A 35-year-old professional swimmer presents to the clinic with a 3-week history of right shoulder pain. He notes that the pain is most severe when he is reaching overhead during his freestyle stroke and when he is reaching for his seatbelt while driving. He denies any acute trauma or weakness, but the pain often keeps him from sleeping on his right side. Past medical history is negative. Vital signs are within normal limits. On physical examination, there is no visible atrophy of the shoulder girdle. There is subacromial tenderness to palpation. Passive abduction of the arm to 90° followed by internal rotation produces significant pain at the anterior shoulder. Strength is 5/5 in abduction, internal rotation, and external rotation, although testing is limited by discomfort.
Which of the following is the most likely diagnosis?
The correct answer is:
D) Rotator cuff tendonitis
The patient is presenting with rotator cuff tendonitis, also known as subacromial impingement syndrome. This is an overuse injury common in athletes or workers who perform repetitive overhead motions. The pathophysiology involves the impingement of the rotator cuff tendons (most commonly the supraspinatus) as they pass through the narrow subacromial space beneath the acromion and the coracoacromial ligament. Chronic repetitive friction leads to inflammation, edema, and microtears within the tendon. The clinical hallmark is impingement pain, which is specifically triggered by reaching overhead or lifting the arm out to the side. The physical exam maneuvers described, specifically the Hawkins-Kennedy test (internal rotation at 90° of flexion) and the Neer test (passive forward flexion), are designed to provoke this impingement. A key feature that distinguishes tendonitis from a rotator cuff tear is the preservation of strength. While the patient may have pain-limited weakness, the actual integrity of the muscle-tendon unit remains intact.
Answer choice A: Adhesive capsulitis, is incorrect. Also known as frozen shoulder, adhesive capsulitis presents with a global, significant loss of both active and passive range of motion. This patient, however, presents with pain during specific maneuvers rather than a generalized restriction of joint movement.
Answer choice B: Bicipital tendonitis, is incorrect. Bicipital tendonitis typically causes pain localized strictly to the anterior bicipital groove. It is aggravated by resisted elbow flexion or forearm supination rather than the subacromial impingement maneuvers seen here.
Answer choice C: Rotator cuff tear, is incorrect. While the symptoms are similar, a key feature that distinguishes tendonitis from a tear is the preservation of strength. While this patient has pain-limited weakness, his actual strength is 5/5, indicating the muscle-tendon unit remains mechanically intact.
Answer choice E: Subacromial bursitis, is incorrect. Although subacromial bursitis often coexists with rotator cuff tendonitis as part of the same impingement spectrum, primary tendon pathology is the more definitive diagnosis when the symptoms are directly related to repetitive athletic use.
Key Learning Point
Rotator cuff tendonitis is an inflammatory condition caused by the impingement of the supraspinatus tendon under the acromial arch. It presents with subacromial pain during overhead activity and a positive impingement sign on exam. Unlike a full-thickness rotator cuff tear, strength is preserved. Initial management is conservative, focusing on activity modification, physical therapy for scapular stabilization, and NSAIDs.
