Pectoralis Major Tear

The pectoralis major is a fan-shaped muscle with two heads. The clavicular head originates at the medial two thirds of the clavicle, while the larger stenral head originates at the anterior manubrium, sternum, and the cartilage of the first 6 ribs. The two heads insert at the lateral lip of the bicipital groove of the humerus.

Tears of the pectoralis major muscle can occur in the muscle (usually due to direct trauma), at the myotendinous junction (most common), or at the tendinous insertion. Tears are classically seen in weightlifters.

Partial tears are more common and tend to occur at the myotendinous junction. Complete tears, on the other hand, tend to occur at the tendon-bone interface. Sternal head tears are more common, but clavicular head tears occur as frequently as sternal head tears in elderly patients.

Here we see a large partial tear of the myotendinous junction of the sternal head of the pectoralis major muscle on fluid-sensitive sequences (from top to bottom: axial, sagittal, and coronal).

References

Connell DA, Potter HG, Sherman MF, Wickiewicz TL. Injuries of the pectoralis major muscle: evaluation with MR imaging. Radiology. 1999 Mar;210(3):785-91.