Scientists and health professionals rely on a standardized vocabulary of directional terms to describe the location and movement of structures within the human body. These terms, such as superior (toward the head) and inferior (toward the feet), establish a universal language for anatomy. All movement is referenced from the “anatomical position,” where the body stands upright, arms are at the sides, and the palms face forward. This fixed reference point is necessary to ensure consistent descriptions of how the body moves.
Movement Defined
Adduction is an anatomical movement defined as the motion of a limb or body part toward the midline of the body or the axis of an extremity. This movement occurs within the coronal plane, which divides the body into front and back sections. The term is derived from the Latin “ad-,” meaning toward, and “ducere,” meaning to draw or pull.
The concept of adduction is best understood in direct comparison to its opposing movement, which is abduction. Abduction involves moving a limb or part away from the midline, such as raising an arm straight out to the side. Conversely, adduction is the return motion, bringing the raised arm back down to rest against the side of the torso. This paired relationship ensures that every movement away from the body’s central axis has an equal and opposite action.
Application Across Major Joints
Adduction is a fundamental movement pattern seen across numerous joints in the body, consistently following the principle of moving toward the centerline. At the shoulder joint, adduction involves drawing the arm from an elevated or horizontal position back toward the side of the trunk. This action is common in movements like a chest fly exercise or dropping the arm after a wave.
In the lower body, adduction at the hip joint brings the leg toward or across the imaginary midline that splits the body vertically. This movement is responsible for actions such as squeezing the thighs together or bringing the legs back together after stepping out to the side. The hip is a ball-and-socket joint.
The fingers and toes also exhibit adduction, although the reference point shifts from the body’s main midline to the centerline of the hand or foot. Adduction in the hand means bringing the fingers together, moving them toward the middle finger. For the foot, adduction is the motion that draws the toes closer together toward the second toe.
Key Adductor Muscle Groups
The action of adduction is generated by specific muscle groups that primarily run along the medial, or inner, aspect of the limbs. In the upper body, adduction of the arm at the shoulder is mainly performed by two large muscles: the pectoralis major and the latissimus dorsi. The pectoralis major is a broad muscle on the chest, while the latissimus dorsi is a large muscle on the back. Both work together to pull the arm toward the body.
In the thigh, adduction is performed by a distinct set of five muscles collectively known as the adductor group, located in the medial compartment. This group includes:
- Adductor longus
- Adductor brevis
- Adductor magnus
- Pectineus
- Gracilis
These muscles originate on the pelvis (the pubis and ischium) and mostly insert along the back of the femur, or thigh bone.
The largest and most complex muscle in this group is the adductor magnus, which functions as both an adductor and a hamstring muscle. The gracilis is unique among the group because it is the only one that crosses both the hip and the knee joints, attaching below the knee on the tibia. The coordinated contraction of these muscles provides the necessary force to pull the legs inward.