Differential Diagnosis for Pain in R Bicep/Tricep and Posterior Shoulder

Single Most Likely Diagnosis

• Muscle Strain: The most common cause of pain in the bicep, tricep, and posterior shoulder after lifting, due to overstretching or tearing of the muscle fibers. The history of lifting something heavy 1 week ago supports this diagnosis.

Other Likely Diagnoses

• Tendinitis: Inflammation of the tendons surrounding the shoulder joint, which can occur due to repetitive strain or acute injury from lifting. This could affect the bicep or tricep tendons.
• Rotator Cuff Strain: The rotator cuff muscles and tendons can be strained during heavy lifting, leading to pain in the posterior shoulder and potentially radiating to the bicep or tricep areas.
• Bursitis: Inflammation of the bursae, fluid-filled sacs that cushion joints and reduce friction, can cause pain in the shoulder region, including the posterior aspect and potentially affecting the bicep and tricep areas.

Do Not Miss Diagnoses

• Thoracic Outlet Syndrome: Although less likely, 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), which can cause pain in the shoulder, arm, and potentially the bicep and tricep areas. Missing this diagnosis could lead to prolonged nerve compression and potential permanent damage.
• Myocardial Infarction (MI) or Cardiac Ischemia: It is crucial to consider cardiac causes of arm pain, especially if the pain is severe, radiates, or is accompanied by other symptoms like chest pain, shortness of breath, or nausea. Although the history provided does not strongly suggest a cardiac cause, it is always important to rule out MI, especially in patients with risk factors.

Rare Diagnoses

• Rhabdomyolysis: A serious syndrome due to direct or indirect muscle injury, which results in the death of muscle fibers and release of their contents into the bloodstream. This could be a rare complication of extreme muscle strain from lifting.
• Neoplastic Processes: Tumors affecting the bone, muscle, or nerve tissue in the shoulder or arm could cause pain but would be much less common and typically associated with other symptoms like unexplained weight loss or night pain.