The rotator cuff comprises four muscles and their tendons, the supraspinatus, infraspinatus, teres minor, and subscapularis. Rotator cuff tears (RCTs) are common and most frequently involve the supraspinatus, and usually occur through tendon rather than muscle. Clinical manifestations vary depending on the size and age of the tear, the individual's physical demands, psychosocial factors, and other variables; tears may range from the asymptomatic to large, full-thickness, and retracted tears that cause pain, weakness, and at least partial disability. Individuals involved in rear-end motor vehicle collisions (MVCs) may complain of “shoulder” pain, and magnetic resonance imaging may reveal the presence of shoulder cuff tears, high-energy trauma can cause rotator cuff tears, but the tensile forces encountered in rear-end MVCs almost certainly do not cause rotator cuff tears de novo. Because rear-end collisions and RCTs are common and often involve claims or lawsuits, physicians may be asked to assess the causation of the RCTs. Treatment should be based on clinical findings and not the results of imaging; the same applies to causation analysis: Involvement in a rear-end MVC does not establish causality for a rotator cuff tear. The medical literature is devoid of evidence indicating that rear-end collisions cause RCTs, but compelling evidence in the biomechanical literature shows that low-speed rear-end MVCs do not cause RCTs.