Differential Diagnosis for Anterior Shoulder Pain
Single most likely diagnosis
- Subscapularis strain or tendinopathy: The patient's symptoms of worsening anterior shoulder pain, especially with posterior and internal flexion and rotation, are consistent with a subscapularis injury. The subscapularis muscle is one of the rotator cuff muscles that helps stabilize the shoulder joint and assists in internal rotation and adduction. The fact that pain is exacerbated by movements that engage these actions supports this diagnosis.
Other Likely diagnoses
- Bicipital tendinitis: The pain extending down what feels like the biceps, especially with movements that involve pushing down or laterally across the body, could indicate bicipital tendinitis. This condition involves inflammation of the tendon that attaches the biceps muscle to the shoulder joint.
- Anterior shoulder instability: The patient's left hand dominance and the nature of the pain could also suggest anterior shoulder instability, where the shoulder joint is prone to slipping out of place, especially with certain movements.
- Rotator cuff strain: Given the patient's recent activity (long bike ride), a strain to the rotator cuff muscles or tendons is possible, leading to pain with specific movements.
Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Thoracic outlet syndrome: Although less likely, thoracic outlet syndrome could cause shoulder pain and must be considered due to its potential for serious complications, including nerve damage or vascular compromise.
- Cardiac referral pain: It's crucial to rule out cardiac issues, as shoulder pain can sometimes be referred from the heart, especially if the pain is acute and severe.
Rare diagnoses
- Quadrilateral space syndrome: This is a rare condition that involves compression of the axillary nerve and/or posterior circumflex humeral artery, leading to shoulder pain and potentially weakness.
- Suprascapular nerve entrapment: This condition involves compression of the suprascapular nerve and can cause shoulder pain, especially with movements that involve the rotator cuff muscles.