As the weight is lowered to the chest, fibers originating from the sternal head are maximally stretched. This may be particularly true with rapidly changing muscle mass when a person uses anabolic steroids or growth hormone. The patient usually has no warning of impending rupture. In most cases there are no preceding complaints relating to pectoralis problems. The patient experiences an abrupt tearing sensation and pain in the affected arm and chest wall and may report hearing a pop when the injury occurs.
Physical examination demonstrates an obvious defect in the anterior axillary border.
Weakness in adduction, internal rotation, and flexion of the arm is universal. The patient will generally have limited ROM due to pain. Grade 1 and grade 2 injuries without significant tearing may produce local swelling and ecchymosis but no defect in the axillary border. Plain radiographs are not uniformly helpful but will often demonstrate an absence of the pectoralis shadow on the anterior chest wall. Determining the degree of tear may be difficult in the acute injury because of swelling, muscle spasm, and ecchymosis.