American Board of Internal Medicine (ABIM) Certification Practice Exam

The test characterized by pain with active shoulder abduction and a positive painful arc is strongly indicative of supraspinatus tendinitis. This phenomenon occurs because the supraspinatus tendon passes beneath the acromion during shoulder abduction. As the arm is lifted above shoulder level, the tendon can become compressed between the acromion and the humeral head, leading to pain. This painful arc is typically observed between 60 and 120 degrees of abduction, where patients report significant discomfort, but the pain often resolves when their arm is at rest or below this range of motion. The presence of this specific pain pattern helps to differentiate supraspinatus tendinitis from other shoulder conditions. While subacromial bursitis can also present with similar symptoms, especially given its association with the same anatomical structures, the hallmark of active abduction pain combined with a painful arc is particularly representative of supraspinatus tendinitis. Conversely, conditions like a rotator cuff tear or shoulder instability manifest with different symptom patterns and do not distinctly feature the painful arc.