Differential Diagnosis for Rotator Cuff Tendonitis vs. Bicipital Tendonitis

When attempting to distinguish between rotator cuff tendonitis and bicipital tendonitis, it's crucial to consider the symptoms, physical examination findings, and sometimes, diagnostic imaging. Here's a structured approach to the differential diagnosis:

• Single Most Likely Diagnosis:

  • Rotator Cuff Tendonitis: This is often the most common condition affecting the shoulder, leading to pain and limited mobility. The justification for this being the single most likely diagnosis lies in its prevalence and the fact that symptoms such as pain over the lateral aspect of the shoulder, especially at night, and weakness in abduction are very common.

• Other Likely Diagnoses:

  • Bicipital Tendonitis: This condition involves inflammation of the tendon of the long head of the biceps brachii muscle and can present with anterior shoulder pain, especially with activities involving forward elevation or rotation of the arm. The proximity of the biceps tendon to the rotator cuff tendons and the overlap in symptomatology make it a likely consideration.
  • Adhesive Capsulitis (Frozen Shoulder): This condition can mimic rotator cuff tendonitis in its early stages, presenting with pain and stiffness. However, it typically progresses to significant limitation in range of motion.
  • Subacromial Bursitis: Inflammation of the subacromial bursa can cause symptoms similar to rotator cuff tendonitis, including pain with overhead activities.

• Do Not Miss Diagnoses:

  • Rotator Cuff Tear: While this might seem like an extension of tendonitis, a full-thickness tear can have significantly different management and prognosis. Missing this diagnosis could lead to prolonged disability and potentially necessitate more invasive treatments if not addressed promptly.
  • Shoulder Instability: Anterior or multidirectional instability can cause chronic pain and apprehension, mimicking tendonitis. Missing this could lead to inappropriate treatment and potential for further injury.
  • Neer's Phase III Impingement: This represents a more advanced stage of shoulder impingement where there is a fixed loss of motion and potentially a rotator cuff tear, which would require more aggressive management.

• Rare Diagnoses:

  • Calcific Tendonitis: This condition involves the deposition of calcium within the tendons of the rotator cuff, leading to acute, severe pain. It's less common but can be very painful and may require specific treatment.
  • Inflammatory Arthritis (e.g., Rheumatoid Arthritis): Although less common as a primary presentation in the shoulder, inflammatory arthritides can cause shoulder pain and stiffness, mimicking tendonitis.
  • Septic Arthritis or Osteomyelitis: These are rare but serious conditions that could present with shoulder pain and must be considered, especially in patients with fever, significant swelling, or systemic symptoms.