Differential Diagnosis for MSK Causes of Si Joint Pain Radiating into L Hip/Groin

• Single Most Likely Diagnosis
  • Sacroiliac (SI) joint dysfunction or inflammation: This is the most likely diagnosis due to the direct involvement of the SI joint and the common referral pattern of pain into the lower hip and groin area.
• Other Likely Diagnoses
  • Piriformis syndrome: The piriformis muscle runs from the base of the spine to the thighbone, and its irritation can cause pain in the SI joint area that radiates into the hip and groin.
  • Trochanteric bursitis: Inflammation of the bursa over the trochanter (a bony prominence on the outside of the hip) can cause pain that radiates into the hip and groin.
  • Osteitis pubis: Inflammation of the pubic bone and its surrounding structures can cause pain in the groin area that may radiate to the hip.
• Do Not Miss Diagnoses
  • Avulsion fracture of the iliac crest or ischial tuberosity: Although less common, these fractures can cause significant pain and disability if not promptly diagnosed and treated.
  • Stress fracture of the sacrum or pubic rami: Stress fractures in these areas can be difficult to diagnose but are critical to identify due to their potential for complications if left untreated.
  • Inflammatory spondyloarthropathies (e.g., ankylosing spondylitis): These conditions can cause SI joint pain and stiffness, and early diagnosis is crucial for effective management.
• Rare Diagnoses
  • Sacral insufficiency fracture: A type of stress fracture that occurs in the sacrum, often in individuals with osteoporosis or other underlying bone health issues.
  • Neoplastic processes (e.g., metastatic disease, primary bone tumors): Although rare, tumors can cause pain in the SI joint area that radiates into the hip and groin, making them an important consideration in the differential diagnosis.