Differential Diagnosis

The patient's symptoms of constant low-level pain, a slipping feeling, and severe pain with exertion suggest a musculoskeletal issue, likely related to the joint. Here's a categorized differential diagnosis:

• Single most likely diagnosis

  • Shoulder Instability: This condition, where the shoulder joint is prone to slipping out of place, matches the patient's symptoms closely. The feeling of the joint coming out of the socket and the exacerbation of pain with exertion are characteristic.

• Other Likely diagnoses

  • Rotator Cuff Tendinopathy: Inflammation or irritation of the tendons surrounding the shoulder joint can cause pain, especially with exertion, and might contribute to a feeling of instability.
  • Labral Tear: A tear in the labrum, the cartilage that surrounds the socket of the shoulder joint, can cause pain and a sense of instability, especially with movement.
  • Osteoarthritis: While more common in older populations, osteoarthritis of the shoulder can cause chronic pain and stiffness, potentially worsening with exertion.

• Do Not Miss

  • Septic Arthritis: Although less likely, an infection within the joint can cause severe pain, especially with movement, and must be considered due to its potential for rapid joint destruction and systemic infection.
  • Fracture: A fracture, especially a stress fracture or an occult fracture not immediately visible on initial X-rays, could cause severe pain with exertion and must be ruled out.

• Rare diagnoses

  • Adhesive Capsulitis (Frozen Shoulder): While it primarily causes stiffness and limited range of motion, in its early stages, it can present with pain, especially at night or with exertion.
  • Neoplastic Processes: Tumors, either benign or malignant, within the bone or soft tissues around the joint, are rare but could cause persistent pain and other symptoms, depending on their location and size.