Differential Diagnosis for Shoulder Pain
The patient presents with shoulder pain primarily at the acromioclavicular (AC) joint, a perceived sensation of weakness, and no recent trauma, with symptoms slowly worsening over time. The differential diagnosis can be categorized as follows:
Single Most Likely Diagnosis
- AC Joint Arthritis or Osteoarthritis: This condition is a common cause of shoulder pain localized to the AC joint, especially in middle-aged individuals. The gradual worsening of symptoms without a history of trauma supports this diagnosis, as osteoarthritis tends to progress over time due to wear and tear of the joint.
Other Likely Diagnoses
- Rotator Cuff Tendinopathy or Tear: Although the pain is primarily at the AC joint, rotator cuff issues can sometimes refer pain to this area. The perceived weakness could be due to pain limiting movement or actual muscle weakness from a tear.
- Bursitis (Subacromial or Subdeltoid): Inflammation of the bursae around the shoulder can cause pain and weakness, especially if the bursitis is severe enough to limit movement.
- Adhesive Capsulitis (Frozen Shoulder): This condition can cause pain and significant stiffness in the shoulder, leading to a sensation of weakness due to limited mobility.
Do Not Miss Diagnoses
- Referred Pain from Cervical Spine: Cervical spine disorders, such as herniated discs or cervical spondylosis, can refer pain to the shoulder area. Missing a cervical spine issue could lead to delayed diagnosis and inappropriate treatment.
- Thoracic Outlet Syndrome: This condition involves compression of the nerves and/or blood vessels that pass into the thoracic outlet (the space between your collarbone and first rib). It can cause shoulder pain, weakness, and other symptoms in the arm.
- Pancoast Tumor: A rare type of lung cancer that can cause shoulder pain due to local invasion of the tumor into the brachial plexus or ribs. Although rare, it's critical not to miss this diagnosis due to its severe implications.
Rare Diagnoses
- Polymyalgia Rheumatica: An inflammatory condition that causes muscle pain and stiffness, typically in the shoulders and hips. It's more common in older adults but could be considered in this age group.
- Septic Arthritis of the AC Joint: A rare but serious infection within the joint that requires prompt diagnosis and treatment to prevent joint destruction.
- Osteonecrosis of the Clavicle: A rare condition where the blood supply to the clavicle is interrupted, leading to bone death. It could cause pain at the AC joint but is less common than other causes of shoulder pain.