Differential Diagnosis for Lateral Shoulder Pain
Single Most Likely Diagnosis
- Rotator Cuff Tendinitis: This is the most common cause of lateral shoulder pain, often resulting from overuse or repetitive strain on the rotator cuff muscles and tendons. Activities that involve lifting, throwing, or repetitive arm movements can lead to inflammation and pain.
Other Likely Diagnoses
- Subacromial Bursitis: Inflammation of the subacromial bursa, which reduces friction between the rotator cuff and the acromion, can cause lateral shoulder pain. It often occurs in conjunction with rotator cuff tendinitis.
- Lateral Epicondylitis (Tennis Elbow): Although more commonly associated with elbow pain, lateral epicondylitis can radiate pain to the lateral aspect of the shoulder due to referred pain patterns.
- Adhesive Capsulitis (Frozen Shoulder): Characterized by stiffness and pain in the shoulder joint, adhesive capsulitis can present with lateral shoulder pain, especially in the early stages.
Do Not Miss Diagnoses
- Fracture (e.g., Humeral Neck Fracture): While less common, a fracture in the shoulder region can cause severe lateral shoulder pain and must be ruled out, especially in the context of trauma or a fall.
- Septic Arthritis or Osteomyelitis: Infection within the shoulder joint or bone can cause severe pain, redness, and swelling. These conditions are medical emergencies requiring prompt diagnosis and treatment.
- Referred Pain from Cardiac or Pulmonary Sources: In rare cases, lateral shoulder pain can be referred from cardiac (e.g., myocardial infarction) or pulmonary (e.g., pulmonary embolism) conditions. These are critical diagnoses that must not be missed.
Rare Diagnoses
- Osteonecrosis of the Humeral Head: A condition where the blood supply to the humeral head is interrupted, leading to bone death and potentially causing shoulder pain.
- Tumors (Benign or Malignant): Although rare, tumors affecting the shoulder region can cause lateral shoulder pain. Examples include osteoid osteoma, osteosarcoma, or metastatic disease.
- Neurological Causes (e.g., Radiculopathy, Neuropathy): Certain neurological conditions affecting the nerves that supply the shoulder can cause pain in the lateral shoulder area. These might include cervical radiculopathy or peripheral neuropathy.