Lateral attachment

The terms medial and lateral attachments describe the relative positions of a muscle’s attachment sites in relation to the body’s midline. These terms are particularly useful for muscles of the trunk and neck, where movement occurs in the transverse or coronal planes.

• Medial attachment: The site of attachment closer to the midline of the body. It often serves as the more fixed or less mobile point during contraction.

• Lateral attachment: The site of attachment farther from the midline of the body. It is usually the more mobile point during contraction.

Example

Pectoralis major muscle

• Medial attachment: Medial half of the clavicle, sternum, and costal cartilages of ribs 1–6.

• Lateral attachment: Lateral lip of the intertubercular sulcus of the humerus.

Contraction pulls the humerus medially (adduction and internal rotation).

Summary

Medial attachments typically lie near the vertebral column or midline structures, while lateral attachments are positioned on the limbs or lateral parts of the thorax. During contraction, movement usually brings the lateral attachment toward the medial one.