction

Adduction is movement toward the median plane. Returning an abducted upper limb toward the side of the trunk or bringing an abducted lower limb back toward the opposite limb are examples of adduction.

Abduction Versus Adduction

Movement	General Definition	Example
Abduction	Movement away from the median plane or designated reference axis	Raising the arm laterally
Adduction	Movement toward the median plane or designated reference axis	Lowering the laterally raised arm toward the trunk

Anatomical Position as the Reference

Anatomical movements are described relative to the standard anatomical position. In this position, the body is upright, the upper limbs are at the sides with palms facing anteriorly, and the feet are directed forward.

Using a standard reference position allows the same movement terminology to be applied consistently regardless of the person's starting posture.

Median Plane

The median plane, or midsagittal plane, is the vertical plane passing longitudinally through the center of the body and dividing it into equal right and left halves.

For the limbs, abduction generally means movement away from this plane and adduction means movement toward it.

Plane of Movement

Abduction and adduction usually occur predominantly in the frontal plane, also called the coronal plane. This plane divides the body into anterior and posterior portions.

Axis of Movement

Movement in the frontal plane generally occurs around an anteroposterior axis. This axis extends approximately from the front of the body toward the back.

Plane and Axis

Feature	Abduction and Adduction
Primary plane	Frontal or coronal plane
Primary axis	Anteroposterior axis
General reference	Median plane of body

Shoulder Abduction

Shoulder abduction moves the upper limb laterally away from the trunk. Full elevation of the upper limb requires coordinated movement of the glenohumeral joint and scapula.

The principal muscles responsible for glenohumeral abduction are the supraspinatus and deltoid.

Supraspinatus

The supraspinatus originates from the supraspinous fossa of the scapula and inserts on the greater tubercle of the humerus. It assists initiation of shoulder abduction and contributes to stabilization of the humeral head within the glenoid cavity.

Deltoid

The deltoid is the major muscular contributor to continued abduction of the humerus. Its middle fibers are particularly well positioned to produce abduction after the movement has been initiated.

Scapular Rotation During Abduction

Elevation of the upper limb above shoulder level requires upward rotation of the scapula. This repositions the glenoid cavity and allows continued elevation of the humerus.

The trapezius and serratus anterior are major contributors to upward scapular rotation.

Scapulohumeral Rhythm

Scapulohumeral rhythm describes the coordinated relationship between movement at the glenohumeral joint and movement of the scapula during arm elevation.

This coordination distributes movement across multiple articulations and helps maintain favorable mechanical relationships at the shoulder.

Muscles Involved in Shoulder Abduction

Muscle	Major Contribution
Supraspinatus	Initiates and assists glenohumeral abduction
Deltoid	Major abductor of humerus
Trapezius	Contributes to upward rotation of scapula
Serratus anterior	Contributes strongly to upward rotation of scapula

Shoulder Adduction

Shoulder adduction brings the upper limb toward the trunk from an abducted position. Several powerful muscles can contribute, including the pectoralis major, latissimus dorsi, and teres major.

Pectoralis Major

The pectoralis major acts strongly on the humerus and contributes to adduction and medial rotation of the arm. Its actions vary according to the position of the upper limb and the fibers recruited.

Latissimus Dorsi

The latissimus dorsi contributes to adduction, extension, and medial rotation of the humerus. It is particularly important during movements that pull the upper limb downward or toward the trunk.

Teres Major

Teres major assists adduction and medial rotation of the humerus and can contribute to extension from a flexed position.

Major Shoulder Adductors

Muscle	Relevant Actions
Pectoralis major	Adduction and medial rotation
Latissimus dorsi	Adduction, extension, and medial rotation
Teres major	Adduction and medial rotation

Hip Abduction

Hip abduction moves the thigh away from the median plane. It is produced primarily by muscles on the lateral side of the hip.

The gluteus medius and gluteus minimus are major hip abductors, with assistance from the tensor fasciae latae.

Gluteus Medius

The gluteus medius is a major abductor of the hip. Its functional importance is particularly evident during single-limb support, when it helps stabilize the pelvis.

Gluteus Minimus

The gluteus minimus lies deep to the gluteus medius and contributes to hip abduction and pelvic stabilization.

Tensor Fasciae Latae

The tensor fasciae latae contributes to hip abduction and acts through the iliotibial tract to influence lateral stability of the lower limb.

Major Hip Abductors

Muscle	Major Role
Gluteus medius	Hip abduction and pelvic stabilization
Gluteus minimus	Hip abduction and pelvic stabilization
Tensor fasciae latae	Assists hip abduction and contributes to lateral stabilization

Hip Abductors During Walking

During single-limb support in gait, the hip abductors of the stance limb contract to control the pelvis. Without sufficient abductor force, the unsupported side of the pelvis tends to drop.

This illustrates that a muscle can perform an important functional role even when obvious abduction of the limb is not occurring.

Trendelenburg Sign

A positive Trendelenburg sign may occur when the hip abductors of the stance limb are weak or their nerve supply is impaired. The pelvis drops on the unsupported side because the stance-side abductors cannot adequately stabilize it.

Hip Adduction

Hip adduction moves the thigh toward the median plane. The principal adductors occupy the medial compartment of the thigh.

Adductor Longus

The adductor longus contributes strongly to adduction of the thigh and can participate in other hip movements depending on joint position.

Adductor Brevis

The adductor brevis lies deep to portions of the adductor longus and contributes to hip adduction.

Adductor Magnus

The adductor magnus is a large muscle with extensive attachments. Its adductor portion contributes strongly to hip adduction, while its hamstring portion has an important role in hip extension.

Gracilis

The gracilis is a long medial thigh muscle that crosses both the hip and knee. It contributes to hip adduction and also acts at the knee.

Pectineus

The pectineus contributes to adduction and flexion of the thigh and occupies the proximal medial region of the thigh.

Major Hip Adductors

Muscle	Relevant Action
Adductor longus	Adduction of thigh
Adductor brevis	Adduction of thigh
Adductor magnus	Powerful adduction, with region-specific additional actions
Gracilis	Adduction of thigh and action at knee
Pectineus	Adduction and flexion of thigh

Finger Abduction and Adduction

The terminology for finger movement uses the middle finger as the reference axis rather than the median plane of the entire body.

Finger abduction spreads the digits away from the axis of the middle finger, while adduction brings them toward that axis.

Middle Finger as the Reference Axis

Because the middle finger defines the reference axis, it can abduct in either direction away from its own central position. It does not have a comparable adduction movement toward itself.

Dorsal Interossei

The dorsal interossei abduct the fingers at the metacarpophalangeal joints. A common mnemonic is DAB, meaning dorsal interossei abduct.

Palmar Interossei

The palmar interossei adduct the fingers toward the middle finger. A common mnemonic is PAD, meaning palmar interossei adduct.

Finger Abduction and Adduction Muscles

Movement	Primary Muscles	Reference
Abduction	Dorsal interossei, with abductor digiti minimi for the little finger	Away from middle finger axis
Adduction	Palmar interossei	Toward middle finger axis

Thumb Abduction and Adduction

The thumb is oriented differently from the other digits because of rotation during development and the specialized configuration of the first carpometacarpal joint.

Thumb abduction and adduction therefore occur in planes that differ from the corresponding movements of digits two through five.

Thumb Abduction

Abduction of the thumb moves it anteriorly away from the plane of the palm. Important muscles include the abductor pollicis brevis and abductor pollicis longus.

Thumb Adduction

Adduction returns the thumb toward the plane of the palm. The adductor pollicis is the principal muscle responsible for this movement.

Toe Abduction and Adduction

For the toes, movements are described relative to the axis of the second toe. Abduction moves the toes away from the second toe, while adduction moves them toward it.

Dorsal Interossei of the Foot

The dorsal interossei abduct toes two through four relative to the second-toe axis.

Plantar Interossei

The plantar interossei adduct toes three through five toward the second toe.

Great Toe Movements

The abductor hallucis abducts the great toe away from the second toe, while the adductor hallucis draws the great toe toward the second toe.

Digit Reference Axes

Region	Reference Axis	Abduction	Adduction
Fingers	Middle finger	Away from middle finger	Toward middle finger
Toes	Second toe	Away from second toe	Toward second toe

Abduction at the Wrist

Movement of the hand toward the radial side at the wrist is commonly called radial deviation. It can also be described as abduction of the wrist.

Radial Deviation

Radial deviation is produced by coordinated action of wrist flexors and extensors located on the radial side, particularly the flexor carpi radialis and extensor carpi radialis muscles.

Adduction at the Wrist

Movement of the hand toward the ulnar side is called ulnar deviation and can also be described as adduction of the wrist.

Ulnar Deviation

Flexor carpi ulnaris and extensor carpi ulnaris cooperate to produce ulnar deviation while their opposing flexion and extension actions partially balance one another.

Wrist Terminology

Anatomical Movement	Common Wrist Term
Abduction	Radial deviation
Adduction	Ulnar deviation

Abduction of the Scapula

Movement of the scapula away from the vertebral column around the thoracic wall is often called protraction rather than abduction. Serratus anterior is a major muscle producing this movement.

Adduction of the Scapula

Movement of the scapula toward the vertebral column is commonly called retraction. The middle fibers of trapezius and the rhomboid muscles are important contributors.

Abduction and Adduction in Closed Kinetic Chains

Abduction and adduction do not always involve a freely moving distal limb. When the distal segment is fixed, muscular actions can move or stabilize the pelvis, trunk, or other proximal structures.

Hip abductor function during single-leg stance is an important example.

Open-Chain Hip Abduction

When the foot is free, contraction of the hip abductors can move the femur away from the median plane. This is an open-chain action.

Closed-Chain Hip Abductor Function

When the foot is fixed on the ground, the same muscles can act on the pelvis rather than moving the femur freely. During walking, they help prevent excessive pelvic drop on the unsupported side.

Open-Chain Hip Adduction

With the distal limb free, the hip adductors move the femur toward the body's median plane.

Closed-Chain Adductor Function

When the lower limb is fixed, adductor muscles can contribute to control of the pelvis and femur and participate in multidirectional stabilization.

Range of Motion

The available range of abduction and adduction varies among joints and individuals. It is influenced by joint geometry, capsular and ligamentous restraints, muscle extensibility, body position, age, injury, and other anatomical factors.

Joint Position and Muscle Action

A muscle's ability to generate abduction or adduction torque depends on its line of pull relative to the joint axis. Changes in joint position can alter moment arms and therefore alter the mechanical contribution of individual muscles.

Muscle Moment Arms

A muscle produces rotational force around a joint when its line of action passes at a perpendicular distance from the joint axis. This distance is the moment arm.

Changes in the moment arm throughout a joint's range can influence how effectively a muscle produces abduction or adduction.

Gravity and Abduction

When a limb is abducted against gravity, the abductor muscles must generate sufficient torque to overcome the gravitational moment acting on the limb.

The muscular demand generally changes as the position of the limb alters the gravitational moment arm.

Gravity and Adduction

Returning an abducted limb toward the body may be assisted by gravity depending on body position. Muscles can act eccentrically to control this movement rather than simply allowing the limb to fall.

Concentric Abduction

During concentric contraction, an abductor shortens while generating force, such as when the deltoid raises the arm laterally against gravity.

Eccentric Abductor Action

An abductor can also lengthen while producing force. For example, shoulder abductors can act eccentrically to control lowering of the arm from an abducted position.

Isometric Abductor Action

During an isometric contraction, the muscle produces force without substantial change in overall length. Hip abductors can act approximately isometrically to stabilize the pelvis during portions of single-limb support.

Abduction and Adduction During Gait

Although walking occurs predominantly in the sagittal plane, frontal-plane control is essential. Hip abductors and adductors regulate lateral movement of the pelvis and femur and contribute to efficient transfer of body weight between limbs.

Pelvic Stability

The stance-side hip abductors generate a moment that counteracts the tendency of body weight to rotate the pelvis downward on the unsupported side.

Frontal-Plane Knee Control

Movements of the hip and pelvis influence alignment of the femur and knee during weight-bearing tasks. Hip muscle control therefore contributes indirectly to frontal-plane mechanics at more distal joints.

Abduction and Adduction During Running

Running increases the magnitude and rate of forces that must be controlled during single-limb support. Coordinated hip abductor and adductor activity contributes to pelvic and lower limb control.

Abduction and Adduction During Side-Stepping

Side-stepping requires repeated hip abduction and adduction as the body moves laterally. The abductors generate and control lateral movement while the adductors assist in repositioning the limbs and controlling momentum.

Abduction and Adduction in Upper Limb Function

Shoulder abduction positions the hand away from the trunk and increases the reachable workspace of the upper limb. Adduction returns the arm toward the body or generates force during pulling movements.

Overhead Movement

Overhead reaching requires coordinated humeral elevation, scapular upward rotation, clavicular movement, and stabilization of the glenohumeral joint.

Clinical Examination of Shoulder Abduction

Shoulder abduction can be assessed through active range of motion, passive range of motion, and resisted muscle testing. The examiner may evaluate pain, weakness, movement quality, scapular motion, and asymmetry.

Axillary Nerve and Abduction

The axillary nerve supplies the deltoid and teres minor. Injury to the axillary nerve can impair deltoid function and weaken shoulder abduction.

Suprascapular Nerve and Abduction

The suprascapular nerve supplies the supraspinatus and infraspinatus. Dysfunction can weaken initiation and assistance of shoulder abduction and impair rotator cuff function.

Long Thoracic Nerve and Arm Elevation

The long thoracic nerve supplies serratus anterior. Injury can produce scapular winging and impair upward rotation of the scapula, making full elevation of the upper limb difficult.

Clinical Examination of Hip Abduction

Hip abduction strength is commonly tested against resistance. Pelvic control during single-leg stance also provides functional information about the hip abductor mechanism.

Superior Gluteal Nerve

The superior gluteal nerve supplies gluteus medius, gluteus minimus, and tensor fasciae latae. Injury can impair hip abduction and pelvic stabilization.

Clinical Examination of Hip Adduction

Hip adduction can be tested by asking the individual to move the thigh toward the midline against resistance. Most major adductors are supplied primarily by the obturator nerve, although individual muscles can have additional or different innervation.

Obturator Nerve

The obturator nerve is closely associated with the medial compartment of the thigh. Injury can produce weakness of thigh adduction and sensory changes in its cutaneous distribution when relevant fibers are affected.

Finger Abduction Testing

Finger abduction can be assessed by asking the person to spread the fingers against resistance. This tests the dorsal interossei and provides useful information about ulnar nerve function.

Finger Adduction Testing

Finger adduction can be assessed by asking the person to hold the fingers together against resistance. The palmar interossei are also supplied by the ulnar nerve.

Abduction and Adduction Injuries

Muscles responsible for abduction and adduction can be affected by strains, tendon disorders, nerve injuries, joint pathology, and traumatic instability.

The functional consequences depend on the joint and the specific structures involved.

Groin Strain

A groin strain commonly involves injury to one or more hip adductor muscles or their musculotendinous attachments. It may occur during rapid directional changes, kicking, or forceful lateral movements.

Rotator Cuff Dysfunction

Pathology affecting the supraspinatus or other rotator cuff structures can produce pain or weakness during shoulder abduction and alter normal glenohumeral mechanics.

Abductor Weakness

Weakness of an abductor group can affect much more than the ability to move a limb laterally. At the hip, for example, abductor weakness can compromise pelvic stability during walking.

Adductor Weakness

Weakness of adductor muscles can reduce the ability to generate medial force and control lateral movement of the limb. Functional effects vary according to activity and associated muscle function.

Abduction and Adduction Contractures

Persistent shortening of muscles, capsules, or other soft tissues can hold a joint in an abducted or adducted position and restrict movement in the opposite direction.

Abduction and Adduction in Anatomical Description

These terms provide a standardized way to describe movement without relying on the observer's perspective. Their meaning is based on anatomical reference planes and axes.

Important Exceptions and Special Uses

Region	Special Consideration
Fingers	Middle finger is reference axis
Toes	Second toe is reference axis
Thumb	Orientation causes abduction and adduction to occur differently from other digits
Wrist	Abduction and adduction commonly called radial and ulnar deviation
Scapula	Comparable movements usually termed protraction and retraction

Functional Examples

Activity	Movement
Raising arm sideways	Shoulder abduction
Lowering arm toward trunk	Shoulder adduction
Moving leg sideways	Hip abduction
Bringing legs together	Hip adduction
Spreading fingers	Finger abduction
Bringing fingers together	Finger adduction
Moving hand toward thumb side	Radial deviation or wrist abduction
Moving hand toward little-finger side	Ulnar deviation or wrist adduction

Key Anatomical Features

Feature	Key Point
Abduction	Movement away from median plane or reference axis
Adduction	Movement toward median plane or reference axis
Primary plane	Frontal plane
Primary axis	Anteroposterior axis
Major shoulder abductors	Supraspinatus and deltoid
Major shoulder adductors	Pectoralis major, latissimus dorsi, teres major
Major hip abductors	Gluteus medius, gluteus minimus, tensor fasciae latae
Major hip adductors	Adductor longus, brevis, magnus, gracilis, pectineus
Finger reference	Middle finger
Toe reference	Second toe

Anatomical and Functional Importance

Abduction and adduction describe fundamental patterns of movement that occur throughout the musculoskeletal system. Although their general definitions refer to movement away from and toward the median plane, specialized reference axes are used for the fingers and toes.

At the shoulder and hip, these movements depend on coordinated muscle forces, joint geometry, capsular and ligamentous restraints, and stabilization of neighboring body segments. Shoulder abduction requires not only movement of the humerus but also coordinated scapular rotation, while hip abductor activity is essential for stabilizing the pelvis during single-limb support.

The same muscles can perform different functional roles depending on whether the distal segment is free or fixed. Abductors and adductors may move a limb in open-chain activity or stabilize and control the pelvis and trunk during weight-bearing activity.

Abduction and adduction therefore provide an important framework for understanding joint motion, muscle actions, frontal-plane biomechanics, gait, postural stability, clinical muscle testing, peripheral nerve function, and coordinated human movement.